Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!zaphod.mps.ohio-state.edu!rpi!crdgw1!sixhub!davidsen
From: davidsen@sixhub.UUCP (Wm E. Davidsen Jr)
Newsgroups: comp.compression
Subject: Re: Self Extracting Files
Message-ID: <4096@sixhub.UUCP>
Date: 16 Jun 91 23:45:01 GMT
References: <309pollarda@physc1.byu.edu>
Reply-To: davidsen@sixhub.UUCP (bill davidsen)
Organization: *IX Public Access UNIX, Schenectady NY
Lines: 28

In article <309pollarda@physc1.byu.edu> pollarda@physc1.byu.edu writes:
| 
| PKZip as well as several other file compression utilities I have seen
| have the option to have the files self extracting.  I understand that
| the files have the machine code to self extract along with the data
| combined somehow.  But how exactly does it work?

  The expandor is the first part of the program, which is fixed length
so it knows what to skip.

| What tells the computer to stop loading in the file as machine code
| and handle the rest as data?

  It all gets loaded into memory in some cases, in others the header
info causes only part of the file to be loaded, and the full filename
(dos 3.x and later) is used to find the real data.


| Some programs have something embeded in them so that if you "type"
| them, they will display the program name and the material will stop
| scrolling on the screen and the DOS prompt will appear again.

  The DOS type command stops when it see a cntl-Z 26(10) character.
-- 
bill davidsen - davidsen@sixhub.uucp (uunet!crdgw1!sixhub!davidsen)
    sysop *IX BBS and Public Access UNIX
    moderator of comp.binaries.ibm.pc and 80386 mailing list
"Stupidity, like virtue, is its own reward" -me