Path: utzoo!utgpu!attcan!uunet!lll-winken!ames!mailrus!tut.cis.ohio-state.edu!rutgers!bellcore!texbell!killer!dono
From: dono@killer.DALLAS.TX.US (Don OConnell)
Newsgroups: comp.sys.ibm.pc
Subject: Re:...INT 21 ...
Keywords: INT 21
Message-ID: <6798@killer.DALLAS.TX.US>
Date: 15 Jan 89 10:45:04 GMT
Organization: The Unix(R) Connection, Dallas, Texas
Lines: 61


>From allbery@ncoast.UUCP Sat Jan 14 23:28:32 1989
>invoking it on the pathname \DEV\CON -- and, to my surprise, it returned
>with an attribute byte of 40H!  In playing with it, I discovered that
>\DEV\CON was the *only* device that produced this behavior; other devices,
>and \DEV\*.*, returned AX=3 (path not found).
               SHOULD BE 2-^
>This was done in a Turbo Pascal 3.01 program running under MS-DOS 3.21.

>Anyone know if I hit a fluke or if this actually happens?  Does it have to
>do with the device being open by the program (i.e. \DEV\CON is
>stdin/stdout/stderr -- but then, \DEV\CON1 should be open as stdaux and
>\DEV\LPT1 as stdprn)?

Yes DOS does have some /dev files, though they are not the standard UNIX 
names, ie.:
	/dev/con	console
	/dev/prn	printer
	/dev/com?	communications dev [1/2]
    I don't know about /dev/con1 but I doubt that it exists. Nor do I know 
    what stdaux would be called.

>From allbery@ncoast.UUCP Sat Jan 14 23:34:04 1989
>
>The only copy of the Interrupt List I can find on ncoast and my almost
>useless DOS manual agree that the structureset by INT 21, AH=4EH/4FH
>contains one 16-bit entity each for file date and time.  Question:  does
>anyone know the format of these numbers?

INT 21 - DOS 2+ - FIND FIRST ASCIZ (FIND FIRST)
        AH = 4Eh
        CX = search attributes
        DS:DX -> ASCIZ filename
Return: CF set on error
            AX = error code
        [DTA] = data block
              undocumented fields
                  PC-DOS 3.10
                     byte  00h:     drive letter
                     bytes 01h-0Bh: search template
                     byte  0Ch:     search attributes
                  DOS 2.x (and DOS 3.x except 3.1???)
                     byte  00h:     search attributes
                     byte  01h:     drive letter
                     bytes 02h-0Ch: search template
                  bytes 0Dh-0Eh: entry count within directory
                  bytes 0Fh-12h: reserved
                  bytes 13h-14h: cluster number of parent directory
              byte  15h:     attribute of file found
              bytes 16h-17h: file time
              bytes 18h-19h: file date
              bytes 1Ah-1Dh: file size
              bytes 1Eh-3Ah: ASCIZ filename+extension
--------------------------------------------------
INT 21 - DOS 2+ - FIND NEXT ASCIZ (FIND NEXT)
        AH = 4Fh
        [DTA] = data block from last AH = 4Eh/4Fh call
Return: CF set on error
            AX = error code
        [DTA] = data block, see AH = 4Eh above
--------------------------------------------------