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From: rde@ukc.UUCP
Newsgroups: net.micro.pc
Subject: Re: Simple Environment Question
Message-ID: <1716@eagle.ukc.ac.uk>
Date: Fri, 18-Jul-86 06:12:10 EDT
Article-I.D.: eagle.1716
Posted: Fri Jul 18 06:12:10 1986
Date-Received: Mon, 21-Jul-86 05:58:03 EDT
References: <10800008@mcomp> <854@ucbcad.BERKELEY.EDU>
Reply-To: rde@ukc.ac.uk (R.D.Eager)
Organization: U of Kent at Canterbury, Canterbury, UK
Lines: 30

In article <854@ucbcad.BERKELEY.EDU> chapman@pavepaws.UUCP (Brent Chapman) writes:
>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.
>

All versions of DOS from 2.00 onwards have a way of getting to the PSP.
It isn't however the INT 21H call with AH=62H, which appeared later.

This generic method (and it *is* documented) is that DS and ES both point
to the PSP when the program is entered from DOS....

Hope this helps,
-- 
           Bob Eager

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