求Commodore 8032/BASIC4的字符串输出子程序（类似C64的$AB1E）

Great question! The Commodore 8032 (a PET-series machine running BASIC 4.0) has ROM-based string output routines that mirror the C64's $AB1E functionality, though the addresses and exact behavior have small differences. Here's what you need to know:

Key String Output Subroutine for 8032 #

The closest ROM routine to the C64's $AB1E on the 8032 is $BDCD. This is the standard null-terminated string printer, with these details:

• Call Method: Load the low byte of your string's starting address into the accumulator (A), and the high byte into the Y register (Y). Then run JSR $BDCD.
• Termination Rule: The routine prints characters from the specified address until it hits a null byte ($00). Unlike the C64's $AB1E, it doesn't recognize a quote character (", $22) as a stop signal—only $00 terminates the output.

Example Assembly Code #

If you have a null-terminated string stored at $0200 (e.g., $0200: "HELLO WORLD" $00), here's how to trigger the output:

LDY #$02    ; Load high byte of string address into Y
LDA #$00    ; Load low byte of string address into A
JSR $BDCD   ; Execute string output routine

Handling Quote-Terminated Strings (If Needed) #

Since $BDCD only stops at $00, you can wrap the 8032's known character output routine ($FFD2) in a small loop to replicate the C64's dual-terminator behavior:

; Assume string start address is stored in ($00,$01) (low/high bytes)
LDX #$00
PRINT_LOOP:
LDA ($00,X) ; Load next character from string
BEQ END_PRINT ; Exit if null byte is found
CMP #$22    ; Check if current character is a quote
BEQ END_PRINT ; Exit if quote is found
JSR $FFD2   ; Print the current character
INX
BNE PRINT_LOOP
END_PRINT:

Memory Map Note #

The 8032's ROM lives in the $C000-$FFFF range, so addresses like $BDCD are fixed in the machine's standard BASIC 4.0 ROM and won't vary across regular 8032 units.

内容的提问来源于stack exchange，提问作者John G