williams-et-al-1983-apple-ii-computer-graphics

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148 APPLE II COMPUTER GRAPHICSprovided by a scoreboard in Hi-Res; the digits keep changing in a predictablemanner, and you can use that fact to shorten your code. Enter and runthe following program (you may omit the REM statements if you wish).1 REM PARTIAL MOD .2 REM3 HGR4 REM5 REM POKE EIGHT6 REM7 POKE 8192,6 : POKE 9216,66:POKE 124,66: POKE 11264,68 POKE 12288,66: POKE 13312 ,66:POKE 14336,6: POKE 1536,9 VTAB (24) : PRINT "PRESS A KEY 11 •GET R$1 REM11 REM POKE NINE12 REM13 POKE 8192,6 : POKE 9216,66:POKE 124,66: POKE 11264,614 POKE 12288,64: POKE 13312 ,64:POKE 14336,6: POKE 1536,15 VTAB (24) : PRINT "PRESS A KEY"GET R$16 REM17 REM POKE ZERO18 REM19 POKE 8192,6: POKE 9216,66:POKE 124,66: POKE 11264,662 POKE 12288,66: POKE 13312,66:POKE 14336,6: POKE 1536,21 VTAB (24) : PRINT "PRESS A KEY" :GET R$22 GOTO 7Listing 13-1.
CHAPTER 13-ADVANCED MOVES 149When you have everything keyed in correctly, you will see the digitseight, nine, and zero cycle on the Hi-Res screen. This was easily done byPOKEing the appropriate dot patterns into screen memory.For example, the numerals.eight and nine are composed of eight rows ofdots which correspond to byte values as shown below.DOT BIT DECIMAL DOT BIT DECIMALPATTERN PATTERN VALUE PATTERN PATTERN VALUE------------------------------------------------------------XXXX--X----X-X----X--XXXX--X----X-X----X--XXXX--------!il!illl ll!iJ!iJ!ill!il!il !il!ill!il!ill!il!il !il!ill!il!il!illl ll!iJ!iJ!ill!il!il !il!ill!il!ill!il!il !il!ill!il!il!illl ll!il!il!il!il!il!il !il!il!il!il6!iJ66666!iJ66666!iJ!iJ--XXXX--X----X-X----X--XXXX-------X------X--XXXX--------!iJ!illl ll!iJ!il!ill!il!il !iJl!iJ!il!ill!il!il !il!ill!il!il!illl ll!iJ!il!ill!il!il !il!ill!il!ill!il!il !il!ill!il!il!illl ll!il!il!il!il!il!il !il!il!il!il6!iJ66666!iJ66666!il!iJFigure 13-1.Now, if you take a minute to compare the values used for eight withthose used for nine, you should notice that all except two of the values arethe same. So the question naturally arises, "Since nine always followseight, why should I POKE all the values for the nine, when six of them arethe same as before?!?" Funny you should ask!That is the idea behind partial mod ification-alter the existing figureinstead of totally replacing it. Type these lines to change the previouslisting.13 REM14!il POKE 12288,64: POKE 13312 ,6419!il POKE 11264,662!iJ!iJ POKE 12288,66: POKE 13312 ,66Now lines 13© and 14© will POKE only the changes needed to turn theeight into the nine, and similarly lines 19© and 2©© POKE the changesrequired to turn nine into zero. When you run the program you will notsee much difference, but you will have the satisfaction of knowing thatyour code is more efficient.Granted, the time savings is insignificant in this example, but if you aretrying to animate 15© bytes worth of Zylon spaceship, or what have you,partial n1odification could potentially save a great deal of time.Pre-calculationThe next topic to consider is pre-calculation. When a figure is moving
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APPLE IICOMPUTERGRAPHICSKen William
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Contents1 Introduction 12 Computer
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1IntroductionThe level of graphics
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4 APPLE II COMPUTER GRAPHICSmachine
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6 APPLE II COMPUTER GRAPHICScompute
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8 APPLE II COMPUTER GRAPHICSzeros i
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10 APPLE II COMPUTER GRAPHICSthe sy
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•
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14 APPLE II COMPUTER GRAPHICSdiffer
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16 APPLE II COMPUTER GRAPHICSDOS ve
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18 APPLE II COMPUTER GRAPHICSThe po
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4APP LESO FTExtensionsObjectivesAft
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CHAPTER 4-APPLESOFT EXTENSIONS 23va
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CHAPTER 4-APPLESOFT EXTENSIONS 251
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Introducing -Diskette to Accompany
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5Graphics Modes andSoft SwitchesObj
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CHAPTER 5-CRAPHIC MODES AND SOFT SW
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CHAPTER 5-GRAPHIC MODES AND SOFT SW
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CHAPTER 5-CRAPHIC MODES AND SOFT SW
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40 APPLE II COMPUTER GRAPHICSthe le
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42 APPLE II COMPUTER GRAPHICSSoluti
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44 APPLE II COMPUTER GRAPHICSEach b
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..46 APPLE II COMPUTER GRAPHICS[ b
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48 APPLE II COMPUTER GRAPHICS3 PLOT
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50 APPLE II COMPUTER GRAPHICSType t
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52 APPLE II COMPUTER GRAPHICSVocabu
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54 APPLE II COMPUTER GRAPHICScolor.
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60 APPLE II COMPUTER GRAPHICS70 POK
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62 APPLE II COMPUTER GRAPHICS37- 85
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8Hi-Res GraphicsObjectivesAfter rea
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CHAPTER 8-Hl-RES GRAPHICS 67When J
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C..: HAPTER 8-Hl-RES GRAPHICS 69Goi
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CHAPTER 8-Hl-RES GRAPHICS 71Row Add
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CHAPTER 8-Hl-RES GRAPHICS 73The fou
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CHAPTER 8-Hl-RES GRAPHICS 75The row
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CHAPTER 8-Hl-RES GRAPHICS 77Solutio
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CHAPTER 8-Hl-RES GRAPHICS 79b. XX-X
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82 APPLE II COMPUTER GRAPHICSA Bit
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84 -APPLE II COMPUTER GRAPHICSget t
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86 APPLE II COMPUTER GRAPHICSDOTBIT
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88 APPLE II COMPUTER GRAPHICSIn Fig
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90 APPLE II COMPUTER GRAPHICSblue a
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92 APPLE II COMPUTER GRAPHICSHEX HE
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94 APPLE II COMPUTER GRAPHICS50 HGR
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96 APPLE II COMPUTER GRAPHICSone of
Page 107 and 108: 991 111ObjectivesAfter reading Chap
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Page 111 and 112: CHAPTER 10-SHAPING UP 103In the fir
Page 113 and 114: CHAPTER 10-SHAPING UP 105( (J(J) ha
Page 115 and 116: CHAPTER 10-SHAPING UP 107as the com
Page 117 and 118: 6 POKE 232,: POKE 233 ,37 REM8 REM
Page 119 and 120: CHAPTER 10-SHAPING UP 111Sections A
Page 121 and 122: CHAPTE R 10-SHAPING UP 113DRAW 2 AT
Page 123 and 124: CHAPTER 10-SHAPING UP 115printed at
Page 125: CHAPTER 10-SHAPING UP 117Exercises1
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Page 143 and 144: 12Byte-Move ShapesObjectivesAfter r
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Page 149 and 150: CHAPTER 12-BYTE-MOVE SHAPES 141POKE
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Page 189 and 190: GlossaryA particular number that co
Page 191 and 192: GLOSSARY 183HI-RES. High Resolution
Page 193 and 194: GLOSSARY 185SEPARATION. Any one of
Page 195 and 196: Editoi:(s)Hi-Res, 66, 100Low- Res,
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