Path: utzoo!utgpu!water!watmath!clyde!ima!bbn!diamond.bbn.com!mlandau
From: mlandau@bbn.com (Matt Landau)
Newsgroups: comp.lang.c
Subject: Re: system
Keywords: fork and wait not for MSDOS
Message-ID: <10491@jade.BBN.COM>
Date: 25 Jan 88 05:04:30 GMT
References: <127@dcrbg1.UUCP> <452@picuxa.UUCP> <3920@sigi.Colorado.EDU> <1317@laidbak.UUCP> <10202@ut-sally.UUCP>
Reply-To: mlandau@bbn.com (Matt Landau)
Organization: BBN Laboratories Incorporated, Cambridge, MA
Lines: 22

In comp.lang.c (<10202@ut-sally.UUCP>), nather@ut-sally.UUCP (Ed Nather) writes:
>MS-DOS can do the same thing (create a new process and wait for it to
>finish) -- it's called "spawn()".  Look for it in your favorite manual.

The fundamental difference between Unix fork() and creation of child
processes in MS-DOS is twofold:

  (1)  When a child is created by fork(), both child and parent continue
       to run, unless the parent explicitly calls wait() to wait for the
       child to terminate.  MS-DOS is single-tasking, so creation of a 
       child process normally involves suspending the parent (but there
       are ways you can get around this and fake multitasking).

  (2)  More importantly, fork() creates a child process by *copying the 
       parent's address space* -- the child is an exact copy of the parent 
       until they take divergent execution paths.  The child process is 
       typically overlaid almost immediately by a call to exec(), but this 
       is by no means required.  MS-DOS has no way to copy a process's
       address space.
--
 Matt Landau			Waiting for a flash of enlightenment
 mlandau@bbn.com			  in all this blood and thunder