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Ahoy 1985 November
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Ahoy_Magazine_85-11_1985_Double_L.d64
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blackboard.bas
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.txt
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Commodore BASIC
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2022-10-26
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777b
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26 lines
10 rem *** "blackboard.bas" *******
20 base=2*4096:poke 53272,peek(53272)or8:rem put high-res map at 8192
30 poke 53265,peek(53265)or32:rem enter high-res bit-map mode
40 for i=base to base+7999:poke i,0:next:rem clear bit map
50 for i=1024 to 2023:poke i,16:next i:rem black background, white line
60 goto 200
80 rem ****** plot routine **********
90 char=int(hpsn/8)
100 row=int(vpsn/8)
110 line=vpsn and 7
120 byte=base+row*320+8*char+line
130 bit=7-(hpsn and 7)
140 poke byte,peek(byte) or (2^bit)
150 return
200 rem **** draw vertical line *******
220 for vpsn=0 to 199:rem plot line from top to bottom of screen
225 for hpsn=159 to 160
230 gosub 80
240 next hpsn:next vpsn
245 rem *** draw horizontal line ******
250 vpsn=100:rem halfway down screen
260 for hpsn=0 to 319:rem plot line from left side to right side of screen
270 gosub 80
280 next hpsn
290 goto 290