Category : BASIC Source Code
Archive   : EXECSRCE.ZIP
Filename : DSK.ASM

PAGE 60,132 ;
TITLE BASIC SUBROUTINE : DSK(A,B)
.RADIX 16
;BASIC machine lang. subroutine: CALL DSK(A,B)
;A=Drive to check- 0,1,2 or 3. 0=default drv, 1=A:, etc.
;B=# of free sectors (returned).
;Jack Wright Nov 1983
CSEG SEGMENT PARA PUBLIC 'CODE'
ASSUME CS:CSEG
PUBLIC DSK
;DS=ES=SS=default DEF SEG (BASIC's data segment)
;All seg. regs. & SP must be saved & restored.
;BIOS interrupts preserve all seg. regs. & BX,CX,DX.
;DOS 2.0
ORG 100
DSK PROC FAR
PUSH BP
MOV BP,SP
MOV SI,[BP+08] ;Addr. of arg. A->SI.
MOV DX,[SI] ;A->DX (A=drive # to check)
CLI ;Disable maskable interrupts
MOV AX,CS
MOV SS,AX ;Set up new stack for INT 21 s
MOV SP,100
STI
MOV AH,36 ;DL=drive to check
INT 21 ;Returns AX=# of sectors/alloc. unit,
MUL BX ;BX=# of avail. alloc. units
;after MUL, DX,AX=no. of avail. sectors
CLI
MOV BX,ES ;SS was saved in ES
MOV SS,BX
MOV SP,BP ;SP was saved in BP
STI
;Must restore SS (above) before checking [BP+06] (below):
MOV DI,[BP+06] ;Point DI to B
MOV [DI],AX ;Transfer AX to last arg. (B)
EXIT: POP BP
RET 4
DSK ENDP
CSEG ENDS
END DSK ;