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From: ralf@b.gp.cs.cmu.edu (Ralf Brown)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Dos Func. 4B emulation
Message-ID: <7676@pt.cs.cmu.edu>
Date: 23 Jan 90 05:15:17 GMT
References: <844@ocsmd.ocs.com> <8283@cg-atla.UUCP> <8ZiwoM600WB8QxSWwE@andrew.cmu.edu>
Organization: Carnegie-Mellon University, CS/RI
Lines: 27

In article <8ZiwoM600WB8QxSWwE@andrew.cmu.edu> bk0y+@andrew.cmu.edu (Brian Christopher Kircher) writes:
}In article <8283@cg-atla.UUCP> fredex@cg-atla.UUCP (Fred Smith) writes:
}>I don't understand--Int 21 function 0x4B is a function of DOS, not
}>the shell ( command.com) `As long as you have DOS you don't need
}>to "emulate" function 4B.
}
}But Int 21 function 0x4B is part of command.com.  Quoting IBM's DOS
}Technical Reference Manual under its description of the various parts
}of command.com:
}	"A transient portion is loaded at the high end of memory.
}	 This is the command processor itself, containing ... a
}	 routine to load and execute external commands.  This 'loader'
}	 is at the highest end of memory, and is invoked by the EXEC
}	 function call to load programs."

This, however, is true ONLY of PC-DOS 2.x.  MS-DOS 2.x and up, as well as
PC-DOS 3.0 and up, contain the INT 21/AH=4Bh code in IBMDOS.COM/MSDOS.SYS.
(the description is in fact not quite correct, since the PCDOS 2.x EXEC
code is contained in a *second* transient portion of COMMAND.COM which is
not loaded until EXEC is called)


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