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Multiple Entry Point Procedure Initialization

IP.com Disclosure Number: IPCOM000078139D
Original Publication Date: 1972-Nov-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Tobias, RL: AUTHOR

Abstract

This procedure is an efficient method for coding a multiple entry point, in which processing associated with each entry point requires the execution of a common initialization instruction sequence. This method requires instruction modification, and so can be applied only in a nonreentrant environment. Furthermore, this technique is useful only where a single exit point is needed or else storage efficiency is lost.

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Multiple Entry Point Procedure Initialization

This procedure is an efficient method for coding a multiple entry point, in which processing associated with each entry point requires the execution of a common initialization instruction sequence. This method requires instruction modification, and so can be applied only in a nonreentrant environment. Furthermore, this technique is useful only where a single exit point is needed or else storage efficiency is lost.

An example of the method is shown below in IBM System 7 Assembler Language. The instructions ENT1, ENT2, ENT3...., ENT(n) are procedure entry
points corresponding to functions FNC1, FNC2, FNC3...., FNC(n), respectively. Procedure execution beginning at a particular entry point, causes the branch instruction at label EXEC to be incremented to reference the appropriate function branch instruction. As an example, if ENT (n-1) is entered, then there will be two increments to reference the appropriate branch instruction. Initialization instructions, beginning at label INIT are executed between procedure entry and function execution. The branch instruction at label EXEC is restored, during the procedure exit sequence when serial reusability is required.

An example instruction sequence is as follows:

ENT1 AS EXEC Increment Execution Branch

ENT2 AS EXEC Increment Execution Branch

ENT(n-1) AS EXEC Increment Execution Branch

ENT(n) EQU * Entry (n) - No Increment

INIT EQU * Begin initialization sequence

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EXEC B * B...