Sinclair ZX80 / ZX81 / Z88 Forums

This program checks how much memory (RAM) is present (with or without the memory expansion):

1 POKE 18000, 33
2 POKE 18001, 11
3 POKE 18002, 0
4 POKE 18003, 57
5 POKE 18004, 68
6 POKE 18005, 77
7 POKE 18006, 201
8 PRINT (USR(18000) - 16373) / 1024; "K"

10 CLS
20 PLOT RND*60, RND*40
30 UNPLOT RND*60, RND*40
40 GOTO 10

The above works with the ZX81 only. My mistake: the ZX80 only supports integers, and to create a circle, you must work with decimal numbers.

Try this and let us know how it goes:

10 FOR ANGLE = 0 TO 360 STEP 5
20 LET X = RND * 10 * SIN(ANGLE)
30 LET Y = RND * 10 * COS(ANGLE)
40 PLOT 96 + INT(X), 48 + INT(Y)
50 NEXT ANGLE

10 CLS
20 FOR X=INT(RND*64) TO 62
30 FOR Y=INT(RND*44) TO 42
40 PLOT X,Y
50 NEXT Y
60 NEXT X
70 GOTO 10