Browse Prior Art Database

Priority Controlled Advance Program Level

IP.com Disclosure Number: IPCOM000075203D
Original Publication Date: 1971-Aug-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 69K

Publishing Venue

IBM

Related People

Evans, WO: AUTHOR [+3]

Abstract

A method is provided to cause an Interrupt Routine to return control to a specific program in a computer system. This is done indirectly by causing all other programs to execute Release Control (REL).

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Priority Controlled Advance Program Level

A method is provided to cause an Interrupt Routine to return control to a specific program in a computer system. This is done indirectly by causing all other programs to execute Release Control (REL).

The central processing unit (CPU) of the computer system has the capability of containing more than one program, each having its own Instruction Address Register (IAR). A program has exclusive use of all CPU facilities while it is executing and it retains this exclusive use until it executes an instruction giving control to another program.

The CPU also has an Interrupt Routine which is given immediate control upon request from some source in the computer system, but external to the CPU. The method is divided into two distinct sections. The first, Fig. 1, identified as SAVE, is incorporated in the Interrupt Routine and the second, called RES, is in the program level to which control will be given.

The assumed priority program is program 1, Fig. 2, but any program can be assigned priority.

SAVE stores programs 1 through n IAR's for RES. Program 1 IAR is changed to RES. When program 1 gains control, RES is executed. Programs 2 through n are changed to REL causing program 1 to gain control.

RES restores the IAR for programs 2 through n so these levels continue execution at the same instruction before the interrupt. SWITCH and PROTECT are used because RES can be interrupted. SWITCH prevents saving IAR's and changing program 1 IA...