INT 29H: Fast PUTCHAR
Compatibility: ◄Undoc► ??
Expects: AL character to display
Returns: ?? undocumented
Info: This is ◄undocumented► through DOS 6.0 and I can't find much
INT 29H outputs a character to the screen. When ANSI.SYS is
resident, it intercepts this vector; otherwise, it is handled
internally by DOS.
My disassembly shows that the routine fetches the current screen
color into BL and then passes AL on to INT 10H 09H (write
character). It updates the cursor position. It also appears to
take special action on:
07H BEL (make a beep; don't update cursor)
08H BS (backspace; cursor backwards one column)
0aH LF (line feed; cursor to next line; scroll if needed)
0dH CR (carriage return; cursor to start of line)
1bH ESC (ANSI Escape Sequences)
This fn is NOT particularly fast, compared to hand-optimized
writes directly to video memory. In fact, I can see no
advantage over using, say INT 10H 0eH. However, it is a bit
faster than handle-oriented file output to the CON device.
See Also: Character I/O Functions
INT 2fH 1a00H (is ANSI installed?)
ANSI Escape Sequences