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15EF: THE 'MAIN PRINTING' SUBROUTINE
Used by the routines at MAIN_EXEC, OUT_SP_2, OUT_NUM_1 and PRINT_FP.
Input
A Value from +00 to +09 (for digits) or +11 to +22 (for the letters A-R)
Output
OUT_CODE 15EF LD E,$30 Increase the value in the A register by +30.
15F1 ADD A,E
This entry point is used by the routine at PRINT_A_1 with A holding the code of the character to be printed.
PRINT_A_2 15F2 EXX Save the registers.
15F3 PUSH HL
15F4 LD HL,($5C51) Fetch the base address for the current channel (CURCHL). This will point to an output address.
This entry point is used by the routine at INPUT_AD with A holding the code of the character to be printed.
Now call the actual subroutine. HL points to the output or the input address as directed.
CALL_SUB 15F7 LD E,(HL) Fetch the low byte.
15F8 INC HL Fetch the high byte.
15F9 LD D,(HL)
15FA EX DE,HL Move the address to the HL register pair.
15FB CALL CALL_JUMP Call the actual subroutine.
15FE POP HL Restore the registers.
15FF EXX
1600 RET Return will be from here unless an error occurred.
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