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

page ,132
title setdrive - contains the _dos_setdrive() function
;***
;setdrive.asm - contains _dos_setdrive()
;
; Copyright (c) 1987-1992, Microsoft Corporation. All rights reserved.
;
;Purpose:
; This module contains the _dos_setdrive() function.
;
;*******************************************************************************

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

sBegin code

assumes cs,code

page
;***
;unsigned _dos_setdrive(drive, p_ndrive) - change default drive (1=A:, 2=B:, etc.)
;
;Purpose:
; The function "_dos_setdrive" allows the user to change
; the current default drive, via INT 21H function 0EH.
; It also returns the number of valid drives in the system.
;
; NOTE: INT 21h Function 19h accepts (0=A:, 1=B:, etc.) but
; _dos_setdrive() uses values (1=A:, 2=B:, etc.) consistent
; with other DOS functions.
;
;Entry:
; unsigned drive; drive to be the default
; unsigned * p_ndrives; address to store drive
;
;Exit:
;
;Uses:
;
;Exceptions:
;
;*******************************************************************************

cProc _dos_setdrive,,<>

parmB _drive ; drive to be default drive
parmDP _p_ndrives ; address to store number of valid drives

cBegin

mov dl,(_drive)
dec dx
callos selectdisk ; set current drive

mov ah,0
if sizeD
les bx,(_p_ndrives)
mov es:[bx],ax
else
mov bx,(_p_ndrives)
mov [bx],ax
endif
xor ax,ax ; Do NOT return something useful --

ifdef _WINDOWS
cEnd
else
pop bp
ret
cEnd
endif


sEnd

end