name    free        page    60,132        title   'FREE --- Report free space on disk'; FREE --- a utility to report free space on;          the default or selected disk drive.; ; Requires PC-DOS or MS-DOS 2.0.;; Used in the form:; A> FREE  [unit:] ; (item in square brackets is optional);; version 1.0   July 4, 1984 ; Copyright (c) 1984 by Ray Duncan; May be freely reproduced for non-commercial use. cr      equ     0dh             ;ASCII carriage returnlf      equ     0ah             ;ASCII line feedblank equ 20h  ;ASCII space codeeom equ '$'  ;end of string marker; Here we define a dummy segment containing labels; for the default file control block and the command tail buffer,; so that the main program can access those locations.;psp segment para public 'PSP'   org 05chfcb label byte  ;default file control block org 080hcommand label byte  ;default command bufferpsp endscseg segment para public 'CODE' assume cs:cseg,ds:psp,es:data,ss:stackget_drive proc near  ;get drive selection, if any,    ;otherwise obtain the identity    ;of the current disk drive.    ;Return drive (1=A, 2=B, etc) in AL.    ; mov  al,fcb         ;Pick up the drive code, parsed     ;by DOS into the default file    ;control block. or al,al  ;Is it the default? jnz get_drive1 ;no, use it mov ah,19h  ;Yes, get the actual current int 21h  ;drive from PC-DOS. inc  al  ;Increment to match FCB code.get_drive1:   ;Return drive code in AL. retget_drive endpfree  proc    far             ;entry point from PC-DOS        push    ds              ;save DS:0000 for final        xor     ax,ax           ;return to PC-DOS        push    ax        mov     ax,data         ;make our data segment        mov     es,ax           ;addressable via ES register.        mov     ah,30h  ;check version of PC-DOS.         int     21h        cmp     al,2        jae     free1  ;proceed, DOS 2.0 or greater.        mov     dx,offset msg2  ;DOS 1.x --- print error message mov ax,es  ;and exit. First fix up DS register  mov ds,ax  ;so error message is addressable. jmp free4free1:  call    get_drive  ;get drive selection into DL. push es  ;copy ES to DS for remainder pop ds  ;of the program... assume ds:data  ;and tell assembler about it. mov dl,al   add al,'A'-1 ;form drive letter from drive code, mov outputb,al ;and put it into the output string.  mov ah,36h  ;now call DOS to get free disk space. int 21h cmp ax,-1  ;was drive invalid? je free3  ;yes,go print error message    ;drive was ok, so now registers are...    ;AX=number of sectors per cluster    ;BX=available clusters,    ;CX=number of bytes per sector,    ;DX=total clusters per drive.    ;calculate free space: mul cx  ;sectors per cluster * bytes per sector    ;(we assume this won't overflow into DX) mul bx  ;then * available clusters     ;DX:AX now contains free space in bytes.    ;SI = last byte address for converted string. mov si,offset (outputa+9) mov cx,10  ;CX = 10, radix for conversion call bin_to_asc ;convert free space value to ASCII, mov dx,offset output jmp free4  ;and print it out.free3:  mov     dx,offset msg1  ;illegal drive, print errorfree4: mov ah,9  ;print the string whose address int 21h  ;is in DX. ret   ;then return to DOS.free   endp; Convert 32 bit binary value to ASCII string.;; Call with  DX:AX = signed 32 bit value;      CX    = radix;            SI    = last byte of area to store resulting string;              (make sure enough room is available to store;        the string in the radix you have selected.);; Destroys AX, BX, CX, DX, and SI.;bin_to_asc proc near  ;convert DX:AX to ASCII.    ;force storage of at least 1 digit. mov byte ptr [si],'0'  or dx,dx  ;test sign of 32 bit value, pushf   ;and save sign on stack. jns bin1  ;jump if it was positive. not dx  ;it was negative, take 2's complement not ax  ;of the value.  add ax,1 adc dx,0bin1:    ;divide the 32 bit value by the radix     ;to extract the next digit for the    ;forming string. mov bx,ax  ;is the value zero yet? or bx,dx jz bin3  ;yes, we are done converting. call divide  ;no, divide by radix. add bl,'0'  ;convert the remainder to an ASCII digit. cmp bl,'9'  ;we might be converting to hex ASCII, jle bin2  ;jump if in range 0-9, add bl,'A'-'9'-1 ;correct it if in range A-F.bin2: mov [si],bl  ;store this character into string. dec si  ;back up through string, jmp bin1  ;and do it again.bin3:    ;restore sign flag, popf   ;was original value negative? jns bin4  ;no, jump    ;yes,store sign into output string. mov byte ptr [si],'-'bin4: ret   ;back to caller.bin_to_asc endp; General purpose 32 bit by 16 bit unsigned divide.; This must be used instead of the plain machine unsigned divide; for cases where the quotient may overflow 16 bits (for example,; dividing 100,000 by 2).  If called with a zero divisor, this; routine returns the dividend unchanged and gives no warning.;; Call with DX:AX = 32 bit dividend;           CX    = divisor;; Returns   DX:AX = quotient;           BX    = remainder;     CX    = divisor (unchanged);divide proc near  ; Divide DX:AX by CX jcxz div1  ; exit if divide by zero push ax  ; 0:dividend_upper/divisor mov ax,dx xor dx,dx div cx mov bx,ax  ; BX = quotient1 pop ax  ; remainder1:dividend_lower/divisor div cx xchg bx,dx  ; DX:AX = quotient1:quotient2div1: ret   ; BX = remainder2divide endpcseg    endsdata    segment para public 'DATA'output  db cr,lfoutputa  db 10 dup (blank)  db ' bytes free on drive 'outputb  db 'x:',cr,lf,eommsg1            db      cr,lf                db      'That disk drive does not exist.'                db      cr,lf,eommsg2            db      cr,lf                db      'Requires DOS version 2 or greater.'                db      cr,lf,eomdata    ends    stack   segment para stack 'STACK'        db      64 dup (?)stack   ends        end     free