Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!rochester!pt.cs.cmu.edu!b.gp.cs.cmu.edu!Ralf.Brown@B.GP.CS.CMU.EDU
From: Ralf.Brown@B.GP.CS.CMU.EDU
Newsgroups: comp.sys.ibm.pc
Subject: Re: Current Process in MSDOS
Message-ID: <246d8c3e@ralf>
Date: 14 May 89 14:25:02 GMT
Sender: ralf@b.gp.cs.cmu.edu
Organization: Carnegie Mellon University School of Computer Science
Lines: 30
In-Reply-To: <2949@rti.UUCP>

In article <2949@rti.UUCP>, bcw@rti.UUCP (Bruce Wright) writes:
}In article <13777@steinmetz.ge.com>, dixon@sagittarius.steinmetz (walt dixon) writes:
}> functions to retrieve this value.  The PSP manipulation services do no stack
}> switching and are always safe (if properly used) -- at least in all DOS 3.1
}> and above.  Don't know about DOS 4.0 and 4.0.1.
}
}The PSP
}functions (as well as a number of other useful functions) did not exist 
}in earlier versions of the system; they are new (or at least newly 
}supported) with 3.0.

They were introduced, but undocumented, in DOS 2.0, and a separate (but
identical) documented "get PSP" call was added with 3.0.  DOS 1.x didn't have
the PSP functions, since it had no notion of a process ID, no memory control
blocks, no DOS calls, etc. that would require knowing the current PSP.

}  Many programs want to do some of those things
}without checking the version number all the time (which is what they 
}SHOULD do, but ...).  This has had to be done because the market has 
}demanded that most applications work on almost any version of DOS -- 
}even the brain-dead V1.0.  

It's been a long time since I've seen a program that runs on DOS 1.x, and the
last one I've seen that did was quite old even then.
--
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