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    {===========================================================================
    Date: 10-03-93 (00:14)
    From: BRIAN PAPE
    Subj: disk ready
    ---------------------------------------------------------------------------
    Does anyone know if there is any better (and FASTER!) way to tell if a
    disk drive is ready?  I wrote a function yesterday to do that by calling
    the BIOS Read Track interrupt.  The only problem is that it has to
    actually read from the disk, and it is rather slow, especially on slower
    computers.

    Here is my code: }

    { NOTE :

              Added a BOOLEAN function and added Reset DRIVE  GDAVIS 10/15/93}

    USES CRT;

    VAR
       Buf : ARRAY[0..512] OF BYTE;  { Buffer MUST be outside }

    function diskstatus(drive:byte):byte; assembler;  { drive is A=0, B=1 etc}
    asm
      cmp  drive,26
      jb   @driveok
      mov  drive,0   { if drive isn't between 0 and 25, make it 0 (for A:) }
      @driveok:

      mov  ax, seg buf
      mov  es, ax
      mov  bx, offset buf

      mov  ah, 02      { read disk sectors }
      mov  al, 1       { number of sectors to transfer }
      mov  ch, 1       { track number }
      mov  cl, 1       { sector number }
      mov  dh, 1       { head number }
      mov  dl, drive   { drive number (0=A, 3=C, or 80h=C, 81h=D) }
      int  13h

      mov  bl,0    { assume drive is ready }
      jnc  @done   { carry set if unsuccessfull (i.e. disk is not ready) }
      mov  bl,ah
      jmp  @done

      { take out the above two lines to make this just check
        for disk ready/not ready }

      and  ah,$80
      jz   @done   { error was something other than disk not ready }
      mov  bl,false{ disk wasn't ready. store result }
      @done:

      mov  ax,$0000  { reset drive }
      INT  13H

      xor  ax,ax   { shut off disk drive quickly }
      mov  es,ax
      mov  ax,440h
      mov  di,ax
      mov  byte ptr es:[di],01h

      mov  al,bl   { retrieve result }
    end;  { diskstatus }

    function diskready(drive:CHAR):BOOLEAN; assembler;
    asm
      cmp  drive,'a'
      jb   @isupcase  { make it UPPER case }
      sub  drive,20H
      @isupcase:
      cmp  drive,'Z'
      jb   @driveok
      mov  drive,'A'  { if drive isn't between 'A' and 'Z', make it A) }
      @driveok:
      mov  ax, seg buf
      mov  es, ax
      mov  bx, offset buf

      mov  ah, 02  { read disk sectors }
      mov  al, 1   { number of sectors to transfer }
      mov  ch, 1   { track number }
      mov  cl, 1   { sector number }
      mov  dh, 1   { head number }

      mov        dl, drive
      sub        dl, 'A'     { subtract ORD of 'A' }

      {mov  dl, drive   { drive number (0=A, 3=C, or 80h=C, 81h=D) }
      int  13h

      mov  bl,true { assume drive is ready }
      and  ah,$80
      jz   @done   { error was something other than disk not ready }
      mov  bl,false{ disk wasn't ready. store result }
      @done:

      mov  ax,$0000  { reset drive }
      INT  13H

      xor  ax,ax   { shut off disk drive quickly }
      mov  es,ax
      mov  ax,440h
      mov  di,ax
      mov  byte ptr es:[di],01h

      mov  al,bl   { retrieve result }
    end;  { diskready }

    BEGIN
    ClrScr;
    WriteLn(DiskStatus(0));
    WriteLn(DiskReady('a'));  { case ain't significant }
    readkey;
    END.

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