Path: utzoo!attcan!uunet!tektronix!percival!bucket!leonard
From: leonard@bucket.UUCP (Leonard Erickson)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Strange happening with INT 21, AH=4EH
Message-ID: <1230@bucket.UUCP>
Date: 22 Jan 89 21:04:17 GMT
References: <13338@ncoast.UUCP>
Reply-To: leonard@bucket.UUCP (Leonard Erickson)
Distribution: na
Organization: Rick's Home Grown Unix; Portland, OR
Lines: 35

In article <13338@ncoast.UUCP> allbery@ncoast.UUCP (Brandon S. Allbery) writes:
<In designing an "ls" program for myself, I've been playing with the INT 21
<function 4E/4F (find first/next match file).  Just for laughs, I tried
<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).
<
<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)?

As far as DOS is concerned, you have the following devices, which may
be treated as files:
CON	stdin/stdout
AUX	alias for the first com port
PRN	stdprn (usually LPT1)
LPT1	1st paralell port
LPT2	2nd parallel port
LPT3	3rd ....
COM1	1st com port
COM2	2nd com port
COM3	3rd ...
COM4	4th ...
NUL	null device

All of these may have \ or \DEV\ in front of them.
-- 
Leonard Erickson		...!tektronix!reed!percival!bucket!leonard
CIS: [70465,203]
"I used to be a hacker. Now I'm a 'microcomputer specialist'.
You know... I'd rather be a hacker."