APPENDIX TWELVE



787            313            TEMP2
     One-byte temporary storage register.

788            314            PTIMOT
     Moved from 28 ($1C) in the 400/800. Same initial value (30).

829-831        33D-33F        PUPBT1-3
     Power-up and reset validation registers 1-3. Used on warm start
     to verify the integrity of memory. The OS initializes these loca-
     tions to 92 ($5C), 147 ($93), and 37 ($25), respectively. When RE-
     SET is pressed, these bytes are checked, and it they are the
     same as initialized, a warm start is done; otherwise, a cold start
     occurs.

838,839        346,347        IOCB0
     To send your output to the printer, POKE 838,202 and POKE
     839,254. To turn off the printer and send everything back to the
     screen, POKE 838,175 and POKE 839,242. This program from
     Matt Ratcliff allows you to toggle output between printer and
     screen by pressing SELECT (it works equally well on the
     400/800):

     10 DIM A$(1):CONSOL=53279:GRAPHICS 0:IOCB0E
        =838
     20 PHDLR=58422
     30 EHDLR=58374
     40 PL=PEEK(PHDLR):PH=PEEK(PHDLR+1)
     50 EL=PEEK(EHDLR):EH=PEEK(EHDLR+1)
     60 PRINT "Text will print continuously."
     70 PRINT "Press SELECT to toggle output"
     80 PRINT "between printer and screen.":?
     90 PRINT "Get printer ready and press RETUR
        N"
     100 INPUT A$:I=1:DIR=0
     110 PRINT I;" Press select to change output
         .":I=I+1
     120 IF PEEK(CONSOL)<>5 THEN 110
     130 IF DIR THEN POKE IOCB0E,EL:POKE IOCB0E+
         1,EH
     140 IF NOT DIR THEN POKE IOCB0E,PL:POKE IO
         CB0E+1,PH
     150 DIR= NOT DIR
     160 IF PEEK(CONSOL)<>7 THEN 160
     170 GOTO 110

1000           3E8            SUPERF
     Screen editor register; cleared on entry to the "put byte" rou-
     tine, the editor changes keycodes 142-145 ($8E-$91) to 28-31
     ($1C-$1F; see 121; $79) and sets SUPERF to nonzero.