55 lines
1.5 KiB
QBasic
55 lines
1.5 KiB
QBasic
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' Values for keys on the numeric keypad and the spacebar:
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CONST UP = 72, DOWN = 80, LFT = 75, RGHT = 77
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CONST UPLFT = 71, UPRGHT = 73, DOWNLFT = 79, DOWNRGHT = 81
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CONST SPACEBAR = " "
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' Null$ is the first character of the two-character INKEY$
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' value returned for direction keys such as UP and DOWN:
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Null$ = CHR$(0)
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' Plot$ = "" means draw lines; Plot$ = "B" means move
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' graphics cursor, but don't draw lines:
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Plot$ = ""
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PRINT "Use the cursor movement keys to draw lines."
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PRINT "Press the spacebar to toggle line drawing on and off."
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PRINT "Press <ENTER> to begin. Press q to end the program."
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DO: LOOP WHILE INKEY$ = ""
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SCREEN 1
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CLS
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DO
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SELECT CASE KeyVal$
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CASE Null$ + CHR$(UP)
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DRAW Plot$ + "C1 U2"
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CASE Null$ + CHR$(DOWN)
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DRAW Plot$ + "C1 D2"
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CASE Null$ + CHR$(LFT)
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DRAW Plot$ + "C2 L2"
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CASE Null$ + CHR$(RGHT)
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DRAW Plot$ + "C2 R2"
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CASE Null$ + CHR$(UPLFT)
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DRAW Plot$ + "C3 H2"
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CASE Null$ + CHR$(UPRGHT)
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DRAW Plot$ + "C3 E2"
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CASE Null$ + CHR$(DOWNLFT)
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DRAW Plot$ + "C3 G2"
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CASE Null$ + CHR$(DOWNRGHT)
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DRAW Plot$ + "C3 F2"
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CASE SPACEBAR
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IF Plot$ = "" THEN Plot$ = "B " ELSE Plot$ = ""
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CASE ELSE
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' The user pressed some key other than one of the
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' direction keys, the spacebar, or "q", so
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' don't do anything.
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END SELECT
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KeyVal$ = INKEY$
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LOOP UNTIL KeyVal$ = "q"
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SCREEN 0, 0
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WIDTH 80
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END
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