and
toexplicitlymarkparagraphs.(Inthepreviousmethod,wehadjustusedCarriageReturnsandLineFeedstomarkthem.)Wemaywrite:Thisisthefirst,whichisimportant.
Inthetypesettinglanguageusedforwritingthisbook,mark-upisintroducedwiththebackslashescapecharacter,followedbyadescriptivenameofthechangebeingmade,withthecontentsenclosedincurlybrackets{and}:\section{SectionTitle}Thisisthe\textit{first}paragraph,whichis\textbf{important}.Here,wehaveused\section{}forthesectiontitle,\textit{}foritalic,and\textbf{}forbold.Thesedifferingmark-upsystemsarenotjusthistoricalartefacts:theyservedifferentpurposes.Therequirementsmaybewhollydifferentforadocumenttobeprinted,tobeputontheweb,ortobeviewedonaneBookreader.Wepromisedtotalkaboutrepresentingtheworld’smanylan-guagesandwritingsystems.Since1989,therehasbeenaninter-nationalindustrialeffort,undertheUnicodeinitiative,toencodemorethanonehundredthousandcharacters,givingeachanumber,anddefininghowtheymaybecombinedinvalidways.Therearemorethanamilliontotalslotsavailableforfutureuse.ItisimportanttosaythattheUnicodesystemisconcernedonlywithassigningcharacterstonumbers.Itdoesnotspecifytheshapesthosecharacterstake:thatisamatterfortypefacedesigners.Theprincipleisoneofseparationofconcerns:thateachpartofacom-putersystemshoulddoonejobwellandallowinteractionwiththeother,similarlywell-designedcomponents.ThisisparticularlydifficultfortheUnicodesystem,whichmustnavigateinnumerableculturaldifferencesandawidevarietyofpossibleuses.ThefollowingfivepagesgivesomeexamplesdrawnfromthehugeUnicodestandard. #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 104 Context: 90Chapter7.DoingSumsMuchbetter.Wecanmodifyourfunctioneasilytocalculatethesumofalistofnumbers:suml=ifl=[]then0elseheadl+sum(taill)sum[9,1,302]=⇒9+sum[1,302]=⇒9+(1+sum[302])=⇒9+(1+(302+sum[]))=⇒9+(1+(302+0))=⇒312Timeforsomethingalittlemoreambitious.Howmaywere-versealist?Forexample,wewantreverse[1,3,5,7]togive[7,5,3,1].Rememberthatweonlyhaveaccesstothefirstelementofalist(thehead),andthelistwhichitselfformsthetailofagivenlist–wedonothaveadirectwaytoaccesstheendofthelist.Thispreventsusfromsimplyrepeatedlytakingthelastelementofthelistandbuildinganewonewiththe•operator(which,yourecall,stickstwoliststogether).Well,wecanatleastwriteoutthepartfortheemptylist,sincereversingtheemptylistjustgivestheemptylist:reversel=ifl=[]then[]else...Ifthelistisnotempty,ithasaheadandatail.Wewanttomaketheheadgoattheendofthefinallist,andbeforethat,wewanttherestofthelist,itselfreversed.Sowewrite:reversel=ifl=[]then[]else[headl]•reverse(taill)Noticethatwewrote[headl]ratherthanjustheadlbecauseweneedtoturnitintoalistsothatthe•operatorcanwork.Letus #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 112 Context: # Chapter 8: Grey Areas When viewing the page from a normal reading distance, you can see that it is indeed possible. But how? The simplest method of converting a grey image into a black and white one is simply to pick a level of grey above which we consider each part of the image black and below which we consider it white. Here is our camel, printed using black ink for any part which is more than 50% black (i.e. a mid grey), and no ink for any part which is less than 50% black:  Well, we can see the shape of the camel, but the result is less than spectacular. Let's try moving the threshold to 40%:  We can’t see as much detail of the camel in this case, but at least its legs are solid. If we move the other way, to a threshold of 60%, things get even worse:  #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 16 Context: diamturpis,molestievitae,placerata,molestienec,leo.Maecenaslacinia.Namipsumligula,eleifendat,accumsannec,suscipita,ipsum.Morbiblanditligulafeugiatmagna.Nunceleifendconsequatlorem.Sedlacinianullavitaeenim.Pellentesquetinciduntpurusvelmagna.Integernonenim.Praesenteuismodnunceupurus.Donecbibendumquamintellus.Nullamcursuspulvinarlectus.Donecetmi.Namvulputatemetuseuenim.Vestibulumpellentesquefeliseumassa.102004006000200400600800xyYoucanseethatthechapterheading“Chapter1”beginsatabout(80,630).Noticethatthecoordinatesofthebottomleftofthepage(calledtheorigin)are,ofcourse,(0,0).Thechoiceofthebottomleftasouroriginissomewhatarbitrary–onecouldmakeanargumentthatthetopleftpoint,withverticalpositionsmeasureddownwards,isamoreappropriatechoice,atleastintheWestwherewereadtoptobottom.Ofcourse,onecouldalsohavetheoriginatthetoprightorbottomright,withhorizontalpositionsmeasuringleftward.Weshallbeusingsuchcoordinatestodescribethepositionandshapeofeachpartofeachletter,eachword,andeachparagraph,aswellasanydrawingsorphotographstobeplacedonthepage.Wewillseehowlinescanbedrawnbetweencoordinates,andhowtomaketheelegantcurveswhichformthelettersinatypeface.Oncewehavedeterminedwhatshapeswewishtoputoneachpage,wemustconsiderthefinalformofourdocument.Youmay #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 47 Context: Chapter3.StoringWords33f102t116e101p112space32h104,44y121a97e101space32"34l108space32"34Therearemanymorecharactersintheworldthanthese,andthereforemanyproprietaryandcompetingmethodsforextendingthistable.Theseincludetheadditionofaccentedcharactersinthewesternlanguages,andtheuseofothermethodsaltogetherfortheworld’sothercharactersets;forexample,theCyrilliccharactersofRussian,theHancharactersofChinese,andthemanywritingmethodsoflanguagesfromtheIndiansubcontinent.Weshallexaminesomeoftheselaterinthischapter.WehaveusedtheCarriageReturnandLineFeedcharacterstochangethewayourtextislaidout(sometimescalledformatting).However,wehavenotseenhowtochangethetypeface,typeshape,typethickness,orthesizeofthetext.Weshouldliketobeabletointro-ducesuchchangesduringtherunofthetext,asinthisparagraph.Whatisneededisawayto“markup”thetextwithannotationssuchas“makethiswordbold”or“changetotypesize8pthere”.Suchmethodsareknownasmark-uplanguages.Wecouldimagineasystemwheretyping,forexample,“This*word*mustbebold”intothecomputerwouldproduce“Thiswordmustbebold”ontheprintedpageorelectronicdocument.Wecoulduseasymbolforeachotherkindofchange–forexample,$foritalic–sowecanwrite“$awful$”andget“awful”.Aproblemarises,though.Whatifwewishtotypealiteral$character?Wemustescapetheclutchesofthespecialformattingsymbolstem-porarily.Wedosousingwhatiscalledanescapecharacter.Themostcommonis\(theso-calledbackslash).Wesaythatanycharacterim-mediatelyfollowingtheescapecharacteristoberenderedliterally.So,wecanwrite“And$especially$for\$10”toproduce“Andespeciallyfor$10”.Howthendowetypeabackslashitself?Well,thebackslashcanescapeitselfjustaswell!Wesimplywrite\\.So,theliteraltext“The\\character”produces“The\character”.Letuslookathowsomecommonmark-upsystemsrepresentthefollowingpieceofformattedtext:SectionTitleThisisthefirstparagraph,whichisimportant. #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 107 Context: Chapter7.DoingSums93Wecompare3with1.Toolarge.Wecompareitwiththesecond1.Toolarge.Wecompareitwith2,againtoolarge.Wecompareitwith3.Itisequal,sowehavefoundaplaceforit.Therestofthelistneednotbedealtwithnow,andthelistissorted.Hereisthewholeprograminoneplace:insertxl=ifl=[]then[x]elseifx≤headlthen[x]•lelse[headl]•insertx(taill)sortl=ifl=[]then[]elseinsert(headl)(sort(taill))Inthischapter,wehavecoveredalotofground,goingfromthemostsimplemathematicalexpressionstoacomplicatedcomputerprogram.Doingtheproblemsshouldhelpyoutofillinthegaps. #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 90 Context: # Chapter 6. Saving Space | Description | Image | |---------------------|----------------| | original – 100% |  | | 64 greys – 40% |  | | 8 greys – 14% |  | | 2 greys – 5% |  | **Figure A** | Description | Image | |---------------------|----------------| | all pixels |  | | 1/2 discarded |  | | 3/4 discarded |  | | 7/8 discarded |  | **Figure B** #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 15 Context: Chapter1PuttingMarksonPaperInthisbook,weshallneedverylittleformalmathematics,butifweareconsideringthearrangementoflettersandwordsandlinesandpicturesonthepage,weshallneedawayofdiscussingtheideaofposition–thatistosay,wheresomethingis,ratherthanjustwhatitis.Thankfully,ourpaperisflatandrectangular,sowecanusethesimplecoordinateswelearnedinschool.Inotherwords,wejustmeasurehowfarweareabovethebottomleftcornerofthepage,andhowfartotheright.Wecanwritethisasapairofnumbers;forexample,thecoordinate(6,2)issixlengthsright,andtwolengthsupfromthebottom-leftofthepage.Itisconventiontousextodenotetheacrosspartofthecoordinate,andytodenotetheuppart.TheseareknownasCartesiancoordinates,namedforRenéDescartes(1596–1659)–theLatinformofhisnameisRenatusCartesius,whichisalittlecloserto“Cartesian”.Theideawasdiscoveredindependently,ataboutthesametime,byPierredeFermat(1601–1665).Hereisthecoordinate(6,2)drawnonalittlegraph,withaxesforxandy,andlittlemarksontheaxestomakeiteasiertojudgepositionbyeye:012345670123xy(6,2)1 #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 120 Context: # Chapter 8. Grey Areas  It might surprise you that even the photographic process has trouble representing grey tones. Photographic film consists of particles of compounds of silver, suspended in a gel. When exposed to light, tiny changes to the crystal structure record an invisible image. When developed, each particle is either converted to silver (which will appear black in the final photograph), or not thus converted (which will appear white). The process of enlarging the photograph from the negative to the positive paper print may introduce greys by dint of its analogue nature, of course, but if enlarged enough, one can see the so-called film grain clearly. Figure G shows an enlargement of a photograph of a plain grey card. Under a powerful electron microscope, in Figure H, we can see the individual crystals on the photographic film. None of the methods we have seen so far allow for the automatic conversion of photographic content to a printable form such as a plate which might be wanted for a daily newspaper. We have a grey tone image, in the form of a photographic negative. Our printing process, however, allows only black and white, so we wish to automatically convert the grey tones to a series of regularly spaced dots whose diameter reflects the level of grey. Here is our gradient, followed by its so-called halftone: #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 157 Context: # Chapter 10: Words to Paragraphs The finished paragraphs of type are arranged in a **galley**. This will be used to make prints of the page (or pages – two or four may be printed from one galley, then folded and cut). You can imagine how long it takes to make up the galleys for a book, and how much time is required to justify each line by inserting exactly the right spaces and hyphenating by hand. Mistakes found after test prints can be very costly to fix, since they necessitate taking apart the galleys. #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 22 Context: # Chapter 1. Putting Marks on Paper & & & On the left is an idealised high-resolution shape. In the middle, just black and white at a lower resolution. On the right, prepared for display on a screen supporting grey as well as black and white, at the same lower resolution. This use of grey is known as **antialiasing**, since the jagged edges in low-resolution lines are known as **aliasing**. This term originated in the field of signal processing and is used to describe problems stemming from low-resolution versions of high-resolution signals. Here is a photograph, taken under a microscope, of such an antialiased line on a modern computer screen:  The left image is magnified 20×; the right image 400×. The rectangular shapes you can see in the images are the separated Red, Green, and Blue sub-pixels, which a monitor uses to build up all the different colours and greys it may need (the monitor makes a picture by emitting light and Red, Green, and Blue are the primary colours of light). What might a reasonable minimum resolution be? To simplify, let’s return to the scenario where we only have black and white dots—no antialiasing. The resolution required to make the page look smooth depends on the distance at which the typical viewer sees it. For a computer screen, this might be twenty inches. For a smartphone, eight inches. For a billboard, twenty or fifty feet (if you have ever walked right up to a billboard and looked at the printing, do so—it is surprisingly coarse). The limit of the human optical system’s ability to distinguish the colour of adjacent dots is crucial. #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 190 Context: 176TemplatesProblem2.1 #################### File: 15-MB-docx-file-download.pdf Page: 4 Context: Praesent semper molestie dolor eget bibendum. Pellentesque ut nisi eros laoreet suscipit. Mauris lacinia rhoncus elit. Nullam id metus et eros rhoncus la blandit. Pellentesque massa augue, mollis eu dui eget, egestas ornare velit. Morbi ultrices nisl a lacinia commodo. Pellentesque faucibus purus ante, id vehicula arcu tincidunt ac. Orci varius natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. ## Ut libero massa Auctor et tortor ut, lacinia semper massa. Etiam a tortor turpis. Donec bibendum ipsum in laoreet euismod. Donec nec lectus purus. Praesent a porttitor lectus. Etiam cursus, ipsum ut maximus tincidunt, risus velit mattis felis, sed sodales odio leo volutpat sapien. Etiam a faucibus nunc. Ut magna elit, cursus a posuere ac, lobortis in orci. ## Nulla facilisi Sed sollicitudin dictum metus, vel dapibus magna accumsan ut. Nulla in laoreet velit. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Morbi sit amet malesuada leo, non tincidunt augue. Curabitur venenatis bibendum rutrum. Vestibulum porta purus vel mattis dictum. Nam ac dictum justo. Mauris commodo, orci ut bibendum iaculis, elit nisi euismod leo, nec bibendum lectus lorem in purus. Mauris nec dictum mi, at dictum augue. Integer imperdiet sed nisi quis fermentum. ## Nullam libero justo Accumsan eget est, a rhoncus orci ante ligula. Mauris bibendum tempus consequat. Curabitur semper quis leo nec viverra. Pellentesque mollis placerat tincidunt. Etiam id ### Boundary Waters Trip - Day 1 - Day 2 - Day 3 - Day 4 - Day 5 - End Point Nisl a nisl elementum condimentum. Nunc non eleifend turpis, pulvinar eleifend purus. Cras sodales augue et libero consectetur iaculis in elit. In sed lectus rhoncus, sagittis sem eget, dignissim orci. Phasellus euismod augue nec sapien aliquam interdum. Sed iaculis in lacus eget tincidunt. Sed molestie, enim nec lobortis sagittis, tortor neque malesuada risus, nec molestie massa tortor non leo. Donec gravida vestibulum mauris, sed faucibus tortor consectetur id. Aliquam sit amet nulla ut orci porta venenatis. Vivamus posuere, metus pulvinar aliquam ullamcorper, dolor dui hendrerit metus, eget fermentum urna diam at nisl. #################### File: 15-MB-docx-file-download.pdf Page: 14 Context: I'm unable to assist with the content you provided as it includes an image that I cannot access. If you provide the text you'd like me to help with in Markdown format, I'd be happy to assist in correcting any visible mistakes or formatting issues. #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 7 Context: PrefaceItcanbetremendouslydifficultforanoutsidertounderstandwhycomputerscientistsareinterestedinComputerScience.Itiseasytoseethesenseofwonderoftheastrophysicist,oroftheevolutionarybiologistorzoologist.Wedon’tknowtoomuchaboutthemathe-matician,butweareinaweanyway.ButComputerScience?Well,wesupposeitmusthavetodowithcomputers,atleast.“Com-puterscienceisnomoreaboutcomputersthanastronomyisabouttelescopes”,thegreatDutchcomputerscientistEdsgerDijkstra(1930–2002),wrote.Thatistosay,thecomputerisourtoolforex-ploringthissubjectandforbuildingthingsinitsworld,butitisnottheworlditself.Thisbookmakesnoattemptatcompletenesswhatever.Itis,asthesubtitlesuggests,asetoflittlesketchesoftheuseofcomputersciencetoaddresstheproblemsofbookproduction.Bylookingfromdifferentanglesatinterestingchallengesandprettysolutions,wehopetogainsomeinsightintotheessenceofthething.Ihopethat,bytheend,youwillhavesomeunderstandingofwhythesethingsinterestcomputerscientistsand,perhaps,youwillfindthatsomeoftheminterestyou.vii #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 158 Context: # Chapter 10: Words to Paragraphs A galley, ready for printing:  Eventually, machines were developed to automatically place the pieces of type based on what was typed on a keyboard and to automatically justify each line. Such mechanical systems were in common use until the advent of so-called phototypesetting. This involved building an image by shining light through a series of stencils onto photosensitive paper, then photographing it. Computer typesetting supplanted both in the late twentieth century. #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 111 Context: # Chapter 8 ## Grey Areas With only black ink and white paper, we can draw both beautiful letters and good line drawings, such as the diagrams of Bézier curves from Chapter 2. But what about reproducing photographs? How can we create the intermediate grey tones? Consider the following two images: a photograph of a camel and a rather higher-resolution picture of a smooth gradient between black and white:   We shall use these pictures to compare the different methods of reproduction we discuss. From looking at the page (at least if you are reading this book in physical form rather than on a computer). #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 24 Context: 10Chapter1.PuttingMarksonPaperNow,wecanproceedtodesignamethodtofilltheshape.Foreachrowoftheimage,webeginontheleft,andproceedrightwardpixel-by-pixel.Ifweencounterablackdot,weremember,andenterfillingmode.Infillingmode,wefilleverydotblack,untilwehitanotherdotwhichwasalreadyblack–thenweleavefillingmode.Seeinganotheralready-blackdotputsusbackintofillingmode,andsoon.Intheimageabove,twolineshavebeenhighlighted.Inthefirst,weentertheshapeonceatthesideoftheroof,fillacross,andthenexititattherighthandsideoftheroof.Inthesecond,wefillasection,exittheshapewhenwehitthedoorframe,enteritagainattheotherdoorframe–fillingagain–andfinallyexitit.Ifwefollowthisprocedureforthewholeimage,thehouseisfilledasexpected.Theimageontheleftshowsthenewdotsingrey;thatontherightthefinalimage.Noticethatthewindowsanddoordidnotcauseaproblemforourmethod.Wehavenowlookedattheverybasicsofhowtoconvertde-scriptionsofshapesintopatternsofdotssuitableforaprinterorscreen.Inthenextchapter,wewillconsiderthemorecomplicated #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 21 Context: # Chapter 1. Putting Marks on Paper ## 7 Each column. For the line at exactly 45°, the two methods (row and column) produce the same result. Here is an illustration of the sorts of patterns of dots we see for lines of various slopes using this improved procedure:  This image is 100 dots tall and wide. The results are not terribly good, for two reasons. First, at low resolutions, the individual dots are clearly visible. Moreover, the density of the lines varies. A horizontal or vertical line of length 100 will have 100 dots over its length, but the 45° line has 100 dots over a length of about 141 (the diagonal of a square with sides of length 100 is √2 × 100), and so its density of dots is lower, and it appears less dark. When we are using a screen, rather than paper, to display our line, we can take advantage of the ability to use more than just black and white. And so, we can use varying shades of grey: dots which are right on the line are very dark grey, dots which are just close are lighter grey. Here is a line drawn in this manner, at three scales:  We can see that the line is smoother than would otherwise be the case. If you are reading this book on an electronic device, you may be able to see this effect on the text or images with a magnifying glass. Here is another example, with a more complex, filled shape, which might be used to represent an ampersand character:  #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 96 Context: 82Chapter7.DoingSumsNotethatforthistowork,wehavetoparenthesiseevenexpressionswheretheparenthesescannotaffecttheresult,forexample1+(2+(3+4)).Itcanbedifficultforhumanstoreadsuchover-parenthesisedex-pressions(whichiswhymathematiciansusetheminimumnumberofparenthesesandrelyonasetofad-hocrulesfordisambiguation–theinsistenceonexplicitprecisenesscanactuallybeantitheticaltodoingmathematics).Forcomputers,however,thisrepresentationisideal.Wecanseethestructureoftheseexpressionsmoreclearlybydrawingthemlikethis:+×321isthesameas1+(2×3)Thesearecalledtrees,becausetheyhaveabranchingstructure.Unlikerealtrees,wedrawthemupside-down,withtherootatthetop.Wecanshowthestepsofevaluation,justasbefore,withouttheneedforanyparentheses:+×321=⇒+61=⇒7Infact,thisistherepresentationacomputerwoulduseinter-nally(notliteraldrawings,ofcourse,butastructureofthisforminitsmemory).Whenwetypeinacomputerprogramusingthekeyboard,wemightwrite1+2*3.(Thereisno×keyonthekeyboard.)Itwillbeconvertedintotreeformandcanthenbeevaluatedautomatically,andquickly,bythecomputer.Whenwewriteinstructionsforcomputers,wewantasinglesetofinstructionstoworkforanygiveninput.Todothis,wewriteourexpressions–justlikeinmaths–tousequantitieslikexandyand #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 79 Context: Chapter6SavingSpaceAscomputersgeteverfaster,weaskevermoreofthem:ahigher-resolutionfilmstreamedinrealtime,afasterdownload,orthesameexperienceonamobiledeviceoveraslowconnectionaswehaveathomeorintheofficeoverafastone.Whenwetalkofefficiency,weareconcernedwiththetimetakentodoatask,thespacerequiredtostoredata,andknock-oneffectssuchashowoftenwehavetochargeourdevice’sbattery.Andsowecannotsimplysay“thingsaregettingfasterallthetime:weneednotworryaboutefficiency.”Animportanttoolforreducingthespaceinformationtakesup(andso,increasingthespeedwithwhichitcanbemovedaround)iscompression.Theideaistoprocesstheinformationinsuchaswaythatitbecomessmaller,butalsosothatitmaybedecompressed–thatistosay,theprocessmustbereversible.Imaginewewanttosendacoffeeorder.Insteadofwriting“Fourespressos,twodoubleespressos,acappuccino,andtwolattes”,wemightwrite“4E2DC2L”.Thisrelies,ofcourse,onthepersontowhomwearesendingtheorderknowinghowtodecompressit.Theinstructionsfordecompressingmightbelongerthanthemessageitself,butifwearesendingsimilarmessageseachday,weneedonlysharetheinstructionsonce.Wehavereducedthemessagefrom67charactersto7,makingitalmosttentimessmaller.Thissortofcompressionhappensroutinely,anditisreallyjustamatterofchoosingabetterrepresentationforstoringaparticularkindofinformation.Ittendstobemoresuccessfulthemoreuniformthedatais.Canwecomeupwithacompressionmethodwhichworksforanydata?Ifnot,whataboutonewhichworkswell65 #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 5 Context: ContentsPrefacev1PuttingMarksonPaper12LetterForms153StoringWords274LookingandFinding415TypingitIn536SavingSpace657DoingSums818GreyAreas979OurTypeface12310WordstoParagraphs135Solutions147FurtherReading169Templates173Colophon181Index183v #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 193 Context: Templates179Problem8.3 #################### File: 15-MB-docx-file-download.pdf Page: 1 Context: # Boundary Waters Trip ![Boundary Waters Trip Map](https://via.placeholder.com/500x300.png?text=Boundary+Waters+Trip+"Day+1+to+Day+5+Routes+Map") Curabitur bibendum ante urna, sed blandit libero egestas id. Pellentesque rhoncus elit in lacus ultricies fringilla. Nam ac metus eu turpis mattis rhoncus. Mauris mattis sem ex, facilisis molestie sapien luctus non. Vestibulum tincidunt urna at odio suscipit, vel congue felis cursus. Etiam tellus magna, egestas ac suscipit in, laoreet quis felis. Proin non orci id dui tincidunt egestas. Vestibulum eleifend, ligula a scelerisque vehicula, risus justo ultricies ligula, et interdum lorem eu eget eu. Duis dignissim lacus vitae velit laoreet, vitae placaret velit aliquet. Etiam eget mollis nulla, ac vehicula mi. Etiam non sollicitudin velit, imperdiet commodo mi. Fusce quis tellus tellus. Donec dictum eulismod risus non tempus. Duis quis pellentesque nunc. Praesent elementum condimentum mollis. Phasellus dapibus quam a hendrerit placerat. Sed ultricies blandit nulla sed sodales. Nunc quis volutpat eros. Etiam bibendum eu tellus consequat blandit. Curabitur lacinia cursus diam sed pharetra. Proin molestie tristique mauris eu aliquam. Donec purus odio, molestie id suscipit sit amet, porttitor in erat. Vestibulum eu tellus vel lobortis porta nec elit tellus. Quisque pretium blandit dignissim. Proin eu metus convallis sapien efficitur mollis. Nunc luctus ex in nunc ornare, nec blandit orci faucibus. Aenean bibendum mi vel neque euismod hendrerit. Vestibulum ac pharetra magna. Ut rutrum, orci at blandit faucibus, justo mauris aliquet mauris, ut tempor lectus risus at ligula. Duis non tincidunt purus. Nam quis aliquam risus. Donec mattis convallis tempus. Fusce aliquam aliquet eros, nec rutrum lectus pretium a. Praesent blandit justo a mi dignissim placerat. Ut ullamcorper elit eget diam maximus luctus. In bibendum in massa eget facilisis. In iaculis lectus nec neque vehicula, ac molestie ante ornare. Sed sit amet sem mollis, egestas justo ac, rhoncus nunc. In in aliquam ante, non imperdiet ante. Mauris in sapien eu quam hendrerit mollis. Proin feugiat dignissim nisi, sed tincidunt ante aliquam et. Integer finibus est augue a tempus. Nullam facilisis quis nisl sit amet iaculis. Integer hendrerit metus in faucibus aliquet. Donec fermentum, lacus lobortis pulvinar vestibulum, felis ipsum auctor mi, ac pulvinar lacus magna. #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 102 Context: 88Chapter7.DoingSumsIfyisgreaterthan0,ontheotherhand,wewanttocalculatextimesxy−1:powerxy=ify=0then1elsex×powerx(y−1)So,wecannowcalculate25,showingjusttheimportantsteps:power25=⇒2×power24=⇒2×(2×power23)=⇒2×(2×(2×power22))=⇒2×(2×(2×(2×power21)))=⇒2×(2×(2×(2×(2×power20))))=⇒2×(2×(2×(2×(2×1))))=⇒32Wehavelookedatnumberslike2and32,andthetruthvaluestrueandfalse,butinterestingprogramsoftenhavetooperateonmorecomplicatedstructures.Onesuchisalist,whichwewritewithsquarebracketsandcommas,likethis:[1,5,4].Alistisanorderedcollectionofothervalues.Thatistosay,thelists[1,5,4]and[5,4,1]aredifferent,eventhoughtheycontainthesamevalues.Thereisanemptylist[]whichcontainsnoitems.Thefirstelementofalistiscalledthehead,andthereisabuilt-infunctiontogetatit:head[1,5,4]=⇒1Therestoftheelementsarecollectivelyreferredtoasthetail,andagainthereisabuilt-infunctiontoretrieveit:tail[1,5,4]=⇒[5,4]Theemptylist[]hasneitheraheadnoratail.Weneedjustonemorethingforourexampleprograms,andthatisthe•operatorwhichstickstwoliststogether:[1,5,4]•[2,3]=⇒[1,5,4,2,3] #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 18 Context: # Chapter 1. Putting Marks on Paper The upper row shows high-resolution printing of lettering on coated paper, such as might be used for a glossy pamphlet, under a microscope at 20x magnification, and the same at 400x magnification. The lower row is standard text of the London Times printed on newsprint at 20x magnification and the same at 400x magnification. The home or office laser printer works by using a laser to prepare a roller in such a way that a powder will adhere only to areas where the laser has not been shone. The powder (called toner) is then transferred from the roller to paper, and bonded to it by heat. The particles of toner behave differently from ink: - On the left is a word printed in 1pt, 2pt, 4pt, 6pt, and 8pt text under a microscope, with magnification at 20x. - On the right, the particles of toner are shown. #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 78 Context: # Chapter 5. Typing it In Again, we choose the tone. Contextual information, such as the previous character, is used to disambiguate the two-character sequence and, in this case, the most common possibility is correct: ## 應去彆 ## 樱桃 Different systems are popular in each part of Asia and in each generation, and depend upon the device in use. Indeed, one person may use a particular system on their computer and entirely another on their mobile phone, which has even less space for keys (real or virtual). We have seen how English and the world’s many other languages might be typed into the computer. There have been many attempts to replace the keyboard for text input, such as voice recognition, which have made some inroads in automotive and niche applications, but for general purpose computing, the keyboard, real or virtual, is still king. #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 115 Context: # Chapter 8. Grey Areas  is similar to a child cutting a potato to make a stamp – the wood is removed in areas where the artist does not want ink, and then ink is applied to the raised portions. Figure A shows a woodblock print *Der Formschnider* (The Blockcutter) from the *Panopticon omnia utilitarian mechanicarum* (Book of Trades), published in Germany in 1568. The detail achievable depends on the closeness of the grain of the wood, the properties of the ink and paper, and the permeability of the wood to ink. Attempts to produce areas which appear grey by using hatching or other patterns are likely to be either too coarse to be convincing, or they result in a solid inked area due to ink spreading across the surface of the block or along the fibres of the paper. The term *intaglio* (in-tah-lee-o), from the Italian *intagliare* – to engrave – refers to a group of techniques in which a metal plate has material removed manually, is rubbed with viscous ink all over, has the excess removed carefully with a cloth, and is then pressed onto a dampened piece of paper. The ink remains only in the lines engraved in the plate, and is transferred to the paper by the pressure of the press. Thus, the removal of material is normally done in the opposite sense to that in the woodblock process: we engrave where we want ink to be present, not where we want it to be absent. #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 128 Context: # Chapter 8. Grey Areas   For colour images, several halftone screens are used, one for each of the primary printing colours used in the particular printing technology – often cyan, magenta, yellow, and black. The halftones are at different angles, so that the colours do not interfere with one another and the ink is more evenly distributed. Here is part of a glossy colour leaflet at 20x and 400x:   When we are producing a result for a type of device that has reasonably sharp or predictable dots (such as a computer monitor) and none of the vagaries of ink-flow, we can choose a more appropriate ordered dither, free of the need to build a spot as such, leading to the appearance of a higher resolution. Black and white computer displays are rather rare these days but were common in the past. Consider the following table and pattern for the 2x2 case: | | 2 | 3 | |---|---|---| | 4 | 1 | | - A pixel representation: - [ ] [ ] - [ ] [X] #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 91 Context: # Chapter 6. Saving Space  |  :--: | :--:  |  *Figure C*  |  :--: | :--:  |  *Figure D* #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 25 Context: Chapter1.PuttingMarksonPaper11shapesneededtodrawgoodtypefaces,whichconsistnotonlyofstraightlines,butalsocurves. #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 132 Context: ``` # Chapter 8. Grey Areas  Our small-dot ordered dither patterns, suitable for on-screen use where pixels are clearly defined (unlike ink on paper), are not too bad. They do the job of creating the impression of grey shades where only black and white exist. However, the regular patterns of dots can be distracting; we see those patterns instead of the image, since our eyes are drawn to regular features. The technique of error diffusion leads to a better result than ordered dithering, with fewer distracting patterns. This method was invented in 1976 by Robert W. Floyd and his student Louis Steinberg at Stanford University. Say that we have an image made up of greys numbered between 0% (ink (white) and 100% ink (black) like the one in this diagram—unavoidably, we shall have to use a somewhat small example: | 50 | 20 | 70 | |----|----|----| | 40 | 30 | 70 | | 50 | 40 | 90 | We proceed pixel by pixel, starting at the top left, dealing with a row of pixels in order and then moving on to the next row until we have looked at the whole image. For each pixel, we first decide whether to paint it black or white in the final image. If it is 50 percent or more black, we make that pixel black; if it is less than 50 percent, we make it white. We write this value to the final image. Now, we consider the error inherent in that choice—that is to say, how much too white or too black we were forced to make the pixel due to only having fully white and fully black available. For example, on the first pixel, we would choose to place a 100% black pixel, and the original value was 50%, so we were forced to make it 50% too black. We redistribute this error to some of the surrounding pixels. ``` #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 180 Context: 166SolutionsChapter91Palatino2AVERSION3ConjectureChapter101hy-phen-a-tion2fund-raising3a-rith-me-tic(thenoun)4ar-ith-me-tic(theadjective)5dem-on-stra-tion #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 142 Context: 128Chapter9.OurTypefaceThediagramshowsvariousalternativecharactersfor“d”and“g”intheZapfinotypeface.Youcanseethatsomesuitthewordmorethanothers.Inparticular,inthebottom-rightexample,theinitial“d”clashesawfullywiththenextletter.Beforecomputers,whentypewassetmanuallyusinglittlemetalpiecesarrangedintorows,smearedinink,andpressedontopaper,itwasnaturalforatypefacetohaveslightlydifferentglyphdesignsforeachsize.Aheadlinewouldhaveasubtlydifferentcharacterdesigntonormalsizedtext,andagaindifferenttothesortoftinytextusedforfootnotes.Partofthisisduetotheessentialopticalcharacteristicsofsmallshapes:itiseasiertoreadasmalltypefaceifithasproportionallywidercharactersthanitsnormalsize,forexample.Partofithastodowiththephysicalcharacteristicsoftheinkandpaper:inkspreads,andthewayitspreadsleadstothesamemetalshapeshowingdifferentlyatdifferentsizes.Whendesigningatypefacebycomputer,however,itistemptingtotakeashortcut:designthetypefaceonce,andthenautomaticallyscaleittowhateversizeisneededbysimplearithmeticonitscoordi-nates.Now,wehaveanysizeavailable,anddesigningthetypefaceischeaper.Thisshortcutwasnotavailabletothemetaltypeman-ufacturer.However,manygoodmoderncomputertypefacesstillhavemultipleso-calledopticalsizes.Theymayhaveseparateshapesfor5pt,8pt,10pt,12pt,and16pt,forexample.Wecanusethecom-puterscalingmethodinbetweensizes–toobtain11pt,forexample.FigureAontheoppositepageshowsaphraseprintedintheLatinModerntypeface,atfivedifferentsizes.Below,thesamephrasehasbeenrepeated,butscaleduptoshowthedifferencesclearly.WehavenotyetlookedattheotherthreefacesofthePalatinotypeface:theBold,theItalic,andtheBoldItalic.Aboldtypefaceisonewhichisthicker,usingmoreink.TheItalichasadifferent,slopingshape.Bothareusedforemphasis.YoucanseeBoldandItalicusedinvariousplacesinthisbook,butwedon’tuseBoldItalic.Thevariousshapesaredesignedtoworkcomfortablytogether.ShapeShapeShapeShape #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 152 Context: 138Chapter10.WordstoParagraphsatanypointtoaddingorremovingspacebetweenwords.Theparagraphontherightfollowsusualtypesettingandhyphenationrules,preferringtheaddingofspacetohyphenation.Onemorning,whenGregorSamsawokefromtrouble-ddreams,hefoundhims-elftransformedinhisbedintoahorriblevermin.Helayonhisarmour-likeback,andifheliftedhisheadalittlehecouldseehisbrow-nbelly,slightlydomedanddividedbyarchesintostiffsections.Onemorning,whenGre-gorSamsawokefromtrou-bleddreams,hefoundhimselftransformedinhisbedintoahorriblevermin.Helayonhisarmour-likeback,andifheliftedhisheadalittlehecouldseehisbrownbelly,slightlydomedanddividedbyarchesintostiffsections.Theseareveryuglyhyphenations,however:wehave“trouble-d”,“hims-elf”,and“brow-n”.Everywordhasplaceswhicharebetterorworseforhyphenation.Wewouldprefer“trou-bled”and“him-self”.Ideally“brown”shouldnotbehyphenatedatall.Somewordsmustbehyphenateddifferentlydependingoncontext:“rec-ord”forthenoun,“re-cord”fortheverb,forexample.Inaddition,authoritiesonhyphenation(suchasdictionarieswhichincludehyphenationinformation)donotalwaysagree:Websterhas“in-de-pen-dent”and“tri-bune”,AmericanHeritagehas“in-de-pend-ent”and“trib-une”.Therearewordswhichshouldneverbehyphenated.Forexample,thereisnoreallygoodplacetobreak“squirm”.Therearetwomethodsforsolvingthisproblemautomaticallyasthecomputertypesetsthelines:adictionary-basedsystemsimplystoresanentirewordlistwiththehyphenationpointsforeachword.Thisensuresperfecthyphenationforknownwords,butdoesnothelpusatallwhenanewwordisencountered(asitoftenisinscientificortechnicalpublications,orifweneedtohyphenateapropernoun,suchasathenameofapersonorcity).Thealternativeisarule-basedsystem,whichfollowsasetofrulesaboutwhataretypicallygoodandbadbreaks.Forexample“abreakisalwaysallowableafter“q”iffollowedbyavowel”or“ahyphenisfinebefore-ness”or“ahyphenisgoodbetween“x”and“p”inallcircumstances”.Wemayalsohaveinhibitingrulessuchas“neverbreakb-ly”.Somepatternsmayonlyapplyatthebeginningorendofaword,othersapplyanywhere.Infact,theserulescanbeder #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 192 Context: 178TemplatesProblem8.2 #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 124 Context: # Chapter 8: Grey Areas ## Figure J: Small, medium, and large halftone dots.    - Small halftone dots: Represents the lightest parts of the image. - Medium halftone dots: Represents the mid-tones. - Large halftone dots: Represents the darkest parts of the image. #################### File: 15-MB-docx-file-download.pdf Page: 9 Context: Donec posuere, elit sit amet sodales sollicitudin, lacus eros mattis libero, non hendrerit lacus lacus vulputate purus. Vestibulum eget diam quis nisl interdum placerat ut in lacus. Vestibulum rutrum dui ipsum, in elementum ipsum semper id. Etiam lacinia tellus sit amet nisi finibus, vel ornare elit vestibulum. Sed accumsan volutpat pellentesque. Donec vestibulum, felis quis vestibulum commodo, elit ligula blandit augue, et iaculis nulla velit nec nunc. Phasellus magna dui, interdum vitae nulla eget, ornare pharetra leo. Quisque ultrices posuere lorem id ultrices. Phasellus eget bibendum eros. Maecenas porttitor dictum justo, et euismod metus scelerisque eget. Vivamus et mi tincidunt, pretium augue sit amet, porta libero. Morbi luctus eu purus quis consectetur. Aliquam elementum sapien ipsum, 0123456Category 1Category 2Category 3Category 4Series 1Series 2Series 3 #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 143 Context: Chapter9.OurTypeface129(cid:80)(cid:84)(cid:105)(cid:66)(cid:43)(cid:28)(cid:72)(cid:54)(cid:81)(cid:77)(cid:105)(cid:97)(cid:66)(cid:120)(cid:50)(cid:98)(cid:80)(cid:84)(cid:105)(cid:66)(cid:43)(cid:28)(cid:72)(cid:54)(cid:81)(cid:77)(cid:105)(cid:97)(cid:66)(cid:120)(cid:50)(cid:98)(cid:80)(cid:84)(cid:105)(cid:66)(cid:43)(cid:28)(cid:72)(cid:54)(cid:81)(cid:77)(cid:105)(cid:97)(cid:66)(cid:120)(cid:50)(cid:98)(cid:80)(cid:84)(cid:105)(cid:66)(cid:43)(cid:28)(cid:72)(cid:54)(cid:81)(cid:77)(cid:105)(cid:97)(cid:66)(cid:120)(cid:50)(cid:98)(cid:80)(cid:84)(cid:105)(cid:66)(cid:43)(cid:28)(cid:72)(cid:54)(cid:81)(cid:77)(cid:105)(cid:97)(cid:66)(cid:120)(cid:50)(cid:98)(cid:80)(cid:84)(cid:105)(cid:66)(cid:43)(cid:28)(cid:72)(cid:54)(cid:81)(cid:77)(cid:105)(cid:97)(cid:66)(cid:120)(cid:50)(cid:98)(cid:80)(cid:84)(cid:105)(cid:66)(cid:43)(cid:28)(cid:72)(cid:54)(cid:81)(cid:77)(cid:105)(cid:97)(cid:66)(cid:120)(cid:50)(cid:98)(cid:80)(cid:84)(cid:105)(cid:66)(cid:43)(cid:28)(cid:72)(cid:54)(cid:81)(cid:77)(cid:105)(cid:97)(cid:66)(cid:120)(cid:50)(cid:98)(cid:80)(cid:84)(cid:105)(cid:66)(cid:43)(cid:28)(cid:72)(cid:54)(cid:81)(cid:77)(cid:105)(cid:97)(cid:66)(cid:120)(cid:50)(cid:98)(cid:80)(cid:84)(cid:105)(cid:66)(cid:43)(cid:28)(cid:72)(cid:54)(cid:81)(cid:77)(cid:105)(cid:97)(cid:66)(cid:120)(cid:50)(cid:98)(cid:82)FigureAYoucanseethattheItalichasanentirelydifferentshapefromtheRoman.ThisisusualforseriftypefacessuchasPalatino.(Serifsarethelittlepiecesattachedtotheendofeachstrokeoftheletter.)However,forasansseriftypeface(onewithoutserifs),itissufficienttosimplyslanttheshapesbyfifteendegreesorso.Thiscanbedoneautomaticallybythecomputer,sothetypefacedesignerneedonlydesigntheRomanshapes.Unfortunately,automaticallyproducingaBoldfacefromaRomanoneisrathermoredifficult,soitisusuallydonemanually,albeitwithhelpfromcomputertools.Thisdiagramshowsanautomatically-generatedobliquefaceandaseparately-designeditalicface:Oblique ItalicOblique Italic #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 127 Context: # Chapter 8. Grey Areas  As the tone moves from white to black, the spot grows gradually. If you imagine the patterns tiled repeatedly across the page, you can see that the white sections left in the corners as the black spot grows themselves form white spots. Thus, we have a smooth transition. Here is the result of dithering these patterns for the camel and the gradient:  --- Prop this book up against a wall, retreat to the other side of the room (or perhaps halfway), and see which looks more camel-like. What about at normal reading distance? Such halftone patterns are used in most modern printing. Here are microscopic pictures of the camel as it is printed at the head of this chapter, at 20x and 400x magnification:   #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 183 Context: FurtherReadingTherefollowsalistofinterestingbooksforeachchapter.Somearecloselyrelatedtothechaptercontents,sometangentially.Thelevelofexpertiserequiredtounderstandeachofthemvariesquiteabit,butdonotbeafraidtoreadbooksyoudonotunderstandallof,especiallyifyoucanobtainorborrowthematlittlecost.Chapter1ComputerGraphics:PrinciplesandPracticeJamesD.Foley,AndriesvanDam,StevenK.Fiener,andJohnF.Hughes.PublishedbyAddisonWesley(secondedition,1995).ISBN0201848406.ContemporaryNewspaperDesign:ShapingtheNewsintheDigitalAge–Typography&ImageonModernNewsprintJohnD.BerryandRogerBlack.PublishedbyMarkBatty(2007).ISBN0972424032.Chapter2ABookofCurvesE.H.Lockwood.PublishedbyCambridgeUniver-sityPress(1961).ISBN0521044448.FiftyTypefacesThatChangedtheWorld:DesignMuseumFiftyJohnL.Waters.PublishedbyConran(2013).ISBN184091629X.ThinkingwithType:ACriticalGuideforDesigners,Writers,Editors,andStudentsEllenLupton.PublishedbyPrincetonArchitecturalPress(secondedition,2010).ISBN1568989695.169 #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 191 Context: Templates177Problem8.1 #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 52 Context: ```markdown # Chapter 3. Storing Words ## Braille Patterns The top section contains all those combinations using the top six dots only. (There were originally only six dots in Braille.) All the others then follow, for a total of 256. The patterns are not assigned particular letters, because these vary for each language: a pattern might represent the letter A in Western languages and something entirely different in Japanese or Vietnamese. Empty circles are used in most Braille typefaces so that, in patterns with only a few black dots, the empty circles can be felt with the finger to help distinguish between different characters. This is particularly useful when dealing with 8-dot patterns. | | 230 | 231 | 232 | 236 | 237 | 238 | 239 | 240 | 241 | 242 | 246 | 247 | 248 | 250 | 251 | 252 | |---|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----| | 0 | | | | | | | | | | | | | | | | | | 1 | | | | | | | | | | | | | | | | | | 2 | | | | | | | | | | | | | | | | | | 3 | | | | | | | | | | | | | | | | | | 4 | | | | | | | | | | | | | | | | | | 5 | | | | | | | | | | | | | | | | | | 6 | | | | | | | | | | | | | | | | | | 7 | | | | | | | | | | | | | | | | | | 8 | | | | | | | | | | | | | | | | | | 9 | | | | | | | | | | | | | | | | | | A | | | | | | | | | | | | | | | | | | B | | | | | | | | | | | | | | | | | | C | | | | | | | | | | | | | | | | | | D | | | | | | | | | | | | | | | | | | E | | | | | | | | | | | | | | | | | | F | | | | | | | | | | | | | | | | | | G | | | | | | | | | | | | | | | | | | H | | | | | | | | | | | | | | | | | | I | | | | | | | | | | | | | | | | | | J | | | | | | | | | | | | | | | | | | K | | | | | | | | | | | | | | | | | | L | | | | | | | | | | | | | | | | | | M | | | | | | | | | | | | | | | | | | N | | | | | | | | | | | | | | | | | | O | | | | | | | | | | | | | | | | | | P | | | | | | | | | | | | | | | | | ``` #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 134 Context: # Chapter 8. Grey Areas ``` 100 | 0 | 100 --- |---|--- 0 | 100 | 0 100 | 0 | 100 ``` Here is our camel picture and gradient processed with the algorithm described above.  You can see that there appear to be much finer gradations of grey and that, whilst the eye can discern some patterns in the flat shaded areas, they are much less distracting than in the case of the ordered dither. Overall, a much more pleasing result. The gradient is much finer too, especially when viewed from a distance. There are several newer variations on this procedure, using more complicated diffusion of errors. #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 108 Context: 94Chapter7.DoingSumsProblemsSolutionsonpage159.1.Evaluatethefollowingsimpleexpressions,followingnormalmathematicalrulesandaddingparentheseswhereneeded.Showeachevaluationinbothtreeandtextualform.a)1+1+1b)2×2×2c)2×3+42.Inanenvironmentinwhichx=4,y=5,z=100,evaluatethefollowingexpressions:a)x×x×yb)z×y+zc)z×z3.Considerthefollowingfunction,whichhastwoinputs–xandy:fxy=x×y×xEvaluatethefollowingexpressions:a)f45b)f(f45)5c)f(f45)(f54)4.Recallthetruthvaluestrueandfalse,andtheif...then...elseconstruction.Evaluatethefollowingexpressions:a)f54=f45b)if1=2then3else4c)if(if1=2thenfalseelsetrue)then3else45.Evaluatethefollowinglistexpressions:a)head[2,3,4]b)tail[2]c)[head[2,3,4]]•[2,3,4] #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 156 Context: # Chapter 10. Words to Paragraphs We have shown the river with a line. Notice that the word "fermentum" appearing in almost the same place on two successive lines is also distracting. The problem is difficult to deal with automatically, and the text may have to be edited to fix it. The microtypographical techniques discussed above can help a little—since there are fewer widened spaces between words, the rivers will be narrower and less noticeable. You may wonder how type was set before computers. In much the same way, it turns out, but with many more manual steps and a lot of little pieces of metal. Here is one such piece, for the character “n” at a particular size, in a particular typeface: | Character | Description | |-----------|----------------------| | n | Body Shank | | ---- | Groove | | ---- | Foot | | ---- | Ratio | | ---- | Width | These are picked from a tray of boxes, by hand, and placed into rows in a composing stick, each row separated by little metal spaces, each row spaced by a metal strip (the leading). You can imagine that many many copies of these little metal pieces were required for each typeface and size, so it was an expensive business. Because it would eventually be used for printing by being inked and stamped or rolled on paper, the type is mirrored, and hard to read, and one must be careful not to mix up “p” and “q”, or “b” and “d”. (This is one possible origin of the phrase "mind your P's and Q's.") This painstaking process is shown on the opposite page. #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 177 Context: # Chapter 8 1 | | | | | |---|---|---|---| | | ▓ | | | | ▓ | ▓ | | | | ▓ | ▓ | ▓ | ▓ | | ▓ | ▓ | ▓ | | | | | ▓ | | | | | | ▓ | | | | | |   #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 20 Context: 6Chapter1.PuttingMarksonPaperchoosethedotwhosecentreisclosesttothelineineachcase:012345670123xyAdmittedly,thisdoesnotlookmuchlikealine.Butifwechooseahigherresolutionforalineofthesameslope,andsodrawmoreandsmallerdots,weseeabetterapproximation:0510150246810xyNow,youmaywonderwhywechosetodrawonedotineachcolumninsteadofonedotineachrow.Forexample,insteadofputtingonedotineachofthecolumnsfromcolumn1tocolumn6,wemightputonedotineachoftherowsfromrow1torow3,againchoosingtheoneinthatrownearesttheactualline.Forthisshallowline,doingsowouldleadtoamostunpleasantresult:012345670123xyIfthelineissteeperthan45°,theconverseistrue(drawitonpapertosee).So,wechoosetoputoneblackdotineachrowinsteadofineachcolumninthiscase.Horizontalandverticallinesaresimplyspecialcasesofthisgeneralmethod–fortheverticalcasewedrawonedotineachrow;forthehorizontalcaseonedotin #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 75 Context: # Chapter 5. Typing it In What of languages other than English? We can divide them into three categories. First, those which use the so-called Latin alphabet (that is the familiar ABC…), but which contain characters with accents, or one or two extra characters only. Typically, these can be typed on a standard keyboard, using either modifiers keys (holding down a key to make the next letter accented) or by using short sequences of keys (typing “’” followed by the “a” key for “ä”). The second category is those languages, such as Modern Greek, which do not use the Latin alphabet, but whose alphabet has only a few tens of characters. These can be dealt with by using the same keyboard, simply with different letters printed on it. The last category is for languages such as Chinese. There are many tens of thousands of characters, and it is impractical to build a keyboard that with that many keys, or to use one. Some system must be devised to allow all these characters to be typed on a limited number of keys. This is known as an **input system**. One such input system in use in China, Singapore, and Taiwan is **Pinyin**. It requires knowing the pronunciation of the word; westernized spellings of the syllables are then used to find the right character. We shall write the word 樱桃, which means cherry. In the Pinyin system, we type the western characters representing the sounds, and we are then invited to disambiguate amongst the possibilities, as the word is formed. The word for cherry sounds like “ying” followed by “tao”. First, we type “ying”: ``` ying ``` The computer displays a list of possibilities for the first character of our word. It does not yet know which syllable or syllables may follow. We choose the right one, and the computer replaces “ying” with the proper character. #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 17 Context: # Chapter 1. Putting Marks on Paper be reading this as a physical paperback book, printed and bound by very expensive equipment. You may be reading it as an electronic document (such as a PDF file) on your computer, tablet, or smartphone. Or, you may be reading it on some sort of special-purpose eBook reader. Each of these scenarios has different characteristics. Every page of the printed book is made up of hundreds of millions of little dots, each of which may be white (no ink) or black (ink). We cannot typically see the dots with the naked eye. The number of dots is known as the **resolution** (from the word "resolve"). A low resolution image is one where it is easy for the eye to resolve (that is, distinguish) the individual dots. A high-resolution image has dots so small and tightly packed that the naked eye cannot distinguish them. A high-resolution printer, such as the one printing the physical copy of this book, may have as many as 600 or 1200 dots per inch (dpi); that is to say, between 600 × 600 = 360,000 and 1200 × 1200 = 1,440,000 dots per square inch. The screen of a computer or tablet may only have 100 to 300 dpi, but it can display many shades of grey and colours. If the resolution is too low, we see blocky images. Here is a part of a capital letter A in black and white at 60 dpi, 30 dpi, and 15 dpi: ``` A ``` We have used square dots here, as may be used on a modern computer screen (we call them **pixels**, which is short for "picture elements"). For viewing a page on a typical computer viewer, we might have a book 2018 × 1536 = 5,193,728 dots on the whole screen, but they may be colours or greys, as well as black or white. When printing a book like this, we have many more dots, but only black ink. Let us say, for example, that we have a US Letter page (8.5 inches by 11 inches) and we are printing at a resolution of 1200 dpi. We have 1200 × 1200 = 1,440,000 dots per square inch, so we have 1200 × 8.5 × 11, or 134,640,000 dots on the page, each of which may be black or white. Here are some photographs, taken under a microscope, of lettering as it appears in high-quality printing, and on the next lower quality, cheaper newsprint used for the daily newspaper: #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 122 Context: # Chapter 8. Grey Areas You can see that the spacing of the dots is quite wide, and that they can be quite large: this is counterintuitive but deliberate. By making sure that the dots are properly separate, we make the image easily reproducible, even on cheap, porous newsprint. Perhaps 50 to 80 lines of dots per inch is sufficient. For higher-quality coated paper used in book production, we might be able to go as far as 150 lines per inch or ppi. Early methods of halftone production involved placing a device known as a halftone screen in front of photographic paper and projecting the original image through it with the use of a camera lens. The first halftone screens were made in about 1850 from a fine cloth gauze by the British scientist William Henry Fox Talbot (1800–1877). Later, they were commercially manufactured from glass engraved with a grid of lines. The effect of these, through optical effects, is to project a halftone image—a series of distinct dots of varying size—onto the photographic paper. This can then be used as the starting point for producing plates for printing. The image has successfully been reduced to only black and white through purely physical means. Figure 1 is one of the earliest halftone pictures in mass production: it shows Steinway Hall on East 14th Street in Manhattan, printed in the Daily Graphic on December 2nd 1873. This was the first method of printing a photograph direct from the negative with no manual intervention. Returning to Computer Science, we can simulate the halftone screen in software, to produce the appropriate dot pattern for printing. Consider the three versions of our camel figure: 1. The first one, with the smallest dots, seems to have the highest effective sharpness and visual resolution. 2. The middle image, when viewed at a distance, is in fact a closer representation of the original image. 3. The last one has yet more sizes of dots (and so, effective grey levels) but the resolution is now too coarse. We turn to our gradient for another look, printed in the same halftones as the camel pictures: #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 130 Context: # Chapter 8. Grey Areas | | | | | | |-----|-----|-----|-----|-----| | # | # | | # | # | | # | # | | # | # | | | | | | | | | | | | | This time, the results are rather better, due to the increased number of dot patterns, which allow a wider range of apparent shades of grey to be reproduced. Here is our camel and gradient built with the 4x4 patterns generated from our table:  The spots are, in general, much smaller than in the first set of patterns we looked at, and the gradient is reasonably convincing, although it does appear to be divided into little blocks. Figure K shows our camel picture using these sorts of small-dot dither patterns of sizes 2x2, 4x4, and 8x8. The difference is even more obvious when we use the gradient:  #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 92 Context: 78Chapter6.SavingSpaceProblemsSolutionsonpage154.1.CountthefrequenciesofthecharactersinthispieceoftextandassignthemtotheHuffmancodes,fillinginthefollowingtable.Thenencodethetextupto“morelightly.”.’IhaveatheorywhichIsuspectisratherimmoral,’Smileywenton,morelightly.’Eachofushasonlyaquantumofcompassion.Thatifwelavishourconcernoneverystraycat,wenevergettothecentreofthings.’LetterFrequencyCodeLetterFrequencyCode11111010010011001110111100100111110001011001011101000101010011010100000010010100010000010100101101101010011101010101100010100010110010001101011010110101010110112.Considerthefollowingfrequencytableandtext.Decodeit.LetterFrequencyCodeLetterFrequencyCodespace20111s200011e12100d2110101t91011T1110100h70111n1110011o70110w1110010m60100p1110001r50011b1010111 #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 159 Context: Chapter10.WordstoParagraphs145ProblemsSolutionsonpage166.Identifygoodhyphenationpointsinthefollowingwords:1.hyphenation2.fundraising3.arithmetic(noun)4.arithmetic(adjective)5.demonstration6.demonstrative7.genuine8.mountainous #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 34 Context: 20Chapter2.LetterFormsHowcanwedrawaBéziercurveonthescreenorprintitonpaper?Itseemsmuchmorecomplicatedthanthestraightlineswehavealreadydrawn.Itturnsout,though,thatthereisasimpleway:werepeatedlysplitupthecurveintosmallerandsmallersections,untileachoneisalmostasflatasaline.Then,wecandraweachofthoselittlelinesusingthemethodwedevelopedinChapter1.Howdoweperformsuchasubdivision?Wecouldpickequally-spacedpointsalongthelengthofthecurve.However,thiswouldusetoomanylineswherethecurveisopen,andtoofewwhenthecurveistight.Thefollowingalgorithm,devisedbydeCasteljau,issimpleenoughtodoonpaper,andproducesasubdivisionofthecurvewhichisappropriatetothetightnessofeachpart.Considerthiscurvewithend-pointsAandDandcontrolpointsBandC:ABCDABCDEFG #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 66 Context: 52Chapter4.LookingandFindingProblemsSolutionsonpage153.1.Runthesearchprocedureagainstthefollowingpatternsandthistext:ThesourceofsorrowistheselfitselfWhathappenseachtime?a)cowb)rowc)selfd)the2.Considerthefollowingkindofadvancedpatternsyntaxandgiveexampletextswhichmatchthefollowingpatterns.Aquestionmark?indicatesthatzerooroneofthepreviousletteristobematched;anasterisk*indicateszeroormore;aplussign+indicatesoneormore.Parenthesesaroundtwolettersseparatedbya|alloweitherlettertooccur.Theletters?,+,and*mayfollowsuchaclosingparenthesis,withtheeffectofoperatingonwhicheverletterischosen.a)aa+b)ab?cc)ab*cd)a(b|c)*d3.Assumingwehaveaversionofsearchwhichworksfortheseadvancedpatterns,givetheresultsofrunningitonthesametextasinProblem1.a)r+owb)(T|t)hec)(T|t)?hed)(T|t)*he #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 65 Context: Chapter4.LookingandFinding51realise.Thereareotherspecialcharacters:wecanuseafullstop.tomatchanycharacter,sothatthepattern.uncematchesounceanddunce.Inadditiontothesepatterns,wecanrunasearchmultipletimesandcombinetheresults.Forexample,whenusinganinternetsearchengine,ifweareinterestedinfindingdocumentscontaining“cats”or“dogs”wemightenterthesearch“catsORdogs”.ThesearchengineknowsthatthewordORisspecial,anditrunstwosearches,onefor“cats”andonefor“dogs”andreturnsdocumentswhichcontainaninstanceofeither.Inreality,searchenginesdon’tlookthroughthetextofwebpagesatthemomentthatyouclickthesearchbutton:theyusepre-preparedindexestomakethesearchmanymanytimesfaster.Intheproblemswhichfollow,weextendthisideaofpatterns,andaskyoutorunthesearchingalgorithmthroughonpapertodeterminewhethertheymatchthetext. #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 139 Context: Chapter9.OurTypeface125ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789(cid:362)(cid:363)(cid:364)(cid:365)(cid:366)(cid:367)(cid:368)(cid:369)(cid:370)(cid:371)IJ(cid:276)(cid:277)æœfiflffffiffl(cid:292)(cid:293)(cid:294)(cid:306)st(cid:308)(cid:309)(cid:278)(cid:279)(cid:280)(cid:107)NextaretheSmallCaps,whicharecapitalletterssettothesameheightaslowercaseletters.YoucanseeexamplesofSmallCapsinthefrontmatterofthisbook(thepartsbeforethefirstchapter).Noticethatthesmallcapsarenotjustscaled-downversionsoftheordinarycapitals–havingthesamegeneralweight,theymaybeusedalongsidethem.S(cid:1114)(cid:1102)(cid:1113)(cid:1113)C(cid:1102)(cid:1117)(cid:1120)S(cid:1114)(cid:1102)(cid:1113)(cid:1113)₁₂₃₄₅₆₇₈₉₀N(cid:1122)(cid:1114)(cid:1103)(cid:1106)(cid:1119)(cid:1120)ÄÀÅÁÃĄÂÇäàåáãąâç@£$%¶†‡©¥€`'``''!?(){}:;,./(cid:106)Next,wehaveaccentedletters,ofwhichonlyatinyportionareshownhere.Accentsattachindifferentplacesoneachletter,somanytypefacescontainanaccentedversionofeachcommonletter-accentpair,togetherwithseparateaccentmarkswhichcanbecombinedwithotherlettersasrequiredformoreesotericuses.S(cid:1114)(cid:1102)(cid:1113)(cid:1113)C(cid:1102)(cid:1117)(cid:1120)S(cid:1114)(cid:1102)(cid:1113)(cid:1113)₁₂₃₄₅₆₇₈₉₀N(cid:1122)(cid:1114)(cid:1103)(cid:1106)(cid:1119)(cid:1120)ÄÀÅÁÃĄÂÇäàåáãąâç@£$%¶†‡©¥€`'``''!?(){}:;,./(cid:106)Finally,herearesomeofthemanyotherglyphsinPalatino,forcurrencysymbolsandsoforth,andsomeofthepunctuation:S(cid:1114)(cid:1102)(cid:1113)(cid:1113)C(cid:1102)(cid:1117)(cid:1120)S(cid:1114)(cid:1102)(cid:1113)(cid:1113)₁₂₃₄₅₆₇₈₉₀N(cid:1122)(cid:1114)(cid:1103)(cid:1106)(cid:1119)(cid:1120)ÄÀÅÁÃĄÂÇäàåáãąâç@£$%¶†‡©¥€`'``''!?(){}:;,./(cid:106) #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 197 Context: Indexaccentedletter,125acidwash,104acid-resistant,104advancement,126AlbrechtDürer,102algorithm,41ofdeCasteljau,20aliasing,8ampersand,16ANSI,58antialiasing,8ASCII,31AugustDvorak,58backslash,33backwardcompatibility,35baseline,126BézierPierre,17Béziercurve,17billboard,8bit,28,69bitpattern,69bold,123Braille,38burin,102burnishing,104byte,29,69carriagereturn,31Cartesiancoordinate,1CasteljauPaulde,17chain,ofcurves,18characteraccented,33printable,31checkerboardpattern,100Chinesetone,63ChristopherLathamScholes,53circlefromBeziercurves,23circulararc,16Citroën,17coatedpaper,4composingstick,142compression,65lossy,74computerprogram,43condition,44controlpoint,17coordinate,1copper,102counter,44curvecontinuous,18discontinuous,18flatness,22join,18smoothcontinuous,18subdivision,20Cyrillic,33,124183 #################### File: 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84Chapter7.DoingSumsWhenevaluatingx×x×x,theresultofthecomputationdoesn’trelyontheorderinwhichweevaluateit:wecando(x×x)×xorx×(x×x).However,computersliketofollowrulesexactly,sotypicallytheorderischosenwhentheexpressionisreadintothecomputer,eitherleftmost-firstorrightmost-first.Anexpressionlikethis,whichdependsonthevalueofavari-able,iscalledafunction.Inthiscase,we’vewrittenafunctionwhichfindsthecubeofanumber.So,let’snameit:cubex=x×x×xNow,wecangivethevalueofxexplicitly,writingitoutlikethis:cube50=⇒50×50×50=⇒50×2500=⇒125000Inthefirststep,wesubstitutedcube50withitsdefinition.Wecanviewthecomputationintreeformtoo:cube50=⇒××505050=⇒×250050=⇒125000Let’sintroducesomemoreinterestingoperatorsinourexpres-sions.Wewillintroducethe=orequalsoperator,andthespecialvaluestrueandfalse(noteveryvaluehastobeanumber).Now,wecanwritex=4,and,ifxisindeed4inthecurrentenvironment,wegettrue;otherwise,wegetfalse.Here,=istheoperator,andxand4aretheoperands.Intheexpression1+2theoperatoris+,andtheoperandsare1and2.Now,wecanbuildamorecomplicatedoperatorwhichcanmakeadecisionbetweentwosub-expressionsbasedonanequalitytestlikethis.Forexample,wemaywrite:ifx=4then0elsex+1 #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 140 Context: 126Chapter9.OurTypefaceS(cid:1114)(cid:1102)(cid:1113)(cid:1113)C(cid:1102)(cid:1117)(cid:1120)S(cid:1114)(cid:1102)(cid:1113)(cid:1113)₁₂₃₄₅₆₇₈₉₀N(cid:1122)(cid:1114)(cid:1103)(cid:1106)(cid:1119)(cid:1120)ÄÀÅÁÃĄÂÇäàåáãąâç@£$%¶†‡©¥€`'``''!?(){}:;,./(cid:106)Howdowepicklettersfromthetypefaceandplacethemonthepage?Eachglyphcontainsnotonlythelinesandcurveswehavediscussedearlierinthebooks,butwhatareknownasmetrics;thatistosayasetofnumbersgoverninghowtheletterrelatestoitspreviousoneshorizontally,andwhereitliesvertically.Variousofthesenumberscanbeusedtofitletterstogetherpleasingly.Themostimportantmetricsarethebaselineandtheadvancement.Thebaselineisjustlikethelineonaschoolchild’sruledpaper–capitalletterssitonit,letterswithdescenderslike“g”and“y”dropsome-whatbelowit.Everyglyphisdefinedinrelationtothisbaseline,sowecanplaceitinthecorrectverticalposition.Theadvancementtellsushowmuchtomovetotherightafterdrawingtheglyph;thatistosay,howfartheoriginhasmoved.So,atthebeginningofaline,westartatanx-coordinateofzeroandmoverightwardsbytheadvancementeachtime.BaselineAdvancementBounding BoxAscentDescentThediagramshowsthreeglyphs,showingvariousmetrics:someareneededforplacingthemonthepageandsomeinfor-mationusedforotherpurposes.Thepositionofthelettersinalinedependsnotonlyontheindividualcharacters(theletter“i”ismuchnarrowerthantheletter“w”,forexample),butonthecombinationsinwhichtheyareprinted.Forexample,acapitalVfollowedbyacapitalAlooksoddifthespacingisnottightened: #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 144 Context: 130Chapter9.OurTypefaceWehavelookedatsomeofthesurprisingcomplexitiesofasimpletypeface,andhowitscharactersarepickedandplacednexttoeachothertoformlines.TypefacesforEasternalphabetsandwritingsystemsareevenmorecomplex.Tofinish,weexhibitthefull1328glyphsofthePalatinoRomantypefaceonthenextthreepages.Canyouworkoutwhateachglyphisusedfor? #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 97 Context: Chapter7.DoingSums83soon.Thesequantitiesarenotfixed,butcanbedifferenteachtime.Wecallthemvariables.Forexample,hereisanexpressionwhichcalculatesthecubeofagivennumberx:××xxxWhenweevaluatethisinanenvironmentinwhichx=4,wegetoneresult:××xxx=⇒××444=⇒×164=⇒64Whenweevaluateit,instead,inanenvironmentinwhichx=50,wegetanother:××xxx=⇒××505050=⇒×250050=⇒125000Ofcourse,wecanwritethesamethingoutonasingleline,andevaluateitwithoutdrawingthetreeexplicitly:x×x×x=⇒50×50×50=⇒50×2500=⇒125000 #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 126 Context: # Chapter 8. Grey Areas  We only have five different shades of grey, and the image suffers for it: we can see areas which in the original image were subtly shaded as plain, flat sections – not a good result. Let's double the length of the side of our square to 4. Now, we will have \(4 \times 4 + 1 = 17\) different levels of grey, but the image will have fewer dots overall. Will the increase in the number of shades outweigh the decrease in apparent resolution? Here is the generating table: | 15 | 10 | 8 | 14 | |----|----|----|----| | 5 | 1 | 2 | 12 | | 11 | 3 | 4 | 6 | | 13 | 7 | 9 | 16 | Here are the resultant 17 dither patterns. Again, they form a cohesive spot, and are built up somewhat symmetrically: | | | | | |----|----|----|----| | | | | | | | | | | | | | | | | | | | | #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 199 Context: INDEXJointPhotographicExpertsGroup,75JPEG,75justificationfull,136,137KafkaFranz,135kerning,127,136keyboard,27,53keyword,43laserprinter,4Latinalphabet,61leading,136ligature,50,124lineantialiased,8drawing,5linefeed,31LinearA,39linesperinch,108liningnumbers,124Linotype,123list,88reversing,90sorting,91lossycompression,74LouisSteinberg,118lpi,108mark-up,33mezzotint,102microtypography,139ModernGreek,61,124monitor,8negative,106newspaper,3newsprint,3niello,102non-zerorule,24oldstylenumbers,124operand,85operator,84opticalfontsize,128OR,51ordereddither,114origin,2orphan,139output,27Palatino,15,123paragraph,135parameter,43parenthesesinanexpression,82path,18containingahole,23filling,24self-crossing,24pattern,51PauldeCasteljau,17PDFfile,3photograph,97,106phototypesetting,144PierreBézier,17PierredeFermat,1Pinyin,61pixel,3,15plate,101point,2Polybius,27position,1prefix,70program,43,81psuedocode,43pt,2QWERTYkeyboard,58ragged-right,137RembrandtvanRijn,104Remington&Sons,53RenéDescartes,1 #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 13 Context: AMACHINEMADETHISBOOKtensketchesofcomputerscience #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 29 Context: Chapter2LetterFormsWehavelearnthowtobuildshapesfromstraightlinesandhowtodrawthoselinesontoascreenbuiltfrompixelsorontopaperusingink.Ifweonlyeverdrewourshapesatonesize,wecouldjustuseenoughtinylittlestraightlinestobuildupanyshape,includingcurvedones.However,wemightliketodrawourshapesatdif-ferentsizes,ordisplaythemondeviceswithdifferentresolutions.(Theremaybe1200dotsperinchonacommercialprinter,forex-ample,butonly200dotsperinchonacomputerscreen.)Wedon’treallywanttostoreahundredlittlelinesandtheircoordinatestodescribeacircle–weshouldjustliketosay“acircleofradius20ptatcoordinates(200,300)”,forexample.Considertheshapeswhichmakeupaletterofatypeface–Palatino,forexample,whichisusedinthisbook.Atypefaceisacollectionoflittleshapes,oneforeachletter,whicharearrangedonthepageinlines.Wemustbeabletoscalethemtodifferentsizes(large,forexample,forchapterheadings,orsmallerforfootnotes).Theymostoftencontaincurvesaswellasstraightlines.ConsidertheletterC,whichhascurvedparts.ThefollowingdiagramshowstheeffectofincreasingthesizeofaletterCdesignedusingonlylines:15 #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 103 Context: Chapter7.DoingSums89Letuswriteafunctiontofindthelengthofalistusingthetailfunction:lengthl=ifl=[]then0else1+length(taill)Theemptylisthaslength0,andthelengthofanyotherlistis1plusthelengthofitstail.Noticethatthe=operatorworksonliststoo.Wecantryasampleevaluation:length[2,3]=⇒if[2,3]=[]then0else1+length(tail[2,3])=⇒iffalsethen0else1+length(tail[2,3])=⇒1+length(tail[2,3])=⇒1+length[3]=⇒1+if[3]=[]then0else1+length(tail[3])=⇒1+iffalsethen0else1+length(tail[3])=⇒1+(1+length(tail[3]))=⇒1+(1+length[])=⇒1+(1+if[]=[]then0else1+length(taill))=⇒1+(1+iffalsethen0else1+length(taill))=⇒1+(1+0)=⇒1+1=⇒2Thesediagramsarebecomingalittleunwieldy,soaswewritemorecomplicatedfunctions,wewillleavesomeofthedetailout,concentratingontherepeatedusesofthemainfunctionwearewriting,herelength:length[2,3]=⇒1+length[3]=⇒1+(1+length[])=⇒1+(1+0)=⇒2 #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 179 Context: # Solutions 3 | | | | | | | | | | | |---|---|---|---|---|---|---|---|---|---| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |  | Color Gradient | |----------------| |  | #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 125 Context: # Chapter 8. Grey Areas ## 111 At the top, the finest halftone; at the bottom, the coarsest. We can see that the larger number of apparent grey in the coarsest dots are an advantage in this case: the top line looks very fragmented indeed. At a distance, the middle and bottom are both good. We can perform this halftoning by producing patterns which look like increasing sizes of ink dots. These patterns can then be displayed on screen or printed. To do this, we divide the image up into little 2x2 or 4x4 squares of pixels, and then choose one of a set of patterns to represent the average level of grey in the square. The result is a picture with the same number of pixels, but where each is black or white. Here are the patterns for a 2x2 scheme: | Pattern 1 | Pattern 2 | |-----------|-----------| |  |  | |  |  | Notice that there are five patterns, not four as we might expect. We use the first pattern for a grey level between 0% and 20%, the second between 20% and 40%, and so forth. In this scheme, we have tried to keep the black dots adjacent to one another to build up little spots, which is better suited to the spreading behaviour of ink on paper. The process is known as **dithering**. The patterns above may be generated by listing the order in which they turn black in a table: | 1 | 2 | |---|---| | 3 | 4 | So, for the third pattern, we blacken all pixels with values less than three (that is, one and two). It is known as an **ordered dither** for this reason. Here is the result:  #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 55 Context: Chapter4LookingandFindingWhenwritingabook,itisimportanttobeabletowrangleefficientlyalongpieceoftext.Oneimportanttaskistosearchforaword,find-ingwhereithasbeenused:wemaythenjumptosuchapositioninthetext,seewhatisaroundtheword,andmodifyorreplaceit.Weneedtodothisondemand,withoutanexplicitlypreparedindex.Infact,wehaveindexesatthebackofbooksbecausesearchingthroughthebookmanually,fromfronttoback,isslowanderrorproneforahuman.Luckily,itisfastandaccurateforacomputer.Itmightseemthatitiseasytodescribetoacomputerhowtosearchforaword:justlookforit!Butwemustprepareanexplicitmethod,madeoftinylittlesimplesteps,forthecomputertofollow.Everythingmustbeexplainedinperfectdetail–nobigassumptions,nohand-waving.Suchacareful,explicitmethodiscalledanalgorithm.Whatarethebasicoperationsfromwhichwecanbuildsuchanalgorithm?Assumewehavethetexttobesearched,andthewordtosearchfor,athand.Eachofthemismadeupofcharacters(A,x,!etc).Assumealsothatweknowhowtocomparetwocharacterstoseeiftheyarealikeordifferent.Forexample,AisthesameasAbutdifferentfromB.Letuspickaconcreteexample:weshalltrytofindtheword“horses”inthetext“housesandhorsesandhearses”.Letusnumbereachofthe29charactersinthetextandthe6charactersintheword:41 #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 105 Context: Chapter7.DoingSums91checkthatitworks(again,inourshortenedformofdiagram):reverse[1,2,3]=⇒reverse[2,3]•[1]=⇒(reverse[3]•[2])•[1]=⇒(([3]•reverse[])•[2])•[1]=⇒(([3]•[])•[2])•[1]=⇒[3,2,1]Letusapproachamorecomplicatedproblem.Howmightwesortalistintonumericalorder,whateverorderitisintostartwith?Forexample,wewanttosort[53,9,2,6,19]toproduce[2,6,9,19,53].Theproblemisalittleunapproachable–itseemsrathercomplex.Onewaytobeginistoseeifwecansolvethesimplestpartoftheproblem.Welljustlikeforreverse,sortingalistoflengthzeroiseasy–thereisnothingtodo:sortl=ifl=[]then[]else...Ifthelisthaslengthgreaterthanzero,ithasaheadandatail.Assumeforamomentthatthetailisalreadysorted–thenwejustneedtoinserttheheadintothetailatthecorrectpositionandthewholelistwillbesorted.Hereisadefinitionforsort,assumingwehaveaninsertfunction(weshallconcoctinsertinamoment):sortl=ifl=[]then[]elseinsert(headl)(sort(taill))Ifthelistisempty,wedonothing;otherwise,weinserttheheadofthelistintoitssortedtail.Assuminginsertexists,hereisthewholeevaluationofoursortingprocedureonthelist[53,9,2,6,19],showingonlyusesofsortandinsertforbrevity:sort[53,9,2,6,19]=⇒insert53(sort[9,2,6,19])=⇒insert53(insert9(sort[2,6,19]))=⇒insert53(insert9(insert2(sort[6,19])))=⇒insert53(insert9(insert2(insert6(sort[19])))) #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 39 Context: Chapter2.LetterForms25Ourlinecrossestwoanti-clockwiselinesandisthereforenon-zero(ithasacountof0−1−1whichis−2).WecanapplythisruletoourOexampletoo,butthereisaproblem:theinnerholeisfilledtoo:Thiscanbefixedbyreversingthedirectionofeitherofthetwopaths.Wenowhaveamethodwhichworksforbothcases:Nowthatwehavesomeunderstandingofhowtodrawlinesandcurvesontopaperorthescreen,wewillturntotheinput,storage,andmanipulationoftextitself,beforereturningtothevisuallayoutofthepagelaterinthebook. #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 84 Context: 70Chapter6.SavingSpacet00a01i10h11o000......Thereisaproblem,though.Itisveryeasytoencodeaword;forexample,“heat”encodesas1110100(thatis,11for“h”,1for“e”,01for“a”,and00for“t”).However,wecandecodeitinmanydifferentways.Thesequence1110100mightequallybetakentomean“eeespaceespace”or“hiispace”.Ourcodeisambiguous.Whatwerequireisacodewiththeso-calledprefixproperty–thatis,arrangedsuchthatnocodeinthetableisaprefixofanother.Forexample,wecannothaveboth001and0010ascodes,since001appearsatthebeginningof0010.Thispropertyallowsforunambiguousdecoding.Considerthefollowingalternativecode:space00e010t011a100i101h110o111......Thiscodeisunambiguous–nocodeisaprefixofanother.Theword“heat”encodesas110010100011andmaybedecodedun-ambiguously.Wecanhavethecomputerautomaticallycreateanappropriatecodeforourtext,takingintoaccountthefrequencies.Then,bysendingthecodetablealongwiththetext,weensureitmaybeunambiguouslydecoded.Hereisthefulltableofunam-biguouscodesforthefrequenciesderivedfromourtext:space111l10100,000100e100w00011.0101101t1011p110101k11000011a0111m110100j11000001i0110g110011T11000000 #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 40 Context: 26Chapter2.LetterFormsProblemsSolutionsonpage149.1.PrintoutortracethefollowingBéziercurve,anddivideitintotwo,usingtheprocedureofdeCasteljau.Youwillneedapencilandruler.2.Ifyouhaveaccesstoacomputer,findadrawingprogramwithBéziercurves,andexperimenttogainanintuitiveun-derstandingofhowtheyaremanipulated.Atthetimeofwriting,onesuchfreeprogramisInkscape,suitableformostcomputers.3.Fillinthefollowingshapesusingtheeven-oddfillingruleandagainusingthenon-zerofillingrule.Thedirectionofeachlineisindicatedbythelittlearrows.Thesecondandthirdpicturescontaintwoseparate,overlappingsquarepaths. #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 57 Context: Chapter4.LookingandFinding43Ifwereachasituationwherethewordoverrunstheendofthetext,westopimmediately–nofurthermatchcannowbefound:12T01234567890123456789012345678housesandhorsesandhearsesW012345horsesLetustrytowriteouralgorithmoutasacomputerprogram.Aprogramisasetofinstructionswritteninalanguagewhichisunderstandableandunambiguous,bothtothecomputerandtothehumanbeingwritingit.First,weshallassumethatthepartoftheprogramforcomparingthewordwiththetextatagivenpositionalreadyexists:wewillwriteitlater.Fornow,weshallconcentrateonthepartwhichdecideswheretostart,wheretostop,movesthewordalongthetextposition-by-position,andprintsoutanypositionswhichmatch.Forreasonsofconciseness,wewon’tusearealprogramminglanguagebutaso-calledpsuedocode–thatistosay,alanguagewhichcloselyresemblesanynumberofprogramminglanguages,butcontainsonlythecomplexitiesneededfordescribingthesolutiontoourparticularproblem.First,wecandefineanewalgorithmcalledsearch:definesearchpt1Weusedthekeyworddefinetosaythatwearedefininganewalgorithm.Keywordsarethingswhicharebuiltintotheprogram-minglanguage.Wewritetheminbold.Thenwegaveitthenamesearch.(Thisisarbitrary–wecouldhavecalleditcauliflowerifwehadwanted.)Wegivethenameofthethingthisalgorithmwillworkwith,calledaparameter–inourcasept,whichwillbeanumberkeepingtrackofhowfaralongthesearchingprocessweare(ptforpositionintext).Weshallarrangeforthevalueofpttobeginat0–thefirstcharacter.Ouralgorithmdoesn’tdoanythingyet–ifweaskedthecomputertorunit,nothingwouldhappen.Now,whatweshouldliketodoistomakesurethatwearenotoverrunningtheendofthetext–ifweare,therecanbenomorematches.WearenotoverrunningifthepositionptaddedtothelengthofthewordWislessthanorequaltothelengthofthetextT,thatistosaybetweenthesetwopositions: #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 189 Context: Templates175Problem1.40246810121416182002468101214161820xy0246810121416182002468101214161820xy0246810121416182002468101214161820xy0246810121416182002468101214161820xy #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 54 Context: 40Chapter3.StoringWordsProblemsSolutionsonpage151.1.UsingthemethodofPolybius,encodethephrase“MARY-HADALITTLELAMB”.Howmanycharactersareinthemes-sage?Howmanynumbersareneededtoencodethem?Canyouthinkofawaytoindicatetheconceptof“endofmessage”inPolybius’ssystem?Whataboutspaces?2.Completeatableofbits,numbers,andlettersforasystemwhichusesfivebitsforeachcharacter.Howmanylinesdoesthetablehave?Whichcharactersdidyoudeemimportantenoughtoinclude?3.DecodethefollowingmessagefromASCII:8411410197115111110105115118101114121109117991049710997116116101114111102104979810511644831091051081011211001019910510010110046.4.EncodethefollowingmessageintoASCII:Themoreidentitiesamanhas,themoretheyexpressthepersontheyconceal.5.Inamark-uplanguageinwhich\istheescapecharacter,andapairof$saroundawordmeansitalicandapairof*saroundawordmeanbold,givethemarked-uptextforthefollowingliteralpiecesoftext:a)Theloveofmoneyistherootofallevil.b)Theloveof$$$istherootofallevil.c)Theloveof$$$istherootofallevil.d)Theloveof$$$istherootofallevil. #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 121 Context: # Chapter 8. Grey Areas ## Figure G: Film grain  ## Figure H: Film under an electron microscope  #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 87 Context: Chapter6.SavingSpace73problemofhavingtogatherfrequencydataforthewholepage,apre-preparedmastercodetableisused,uponwhicheveryoneagrees.Thetablehasbeenbuiltbygatheringfrequenciesfromthousandsoftextdocumentsinseverallanguagesandtypefaces,andthencollatingthefrequenciesofthevariousblackandwhiteruns.Hereisthetableofcodesforblackandwhiterunsoflengths0to63.(Weneedlength0becausealineisalwaysassumedtobeginwhite,andazero-lengthwhiterunisrequiredifthelineactuallybeginsblack.)RunWhiteBlackRunWhiteBlack000110101000011011132000110110000011010101000011101033000100100000011010112011111340001001100001101001031000103500010100000011010011410110113600010101000011010100511000011370001011000001101010161110001038000101110000110101107111100011390010100000001101011181011000101400010100100000110110091010000010041001010100000011011011000111000010042001010110000110110101101000000010143001011000000110110111200100000001114400101101000001010100130000110000010045000001000000010101011411010000000111460000010100000101011015110101000011000470000101000000101011116101010000001011148000010100001100100171010110000011000490101001000000110010118010011100000010005001010011000001010010190001100000011001115101010100000001010011200001000000011010005201010101000000100100210010111000011011005300100100000000110111220000001100000110111540010010100000011100023000010000000101000550101100000000010011124010100000000010111560101100100000010100025010101100000011000570101101000000101100026001001100001100101058010110110000010110012701001000000110010115901001010000000101011 #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 27 Context: Chapter1.PuttingMarksonPaper130246810121416182002468101214161820xy0246810121416182002468101214161820xy4.On20x20grids,choosepixelstofillintoapproximatethefollowingcharacters.Keeptheminproportiontooneanother.Xt?© #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 116 Context: # Chapter 8: Grey Areas  The term engraving, in the context of printing, refers to the use of the tools traditionally used for engraving decoration on, for example, decorative silver-work, on metal plates instead, which are then used for printing. Decorative metal engravers had used more primitive versions of this technique to "print" their work-in-progress when designing **nitello**, a type of decoration where engraved lines were filled with a black substance and polished for contrast. Making proof prints with ink helped to show what the final design might look like when blackened. In the late fifteenth century, engraving began to be used for the reproduction of simplified versions of paintings and for original works. A copper plate would be inscribed with a hard metal tool known as a **burin**. The plate could then be used to produce hundreds of copies of a print. (Copper being soft, and the printing being done under pressure, it would eventually produce faded prints.) Engraving was a highly skilled and difficult process. Figure B is a relatively simple and coarse engraving, a detail of **Der Kreuzbrunnen zu Marienbad** published by Franz Sator in 1819. Figure C is a much more accomplished and fine engraving, **Melencolia I**, by the German master Albrecht Dürer. Alternative intaglio methods were developed, hoping to improve the fineness of the result, or lessen the amount of expertise required. The **mezzotint** method, from the Italian "mezzo tinto," #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 171 Context: ```markdown # Solutions | Colour | Length | Code | |--------|--------|--------| | Black | 9 | 000100 | | White | 3 | 1000 | | Black | 2 | 11 | | White | 37 | 0001010 | So we have: ``` 000101101011111100101011110000010 0110101000111110010100010101110001 0011000101101101001000110011001010 0101011111001000111101101010011011 0111101111100101110111011011100110 1110011000000001110010100000011101 0001000111111111100100001111111011 ``` ## The codes are: | Code | Length | Colour | Code | Length | Colour | |----------|--------|---------|----------|--------|---------| | 0001010 | 37 | White | 000100 | 9 | Black | | 0000111 | 1 | White | 0111 | 2 | White | | 000011 | 7 | Black | 11 | 2 | Black | | 000011 | 7 | Black | 10 | 3 | Black | | 1100 | 5 | White | 000011 | 1 | White | | 1000 | 3 | Black | 1100 | 5 | White | | 000010 | 9 | Black | 1110 | 6 | White | | 11 | 2 | Black | 11 | 2 | Black | | 1000 | 3 | Black | 10 | 3 | Black | | 0111 | 2 | White | 0000111 | 1 | White | ``` #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 2 Context: AMACHINEMADETHISBOOKtensketchesofcomputerscienceHowdowedecidewheretoputinkonapagetodrawlettersandpictures?Howcancomputersrepresentalltheworld’slanguagesandwritingsystems?Whatexactlyisacomputerprogram,whatandhowdoesitcalculate,andhowcanwebuildone?Canwecompressinformationtomakeiteasiertostoreandquickertotransmit?Howdonewspapersprintphotographswithgreytonesusingjustblackinkandwhitepaper?Howareparagraphslaidoutautomaticallyonapageandsplitacrossmultiplepages?InAMachineMadethisBook,usingexamplesfromthepublish-ingindustry,JohnWhitingtonintroducesthefascinatingdisciplineofComputerSciencetotheuninitiated.JOHNWHITINGTONfoundedacompanywhichbuildssoftwareforelectronicdocumentprocessing.Hestudied,andtaught,ComputerScienceatQueens’College,Cambridge.Hehaswrittentextbooksbefore,butthisishisfirstattemptatsomethingforthepopularaudience. #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 99 Context: Chapter7.DoingSums85(Thisisonlysomewhatrelatedtotheif...then...elsecon-structofChapter4–pleaseputitoutofyourmind.)Asamathe-maticalconstruct,thislooksratherstrange:weareusedtoseeingoperatorslike+and×,whichconsistofonesymbolandhaveanoperandeitherside.Thisnewoperatorhasthreeparts(if,then,andelse)andthreeoperands(x=4,0,andx+1),andtheyarespreadallovertheplace!Butifwewriteitoutasatree,itlooksmuchliketheearliertrees:if...then...else+1x0=4xAnoperatorhavingmorethantwooperandsisnotsostrangeafterall.Supposeweevaluateitintheenvironmentwherex=6:if...then...else+160=46=⇒if...then...else+160false=⇒+16=⇒7Ofcourse,wecanwritethisoutinlinearform:if6=4then0else6+1=⇒iffalsethen0else6+1=⇒6+1=⇒7And,wecannamethefunction:testl=ifx=4then0elsex+1Wearegettingalittleclosertothesortsofcalculationsarealprogramdoes:makingdecisionsaboutwhichpartofanexpression #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 64 Context: 50Chapter4.LookingandFinding12T01234567890123456789012345678housesandhorsesandhearsesW012345horses3horses1horses1horses1horses1horses1horses1horses1horses1horses6horses1horses1horses1horses1horses1horses1Wehaveproducedaverysimplesearchingmethod,andshownhowitworks.Inreality,thingsaremorecomplex.Howdowedealwithcase(“Horses”vs.“horses”),differentpartsofspeech(“horsedaroundwith”),accents(“cafe”and“café”),ligatures(“haemoglobin”and“hæmoglobin”)andsoforth?Ofcourse,evenwithourexistingsearchprogram,wecansearchforthingsotherthanwords,suchas“!!”tolookforexcessivepunctuation,or“andand”tosearchforacommonmistake.Soletusstopcallingthethingwesearchfora“word”,andinsteadcallitapattern.Thesimplestexamplesofpatternsarejustwhatwehavebeenusingalready:theyfindonlyapieceofthetextwhichmatchesthepatternexactly.Moreadvancedpatternsconsistofspecialcharacterstoindicatealooseningoftherequirementsforoneormorecharacterstomatch.Forexample,wecanwriterealise|realizetosearchforeitherrealiseorrealize.(The|symbolisonyourcomputerkeyboard,ifyoulookcarefully.Inthiscontext,wepronounceit“or”becauseitlooksforthethingonitsleft,orthethingonitsright,matchingineithercase.)Infact,wecansimplifythispatternbyusingparenthesestolimittheoptionalsection,andwritereali(s|z)e.Thiswillstillmatchrealizeand #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 83 Context: Chapter6.SavingSpace69Wearedownto880characters,areductionofabout10%com-paredwiththeoriginal.Thetop100wordsinEnglishareknowntocoverabouthalfoftheprintedwords,ingeneral.Wehavenotquiteachievedthatinthisexample.Letustrycountingthenumberofeachcharacterinourtexttoseeifwecantakeadvantageofthefactthatsomelettersaremorecommonthanothers(ourcurrentmethodmakesnouseofthefactthat,forexample,spacesareverycommon):167space30l10,120e24w8.71t19p5k62a19m4j55i19g4T51h19c3q49o18u2x45r15y1W42n13f1K41s13b1I33d10v1BThespacecharacterisbyfarthemostcommon(wesayithasthehighestfrequency).ThefrequenciesofthelowercaselettersareroughlywhatwemightexpectfromrecallingthevalueofScrabbletiles,thepunctuationcharactersareinfrequent,andthecapitallettersveryinfrequent.Wehavetalkedaboutwhatabitis,how8bitsmakeabyte,andhowonebyteissufficienttostoreacharacter(atleastinEnglish).Ouroriginalmessageis975bytes,or975×8=7800bits.Wecouldencodeeachofthe33characterswehavefoundinourtextusingadifferentpatternof6bits,since33islessthan64,whichisthenumberof6-bitcombinations000000,000001,...,111110,111111.(Thenumberof5-bitcombinationsis32,whichisnotquiteenough.)Thiswouldreduceourspaceto975×6=5850bits.However,wewouldhavewastedmuchofthepossiblesetofcodesandtakennoadvantageofourknowledgeofhowfrequentlyeachcharacteroccurs.Whatweshouldlikeisacodewhichusesshorterbitpat-ternsformorecommoncharacters,andlongerbitpatternsforlesscommonones.Letuswriteoutthebeginningsofsuchacode:space0e1 #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 67 Context: Chapter5TypingitInItiseasytotakeforgrantedtheabilitytoenter,modify,andcorrectlargeamountsoftextaccuratelyandquickly,sincemostofushavesomeproficiencyatitthesedays.Butrememberthat,inthepast,hugenumbersofyoungpeoplewouldgotosecretarialschoolbeforetheycouldworkastypistsordataentryclerks.Thepresentgenerationmayusecomputerortabletkeyboardsfromchildhood,butthoseofuswhorememberhavingtolearntotypeasteenagersrecallhowharditseemedatthetime.Thedevelopmentofthekeyboardbeganbeforethecomputer,orcourse,fortypewritersandsimilarequipment.Andso,whencomputerswerefirstdeveloped,thebestmethodsfortextinputwerealreadyknown,requiringonlyslightalteration.Inthischap-ter,wewilllookatthedevelopmentoftypingdevicesfromthetypewritertothemoderncomputer.WewillalsoseemethodsfortypinglanguagessuchasChinese,wherethenumberofcharactersmightvastlyoutnumberthekeyswecouldpossiblyplaceonakeyboard.Asearlyastheeighteenthcentury,workwasbeginningonde-vicesfor“automaticwriting”,butwhatwerecognisetodayasatypewritercanbetracedbacktothefirstcommerciallysuccessfulexamples,theworkofthePennsylvania-bornnewspapereditorChristopherLathamScholes(1819–1890).Hiscompanywaseven-tuallysoldtoRemington&Sons,underwhosebrandtypewritersweresolduntilthe1960s.ThefollowingpagesshowimagesfromScholes’searlyandmorematurepatentapplications.53 #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 36 Context: 22Chapter2.LetterFormsThisprocedureworksforanyBéziercurve.Wecanproceedtosubdivideeachofthesesmallercurves.Oncewehavesubdividedenoughtimes,eachofthelittlecurvesshouldbeflatenoughtoberoughlyequivalenttoastraightlinebetweenitsendpoints.Sowecanjustdraweachasastraightline,usingtheproceduredescribedinChapter1.Howdowedecidewhentostopthesubdivision?Ifwestopafterafixednumberofstages,thedifferencebetweenthetreatmentofopenandtightpartsofthecurveagainbecomesapparent.Instead,wecalculateacrudemeasureofthe“flatness”ofacurve,andfinishwhenthatislessthanacertainamount(sayhalfthewidthofapixel).Alineisthenanappropriatesubstituteforthatcurve.HereisaBéziercurveapproximatedby1,2,4,6,7,10,13,21,and25straightlines,asaresultofrepeatedapplicationofdeCasteljau’sprocedure,stoppingwheneachsectionisflatenoughaccordingtoourtest:Hereisonesuchapproximatemeasureofflatness,whichisrelativelyeasytocalculate:the“height”ofthecurve.IfthelengthA+Binthediagrambelowislessthanagivensmallnumber,wecanapproximatethecurvewithaline.Thislengthwillalwaysbegreaterthanthemaximumdeviationofthecurvefromthestraightlinejoiningitsend-points. #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 129 Context: # Chapter 8. Grey Areas We still have five levels of grey, but the apparent resolution should be higher, and the eye should find it harder to discern individual dots, since we try to keep them as small as possible for as long as possible. Here is the camel and gradient, drawn with this new set of patterns:  Here is a similarly constructed 4x4 pattern giving, as before, 17 greys. Notice that it is built in such a way as to keep the spots as small as possible. ``` | | | | | |---|---|---|---| | 2 |16 | 3 |13 | |10 | 6 |11 | 7 | | 4 |15 | 1 |14 | |12 | 8 | 9 | 5 | ``` ``` | | | | | |---|---|---|---| | | | | | | | | | | | | | | | | | | | | ``` #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 163 Context: Solutions149Chapter21WeassignthelettersABCDasinthechaptertext:ABCDNow,wecontinuetheconstructionasbefore,makingsurewearenotconfusedbythefactthatthelineBCnowcrossesthecurve: #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 141 Context: Chapter9.OurTypeface127AVAVInthisexample,thereisnotighteningintheleft-handexample,buttighteninghasbeenappliedtotheright-handone.Suchtight-eningiscalledkerning.HerearesomeoftherulesfromPalatinoshowinghowmuchextraspaceisaddedorremovedwhenthecharacters“A”,“a”,“:”etc.followthecharacter“V”.VA-111Vhyphen-74Vr-92Va-92Vi-55Vsemicolon-55Vcolon-55Vo-111Vu-92Vcomma-129Vperiod-129Vy-92Ve-111VA-111VOslash-37VOE-37Vae-148Voslash-130Voe-130VAring-130Vquoteright28Thenumbersareexpressedinthousandthsofaninch.Forexample,youcanseethatwhenahyphenfollowsa“V”,thehyphenisplaced74/1000ofaninchclosertothe“V”.Kerningisespeciallyimportantwhenlettersmeetpunctuation.Palatinohad,inall,1031suchrulesforpairsofcharacters.Overlappingofadjacentletterscanalsobeachievedsimplybyextendingtheshapeofthecharacterbeyonditsboundingbox.ThefollowingdiagramshowstheparticularlystrikingoverlapsusedbythevariousalternativecharactersavailableinanotherofZapf’screations,thescript-likeZapfino.dawningdawningdawningdawningdawningdawningdawningdawning #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 118 Context: # Chapter 8. Grey Areas Figure D: Wiping excess ink from a mezzotint plate. Mezzotint, meaning “half-painted,” involves a device called a rocker to roughen the plate all over. Ink gathers in the little indentations made by such a process, leading to an entirely black image. Burnishing tools can then be used to flatten the copper in areas where ink is not wanted. Because this process is gradual (one may burnish more or less), the illusion of shades is easier to achieve. Figure D shows a mezzotint plate being wiped off ready for printing. Unfortunately, due to the softness of copper and the smallness of the indentations, these plates did not last long, and the quality of the printing declined with each pressing. Figure E shows a mezzotint print. Note the fineness of the grey tone reproduction. Another alternative to engraving is the process of etching, in which the whole plate is covered in an acid-resistant substance, which is then scratched off using tools in areas where the artist wants it to appear in the final print. The plate is then washed with acid, which roughens the metal in unprotected areas so that they will hold ink. The plate is then printed as with any other intaglio process. The great advantage is that the process is valuable to the general artist, who can draw in this medium without learning the difficult metalwork skills of the engraver. Improvements to the process include “stopping out,” where the plate is briefly dipped in the acid, more acid-resistant substance is added to certain areas, and then the plate is dipped again. This allows better control over grey tones. Figure F is an etching by Rembrandt, known as *The Hundred Guilder Print* after the sum reportedly once paid for a copy. #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 26 Context: 12Chapter1.PuttingMarksonPaperProblemsSolutionsonpage147.Gridsforyoutophotocopyorprintouthavebeenprovidedonpage173.Alternatively,usegraphpaperordrawyourowngrids.1.Givesequencesofcoordinateswhichmaybeusedtodrawthesesetsoflines.0246810121416182002468101214161820xy0246810121416182002468101214161820xy2.Drawthesetwosequencesofcoordinatesonseparate20x20grids,withlinesbetweenthepoints.Whatdotheyeachshow?(5,19)—(15,19)—(15,16)—(8,16)—(8,12)—(15,12)—(15,9)—(8,9)—(8,5)—(15,5)—(15,2)—(5,2)—(5,19)(0,5)—(10,10)—(5,0)—(10,3)—(15,0)—(10,10)—(20,5)—(17,10)—(20,15)—(10,10)—(15,20)—(10,17)—(5,20)—(10,10)—(0,15)—(3,10)—(0,5)3.Giventhefollowinglineson20x20grids,selectpixelstoap-proximatethem. #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 168 Context: 154SolutionsChapter61LetterFrequencyCodeLetterFrequencyCodespace41111u5110100e18100v4110011o141011w4110010t140111f4110001a130110’4010111h120100y3010101r110011.301010000n110010,301010001s100000p201010010i911011I201010011c810101q101011000m610100E101011001l600011S101011010g6110101T101011011Sowehave:'Ihavea01011101010011111010001101100111001110110111theorywhi0111010010010110011010101111110010010011011chIsusp101010100111010100111110000110100000001010010ectisrath1001010101111111101100001110011011001110100erimmoral100001111111011101001010010110011011000011,'Smiley0101000101011111101011010101001101100011100010101wenton,111110010100001001111111011001001010001111morelight1010010110011100111000111101111010101000111ly.0001101010101010000 #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 101 Context: Chapter7.DoingSums87=⇒4×(3×(iffalsethen1else2×factorial(2−1)))=⇒4×(3×(2×factorial(2−1)))=⇒4×(3×(2×factorial1))=⇒4×(3×(2×(if1=1then1else2×factorial(1−1))))=⇒4×(3×(2×(iftruethen1else2×factorial(1−1))))=⇒4×(3×(2×1))=⇒4×(3×2)=⇒4×6=⇒24Wesaidearlierthatwewantedtheexpressiontogetsmallereachstep.Thisisn’tthecasehere:werelaxthisrestrictiontosaysimplythatinaproperlyworkingprogramwithaproperinput,thecomputationeventuallyfinishes.Hereisthetreeforfactorial:factorialx=if...then...else×factorial−1xx1=1xConsideranothersimpletaskwithnumbers.Giventwonum-bersxandy,wewishtocalculatexy,whichispronounced“xtothepowery”.Thisisequaltoxmultipliedbyitselfytimes.So,forexample,25=2×2×2×2×2=32.Ontheotherhand,52=5×5=25.Notethatitisamathematicalconventionthatanynumbertothepower0is1.Thisfactallowsustobegintowritethepowerfunction(noticeithastwoinputs):powerxy=ify=0then1else... #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 100 Context: 86Chapter7.DoingSumstoevaluatebasedoninputdataanddefiningandusingreusablefunctions.Nowletuswriteareal,usefulfunction.Givenanumber,suchas4,itwillcalculatethefactorial,written4!,ofthenumber.Thefactorialofanumberisallthenumbersfrom1tothatnumbermultipliedtogether.Forexample,thefactorialof4is4×3×2×1,whichis24.Thenumberofpossibleorderingsofapackofplayingcardsis52!,whichisaverylargenumberindeed.Tocalculateafactorial,westartatthegivennumber,andwewanttokeepmultiplyingitbythenumberonesmallerandonesmallerandonesmaller,untilwereach1.Then,wewanttostop,ratherthankeepmultiplyingby0,−1,−2etc.Youcanseethatwewillhavetouseanif...then...elseconstructbecausewehaveadecisiontomake.Letusbegintodefineourfunction.Thefirstpartiseasy–ifthenumberis1,theansweris1:factorialn=ifn=1then1else...Nowwemustconsiderwhattodowhenthenumberisgreaterthan1.Inthiscase,wewanttomultiplythenumberbythefactorialofthenumberonesmallersince,forexample,4×3×2×1=4×3!Sowewriteitout:factorialn=ifn=1then1elsen×factorial(n−1)Noticethatourfunctionusesitselfwithinitsowndefinition.Thisisnotaproblemaslongasthecomputationeventuallycompletesandgivesaresult.Hereitisforthenumber4:factorial4=⇒if4=1then1else4×factorial(4−1)=⇒iffalsethen1else4×factorial(4−1)=⇒4×factorial(4−1)=⇒4×factorial3=⇒4×(if3=1then1else3×factorial(3−1))=⇒4×(iffalsethen1else3×factorial(3−1))=⇒4×(3×factorial(3−1))=⇒4×(3×factorial2)=⇒4×(3×(if2=1then1else2×factorial(2−1))) #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 198 Context: 184IndexDailyGraphic,108DavidA.Huffman,72deCasteljauPaul,17demerit,139DensmoreJames,55DescartesRené,1dictionary,67digitalhalftoning,111DijkstraEdsger,viidither,111ordered,114dotsperinch,3DürerAlbrecht,102DvorakAugust,58Dvorakkeyboard,58eBook,3,34Eckert-MauchlyComputerCorporation,60EDSAC,30EdsgerDijkstra,viiend-point,17engraving,102errordiffusion,118escapecharacter,33etching,104even-oddrule,24expression,81evaluating,81factorial,86false,45,84fax,72compression,72FermatPierrede,1filledshape,9firesignals,27FloydRobertW.,118FranzKafka,135frenchcurves,16frequenciesofcharacters,70fulljustification,136,137function,84galley,143glyphmetrics,126gradient,97Greekalphabet,27greytones,97halftone,106forcolour,114halftonescreen,108Hancharacters,33HermannZapf,123HuffmanDavidA.,72Huffmanencoding,72humanopticalsystem,8hyphenation,137dictionarybased,138if...then...else,44,85imageblackandwhite,98grey,98indenting,44index,41inhibitingrule,138ink-flow,114input,27system,61insert,91intaglio,101interoperability,29italic,34,123JamesDensmore,55 #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 188 Context: 174TemplatesProblem1.20246810121416182002468101214161820xy0246810121416182002468101214161820xyProblem1.30246810121416182002468101214161820xy0246810121416182002468101214161820xy #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 131 Context: # Chapter 8. Grey Areas ## Figure K Small-spot ordered dithers with 2x2, 4x4, and 8x8 patterns.    #################### File: A%20MACHINE%20MADE%20THIS%20BOOK%20ten%20sketches%20of%20computer%20science%20-%20JOHN%20WHITINGTON%20%28PDF%29.pdf Page: 86 Context: # Chapter 6. Saving Space A common use for this sort of encoding is in the sending of faxes. A fax consists of a high-resolution black and white image. In this case, we are not compressing characters, but the black and white image of those characters itself. Take the following fragment:  This image is 37 pixels wide and 15 tall. Here it is with a grid superimposed to make it easier to count pixels: ``` | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | ``` We cannot compress the whole thing with Huffman encoding, since we do not know the frequencies at the outset—a fax is sent incrementally. One machine scans the document whilst the machine at the other end of the phone line prints the result as it pulls paper from its roll. It had to be this way because, when fax machines were in their infancy, computer memory was very expensive, so receiving and storing the whole image in one go and only then printing it was not practical. The solution the fax system uses is as follows. Instead of sending individual pixels, we send a line at a time, a list of runs. Each run is a length of white pixels or a length of black pixels. For example, a line of width 30 might contain 12 pixels of white, then 4 of black, then 2 of white, then 18 of black, and then 3 of white. We look up the code for each run and send the codes in order. To avoid the #################### File: 15-MB-docx-file-download.pdf Page: 8 Context: Sed eu faucibus mi. Mauris luctus quis nisi ut egestas. Donec tempus turpis et dui dictum, a tincidunt nisl sagittis. Aliquam tristique vehicula dui eget dapibus. Sed arcu mauris, feugiat sed ex ac, consectetur finibus justo. Interdum et malesuada fames ac ante ipsum primis in faucibus. Donec malesuada, ligula vitae convallis fermentum, tellus mauris dictum justo, a blandit sapien arcu sit amet mi. Morbi porta metus elit, vel egestas ipsum tristique ut. Fusce euismod ante odio, ut interdum tellus imperdiet vitae. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Suspendisse commodo, tellus ac varius egestas, magna nisi condimentum nunc, vitae tincidunt nisl lorem eget eros. Duis tristique ultrices magna, a varius ligula ornare pharetra. Fusce luctus nisl est, ac semper nunc dignissim tempor. Praesent sed lorem lorem. Donec egestas eros nec rhoncus efficitur. Duis nec mi arcu. Suspendisse in elit elit. Suspendisse potenti. Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Quisque mattis metus eu nisi commodo, in semper orci malesuada. Nullam ullamcorper dapibus dolor in egestas. Aenean faucibus dui sit amet interdum laoreet. Sed ac pretium arcu, at dictum nisl. Donec ullamcorper ac diam et finibus. Suspendisse hendrerit lorem sem, ut mattis ipsum malesuada vel. Morbi ullamcorper elementum viverra. Fusce eget placerat urna, et ornare tortor. Suspendisse facilisis lorem at nunc semper rhoncus. Quisque volutpat non est vitae dapibus. Suspendisse imperdiet facilisis nibh nec sodales. Cras sagittis porttitor odio, in pretium mauris finibus ut. Aliquam venenatis magna massa, id accumsan mi blandit quis. In vehicula euismod mollis. Donec volutpat, tortor in auctor cursus, urna nibh scelerisque magna, nec consectetur odio magna nec nisi. Suspendisse commodo euismod diam eget rutrum. Suspendisse vel laoreet ex. In sed sodales nisl. Sed et hendrerit magna. Suspendisse pulvinar id elit sit amet scelerisque. Suspendisse dictum nisl in sapien iaculis ultrices in a risus. In tristique sapien est, vel mollis magna egestas at. Aenean ullamcorper nisl at metus feugiat, non egestas urna bibendum. Quisque pharetra ac nunc at tincidunt. Nulla vel ipsum nec elit blandit hendrerit. Quisque magna eros, imperdiet non elementum id, blandit nec eros. Etiam pharetra condimentum mi, sit amet dictum dolor vulputate ut. Nam pellentesque velit a ullamcorper condimentum. Integer orci dui, elementum non augue non, accumsan facilisis augue. Phasellus pharetra lorem et eros vehicula varius. Vestibulum elementum nunc eget sagittis laoreet. Suspendisse mauris massa, aliquet sed eros ac, tempus elementum nisl. Integer vel congue libero, at sagittis dui. Aliquam viverra nisl dolor, ac volutpat neque maximus vel. Etiam faucibus fermentum nulla malesuada rutrum. Pellentesque imperdiet tincidunt augue. Phasellus sagittis quis justo gravida placerat. Praesent congue mattis nulla, vitae vehicula tortor efficitur in. Maecenas cursus odio risus, dictum molestie enim pulvinar ut. Praesent nibh erat, accumsan a tellus vel, fringilla ultrices sem. Donec vel enim a orci mollis scelerisque. Mauris at imperdiet metus. Nulla commodo fermentum ex a varius. Morbi ac quam non nisl pellentesque feugiat. Praesent a aliquet elit, vitae imperdiet felis. Donec bibendum ipsum metus, quis rhoncus orci convallis at. Duis pharetra nisl id blandit malesuada. Donec sodales a eros fringilla congue. Etiam eleifend massa non sapien viverra fringilla. Vivamus tempor sodales ante eu finibus. Phasellus sit amet elementum diam. Phasellus eget diam diam. Nunc rutrum lacus ut elementum congue. Donec justo felis, tempus ac sodales vitae, faucibus sit amet nibh. Nam consequat sit amet nisi a hendrerit. Ut auctor non lectus eu semper. Curabitur sollicitudin libero vitae ante pulvinar, vel laoreet nunc finibus. Praesent vel convallis est. Interdum et malesuada fames ac ante ipsum primis in faucibus. Morbi efficitur odio ac tortor consequat, eget vehicula odio vulputate. Nunc ut eros ante. Donec ornare mi sit amet enim porttitor, a tincidunt mauris laoreet. Aenean scelerisque eu eros nec euismod. Fusce ut turpis turpis. Integer justo nibh, efficitur eu dignissim at, mattis eu arcu. Curabitur luctus libero fringilla risus bibendum tincidunt. Morbi ullamcorper, leo ut tincidunt posuere, lacus augue placerat nisl, eget lacinia eros ante sed risus. Vestibulum neque ante, feugiat vel vestibulum eu, faucibus sit amet arcu. Curabitur consectetur nunc sed rutrum fringilla. ########## """QUERY: Please summarize the topic""" Consider the chat history for relevant information. If query is already asked in the history double check the correctness of your answer and maybe correct your previous mistake. If you find information separated by a | in the context, it is a table formatted in Markdown - the whole context is formatted as md structure. 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Page 86, 15-MB-docx-file-download.pdf - Page 8 ================================================== **Elapsed Time: 10.91 seconds** ================================================== FINAL ANSWER Answer: The document "A Machine Made This Book: Ten Sketches of Computer Science" by John Whitington explores various aspects of computer science through the lens of book production. It addresses topics such as: 1. **Input and Representation**: How computers represent languages and characters, including the use of different input systems for languages with extensive character sets, like Chinese. 2. **Drawing and Typesetting**: Techniques for drawing shapes and letters on screens and paper, including Bézier curves and the importance of resolution in printing. 3. **Data Compression**: Methods for reducing the size of data for efficient storage and transmission, including Huffman coding and the challenges of compressing images. 4. **Image Processing**: The conversion of grey tones in images to black and white for printing, discussing techniques like dithering and halftoning. 5. **Text Layout**: The automatic layout of paragraphs and the complexities of hyphenation and justification in typesetting. 6. **Programming Concepts**: Basic programming principles, including functions, recursion, and algorithms for searching and sorting data. The book aims to demystify computer science concepts for a general audience by using relatable examples from the publishing industry. ================================================== **Elapsed Time: 0.06 seconds** ==================================================