Watch the ZX81 draw a picture.
PROG : 16509
D-FILE: 18017
VARS : 18810
E-LINE: 18811
STKBOT: 18811
STKEND: 18811
9999 means line number
PRINT means treat as KEYWORD P
10 REM *THE PICTURE**SLR/1984*
110 LET X=25
111 LET Y=7
112 LET X1=60
113 LET Y1=Y
114 GOSUB 8050
120 GOSUB 9000
121 LET X1=55
122 LET Y1=4
123 GOSUB 8050
125 GOSUB 9000
126 LET X1=30
127 GOSUB 8050
128 GOSUB 9000
129 LET X1=25
130 LET Y1=6
131 GOSUB 8050
132 LET X=48
133 LET Y=8
134 LET X1=X
135 LET Y1=37
136 GOSUB 8050
137 GOSUB 9000
138 LET X1=45
139 LET Y1=34
140 GOSUB 8050
141 GOSUB 9000
142 LET X1=48
143 LET Y1=34
144 GOSUB 8050
145 LET X=48
146 LET Y=33
147 LET X1=26
148 LET Y1=10
149 GOSUB 8050
150 GOSUB 9000
151 LET X1=59
152 LET Y1=10
153 GOSUB 8050
154 GOSUB 9000
155 LET X1=48
156 LET Y1=33
157 GOSUB 8050
158 LET X=0
159 LET Y=23
160 LET X1=37
161 LET Y1=Y
162 GOSUB 8050
163 LET X=53
164 LET X1=63
165 GOSUB 8050
166 LET X=4
167 LET Y=41
168 LET X1=8
169 LET Y1=Y
170 GOSUB 8050
171 GOSUB 9000
172 LET X1=10
173 LET Y1=40
174 GOSUB 8050
175 GOSUB 9000
176 LET Y1=39
177 GOSUB 8050
178 GOSUB 9000
179 LET X1=8
180 LET Y1=37
181 GOSUB 8050
182 GOSUB 9000
183 LET X1=4
184 GOSUB 8050
185 GOSUB 9000
186 LET X1=2
187 LET Y1=38
188 GOSUB 8050
189 GOSUB 9000
190 LET Y1=39
200 GOSUB 8050
201 GOSUB 9000
202 LET X1=4
203 LET Y1=40
204 GOSUB 8050
205 PAUSE 1000
206 RUN
500 SAVE "PICTURE"
510 RUN
8050 LET A=X-X1
8060 LET B=Y-Y1
8070 LET C=(A AND ABS A>=ABS B)+
(B AND ABS B>=ABS A)
8080 IF C=0 THEN LET C=.1
8090 FOR F=0 TO C STEP SGN C
8100 PLOT X+A/C*-F,Y+B/C*-F
8110 NEXT F
8120 RETURN
9000 LET X=X1
9010 LET Y=Y1
9020 RETURN