Note: This API call is for DOS personality only. Use Family API for portability.

2018/09/07 07:04 · prokushev

Int 21H, AH=37H, AL=00H


2 and higher



Family API


      AX = 3700h


AL = status

          00h successful
              DL = current switch character
          FFh unsupported subfunction



Determine the character which is used to introduce command switches.
        This setting is ignored by MS-DOS commands in version 4.0 and higher,
        but is honored by many third-party programs and by Novell DOS 7
        external commands

BUG: Novell DOS 7's COMMAND.COM (prior to Update 15) fails to honor the

       SwitChar setting for internal commands even though COMMAND.COM
        honors it in its own command tail (i.e. COMMAND /?); even in Update
        15, internal commands fail to honor SwitChar for the /? help option
documented in some OEM versions of some releases of DOS
      supported by OS/2 compatibility box
      always returns AL=00h/DL=2Fh for MS-DOS 5+ and DR DOS 3.41-6.0
      Novell DOS 7 COMMAND.COM indicates switch characters other than '/'
        by changing the first backslash (and only the first one) in the
        path it prints for PROMPT $p with a forward slash

See also



Process manager INT 20H, INT 21H: 00H, 25H, 26H, 31H, 34H, 35H, 4CH, INT 22H, INT 27H, INT 28H
File manager INT 25H, INT 26H, INT 21H: 0DH, 0EH, 0FH, 10H, 11H, 12H, 13H, 14H, 15H, 16H, 17H, 19H, 1AH, 1BH, 1CH, 21H, 22H, 23H, 24H, 27H, 28H, 29H, 2EH, 2FH, 32H, 3305H, 36H
Character Device I/O INT 29H, INT 21H: 01H, 02H, 03H, 04H, 05H, 06H, 07H, 08H, 09H, 0AH, 0BH, 0AH, 0CH
Signals INT 23H, INT 24H, INT 21H: 3300H, 3301H, 3302H
Memory manager
Date and Time INT 21H: 2AH, 2BH, 2CH, 2DH
Misc INT 21H: 30H, 3306H, 3700H, 3701H, 3702H, 3703H
NLS INT 21H: 3303H, 3304H
2018/09/04 19:23 · prokushev

en/docs/dos/api/int21/37/00.txt · Last modified: 2020/12/14 10:57 by prokushev