GSREAD

Read character from string

Specification

6502	On entry:	On exit:
C	undefined	0=Character valid 1=End of string reached
?&F2	LSB of start of array	preserved
?&F3	MSB of start of array	preserved
A	undefined	Next character of string; =&0D if end of string reached
Y	Offset of current character	Offset of next character

Returns a character from a string found using GSINIT. The string may be enclosed in double quotes (") in which case spaces in the string are preserved. The string may also contain control codes and high-order characters encoded with an escape sequence.

GSREAD parses the character sequence at the position given by (?&F2,?&F3)+Y and scans forward.

If the string began with " then a character is returned unless the closing " is reached; then C=1 and A=&0D is returned. CR encountered before the closing " causes error &FD, Bad string.

Otherwise a character is returned unless CR or space (if C=0 to GSINIT), or CR only (if C=1 to GSINIT) is reached; then C=1 and A=&0D.

(?&F2,?&F3)+Y points to the next character unless C=1, in which case GSREAD skips any spaces following the end of the string.

Note

The character returned by GSINIT is not necessarily the character returned by the first call to GSREAD.

Entry points

• 6502 Entry Address: &FFC5 (I/O processor only)

Regregex (talk) 18:31, 11 January 2019 (CET)