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DRIVELTR.ASM
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Assembly Source File
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1993-01-04
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1KB
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43 lines
TITLE "Get Current Drive Letter"
PAGE 60,132
.MODEL LARGE
.CODE
;
; compile: masm /mx driveltr;
;
;
; Function: DriveLtr()
; Parameters: None
; Returns: char - The current drive letter
; Author: Mike Taylor
; Date: 16 December 1988
;
; Description: This function call DOS int 21h function 19h to find out the
; current drive letter. Function 19h returns a drive code
; that has this pattern: 0 = A:, 1 = B:, etc.
;
; Called By: Microsoft C large memory model routine
PUBLIC _DriveLtr
_DriveLtr PROC
push bp ; save the caller's base pointer register
mov bp,sp ; establish our stack frame by saving the current
; stack pointer
xor ax,ax ; clear the ax register
mov ah,19h ; set up the call to DOS's Get Current Disk function
int 21h ; ah = function 19h of interrupt 21h
mov ah,0 ; clear out high byte of ax
pop bp ; restore callers base pointer
ret
_DriveLtr ENDP
END