Int 21/AH=37h

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DOS 2.x and 3.3+ only - AVAILDEV - SPECIFY \DEV\ PREFIX USE

AH = 37h
AL = subfunction
02h get availdev flag

Return:
DL = 00h \DEV\ must precede character device names = nonzero \DEV\ is optional 03h set availdev flag DL = new state 00h \DEV\ is mandatory nonzero \DEV\ is optional

Return:
AL = status 00h successful FFh unsupported subfunction

Notes: All versions of DOS from 2.00 allow \DEV\ to be prepended to device names without generating an error even if the directory \DEV does not actually exist (other paths generate an error if they do not exist); DOS 2.x has an AVAILDEV= option in CONFIG.SYS to make \DEV mandatory. Although MS-DOS 3.3+, DR DOS 3.41+, and Novell DOS 7 accept these calls, they have no effect, and AL=02h always returns DL=FFh (except for Novell DOS 7, which leaves AX unchanged for both subfunctions)

Category: DOS Kernel - Int 21h - D

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