Category : C++ Source Code
Archive   : VCCRT2.ZIP
Filename : PUTCH.ASM

page ,132
title putch - write a character to standard output
;***
;putch.asm - contains putch() for DOS 3 (write char to console)
;
; Copyright (c) 1987-1992, Microsoft Corporation. All Rights Reserved.
;
;Purpose:
; The routine "putch()" writes a single character to standard output.
;
;
;*******************************************************************************

include version.inc
.xlist
include cmacros.inc
include msdos.inc
include defsegs.inc
.list


ifndef _WINDOWS
_DEBUGSCREEN equ 1 ; debug screen swapping
endif


ifdef _DEBUGSCREEN
CrtDefSegs

sBegin dbdata ;
assumes ds,data ; Used to do the running under
externW __aDBswpflg ; a debugger screen swapping
externW __aDBswpchk ;
sEnd dbdata ;
extrn __aDBdoswp:ABS ;
endif ; _DEBUGSCREEN

sBegin code

assumes cs,code

page
;***
;int _putch(c) - write one character to standard output (usually the console)
;
;Purpose:
; Calls INT 21H Function 6, to output the character
;
;Entry:

; int c - Character to be output
;
;Exit:
; AL = character that was output, AH = 0
;
;Uses:
; DX
;
;Exceptions:
;
;*******************************************************************************

cProc _putch,,<>

parmb byt

cBegin
mov dl,[byt] ; character to output
mov ah,6h
ifdef _DEBUGSCREEN
cmp __aDBswpflg,__aDBdoswp ; Aware debugger as parent?
jne @F ; No -- skip
mov bx,-1
call __aDBswpchk ; Yes -- see if we need to swap screens
@@:
endif ; _DEBUGSCREEN
callos
xchg ax,dx ; mov al,[byt]
mov ah,0
pop bp
ret
cEnd

sEnd

end