NOMON C,I,O

 63800  REM  BLOCK LISTER
 63805  VTAB 22: HTAB 1: CALL  - 958
 63810  INPUT "BLOCK#=";BLOCK$
 63815  IF BLOCK$ = "" THEN  END 
 63820 BLOCK =  INT ( VAL (BLOCK$))
 63825  IF (BLOCK < 0) OR (BLOCK > 639) THEN 63805
 63830 X = 100 * BLOCK:Y = X + 99
 63835  HOME : GOSUB 63900: CALL  - 912
 63840  GOTO 63805
 63900  REM  LIST X-Y
 63905 ADRS =  PEEK (121) + 256 *  PEEK (122) + 144
 63910  FOR I = 4 TO 0 STEP  - 1
 63915  POKE ADRS + I,X - 10 *  INT (X / 10) + 48
 63920 X =  INT (X / 10)
 63925  POKE ADRS + I + 6,Y - 10 *  INT (Y / 10) + 48
 63930 Y =  INT (Y / 10)
 63935  NEXT I
 63940  LIST XXXXX - YYYYY
 63945  RETURN 
GOTO 63800