ZX81 Programs


Read about, play, run, or list games, animations, and more. These are my programs from the ’80s to today.

ZX81 Program Listing

collatz (collatz.p)


SYSTEM VARIABLES

PROG  : 16509
D-FILE: 17088
VARS  : 17881
E-LINE: 17882
STKBOT: 17882
STKEND: 17882


LEGEND

9999 means line number
PRINT means treat as KEYWORD P


PROGRAM LISTING

  10 REM *COLLATZ-CNJT*SLR/2024*
  20 LET N=INT (RND*99999999+1)
  30 LET I=0
  40 SCROLL
  50 PRINT TAB 7;"COLLATZ CONJEC
TURE"
  60 SCROLL
  70 PRINT TAB 7;"óóóóóóóóóóóóóó
óóóó"
  80 SCROLL
  90 LET I=I+1
 100 LET N$=STR$ N
 110 PRINT TAB 16-LEN N$/2;N$
 120 SCROLL
 130 PRINT TAB 16;":"
 140 LET O=INT (INT (N/2)-N/2)
 150 LET C=(N/2 AND NOT O)+((3*N
+1) AND O)
 160 LET N=C
 170 IF N=1 THEN GOTO 190
 180 GOTO 80
 190 SCROLL
 200 PRINT TAB 16;N
 210 SCROLL
 220 SCROLL
 230 LET N$="DONE IN "+STR$ I+" 
ITERATIONS/"
 240 PRINT TAB 16-LEN N$/2;N$
 250 PAUSE 800
 260 SCROLL
 270 SCROLL
 280 PRINT TAB 8;"STARTING OVER.
.."
 290 SCROLL
 300 SCROLL
 310 RUN
 320 SAVE "COLLATZ"
 330 RUN