Article View: comp.sys.ibm.pc.programmer
Article #1427Re: idling in the interpreter
From: Joseph H Allen
Date: Fri, 02 Mar 1990 01:48
Date: Fri, 02 Mar 1990 01:48
17 lines
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1538 bytes
In article <25EDB1B8.4B34@deimos.cis.ksu.edu> mac@harris.cis.ksu.edu (Myron A. Calhoun) writes:
:> "DOS keeps a one-byte flag, which is usually called the InDOS flag
:> or the DOS Active byte. The value of this flag at any instant
:> equals the number of calls to INT 21h functions which are currently
:> in process of execution. In particular, if the value is zero no
:> DOS function is presently active and so DOS functions can be safely
:> called. Finding the value of the InDOS Flag is easy: a call to
:> function 34h of INT 21h returns the address of the flag in es:bx."
However, the indos flag is not reliable (this is Microsoft we're dealing with
here, folks). A second byte after the indos byte also indicates times when
dos is running and these flags are not necessarily both set at the same time.
Therefore it's safest to check the word at es:bx for 0.
--
"Come on Duke, lets do those crimes" - Debbie
"Yeah... Yeah, lets go get sushi... and not pay" - Duke
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Path: arc1-ca.pugleaf.net!utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!purdue!bu.edu!m2c!wpi!jhallen From: jhallen@wpi.wpi.edu (Joseph H Allen) Newsgroups: comp.sys.ibm.pc.programmer Subject: Re: idling in the interpreter Message-ID: <9358@wpi.wpi.edu> Date: 2 Mar 90 01:48:31 GMT References: <PAS.90Mar1120125@saffron.lcs.mit.edu> <25EDB1B8.4B34@deimos.cis.ksu.edu> Reply-To: jhallen@wpi.wpi.edu (Joseph H Allen) Distribution: usa Organization: Worcester Polytechnic Institute, Worcester ,MA Lines: 17