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The DOS COMMAND Processor As a Monitor in a Multitasking Personal Computer

IP.com Disclosure Number: IPCOM000060300D
Original Publication Date: 1986-Mar-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Ebrahimi, M: AUTHOR [+4]

Abstract

Consider a multitasking operating system for the IBM Personal Computer (PC) which extends the Disk Operating System (DOS) with various facilities for multiprocessing, but utilizes DOS functions to the extent possible to avoid any duplication. The system is implemented as a program that is loaded by DOS like any other program but remains in charge thereafter (that is, the loaded program never terminates). In DOS, command processing is the responsibility of a component called COMMAND.COM, which is loaded when DOS is initialized. Its function is to prompt the user for a command, load the corresponding program, and initiate its execution. Until the program terminates, COMMAND.COM remains in a waiting state and no other command can be processed.

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The DOS COMMAND Processor As a Monitor in a Multitasking Personal Computer

Consider a multitasking operating system for the IBM Personal Computer (PC) which extends the Disk Operating System (DOS) with various facilities for multiprocessing, but utilizes DOS functions to the extent possible to avoid any duplication. The system is implemented as a program that is loaded by DOS like any other program but remains in charge thereafter (that is, the loaded program never terminates). In DOS, command processing is the responsibility of a component called COMMAND.COM, which is loaded when DOS is initialized. Its function is to prompt the user for a command, load the corresponding program, and initiate its execution. Until the program terminates, COMMAND.COM remains in a waiting state and no other command can be processed. It would appear that no DOS commands could be processed until the multitasking system terminates. However, the multitasking system assumes the role of an operating system, and, as such, never terminates. On the other hand, it should also support DOS commands, and preferably do so using COMMAND.COM. There is a scheduling conflict between COMMAND.COM and the multitasking program. The solution makes use of the fact that in DOS, an application process may execute a DOS command by invoking a second copy of the command processor. The application process passes the command as a parameter to the second command processor. The second command processor executes th...