Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!utcs!mnetor!seismo!lll-crg!nike!ucbcad!pavepaws!chapman
From: chapman@pavepaws.UUCP
Newsgroups: net.micro.pc
Subject: Re: Simple Environment Question
Message-ID: <854@ucbcad.BERKELEY.EDU>
Date: Mon, 14-Jul-86 21:52:10 EDT
Article-I.D.: ucbcad.854
Posted: Mon Jul 14 21:52:10 1986
Date-Received: Tue, 15-Jul-86 04:52:33 EDT
References: <10800008@mcomp>
Sender: news@ucbcad.BERKELEY.EDU
Reply-To: chapman@pavepaws.UUCP (Brent Chapman)
Organization: UNIXversity of California at Berkeley
Lines: 28

The following information is for DOS 3.x; I am unsure of its applicability
to earlier versions.

The segment address of a program's copy of the environment is stored at
offset 0x2C in the PSP.  It is stored as a series of ASCII strings
(totallyng less than 32K) in the form "NAME=parameter".  Each string is
terminated by a byte of zeros.  A second byte of zeros follows the last
string in the environment.

The address of the PSP can be obtained by using interrupt 0x21, function
0x62.  Set AH to 0x62, cause an interrupt 0x21, and read the PSP
address from register BX.

Note that what your program sees is a COPY of the environment of the
calling process (generally COMMAND.COM).  Therefore, any changes you
make to this environment will be visible to sub-programs that your
program calls, but will "disappear" when your program terminates.


Brent

--

Brent Chapman
chapman@pavepaws.berkeley.edu
ucbvax!pavepaws!chapman

TANSTAAFL!  (There Ain't No Such Thing As A Free Lunch!)