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From: ron%brl-bmd@sri-unix.UUCP
Newsgroups: net.unix-wizards
Subject: Re:  exec()
Message-ID: <3728@sri-arpa.UUCP>
Date: Tue, 2-Aug-83 14:15:33 EDT
Article-I.D.: sri-arpa.3728
Posted: Tue Aug  2 14:15:33 1983
Date-Received: Fri, 5-Aug-83 11:51:09 EDT
Lines: 10

From:      Ron Natalie 

Depending on your version of UNIX, down near the end of exec will
code to set it after it zeros all the registers it will set u.u_ar0[R7]
to zero, so that when the system returns to user mode it will start
at zero.  In newer versions, the loop that clears the registers is
replaced with a call to setregs.  In the middle of set regs it sets
u.u_ar0[PC] to the starting address specified in the a.out header.

-Ron