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Method for Serializing DOS System Requests Disclosure Number: IPCOM000039128D
Original Publication Date: 1987-Apr-01
Included in the Prior Art Database: 2005-Feb-01

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Related People

Bartek, BA Lovell, CJ Pierschalla, BR [+details]


A method is described for serializing personal computer (PC) disk operating system (DOS) requests. DOS has system service routines which are not reentrant. This means that if two applications try and invoke the system service at the same time, unpredictable results will occur. Normally, this would not be a problem when one application is active, but when an application which does its own multitasking is run on DOS, it is possible to have two applications each invoke a service routine. An example would be two programs trying to communicate over the asynchronous communications card. The solution is to use the "In-DOS" Flag interface to determine whether DOS is being used through an interface other than the standard DOS function call - Interrupt 21. The "In-DOS" Flag interface is an unpublished DOS interface.