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Parameter Passing Instructions

IP.com Disclosure Number: IPCOM000083535D
Original Publication Date: 1975-Jun-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Callahan, RW: AUTHOR

Abstract

Call and Return microinstructions or instructions (Fig. 1) are useful in a multiprogrammed system, for selectively passing parameters between "nested" microprograms or programs. A dedicated call stack (Fig. 2) of prearranged fixed capacity N is used in conjunction with bits 13-15 of the instruction, to manage the optional passage of parameter information between programs (call levels).

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Parameter Passing Instructions

Call and Return microinstructions or instructions (Fig. 1) are useful in a multiprogrammed system, for selectively passing parameters between "nested" microprograms or programs. A dedicated call stack (Fig. 2) of prearranged fixed capacity N is used in conjunction with bits 13-15 of the instruction, to manage the optional passage of parameter information between programs (call levels).

A program at any call level is activated by execution of a Call instruction at the preceding level (e.g., Call level 2 activated by a Call at level 1), and the preceding level is reactivated by a Return instruction at the succeeding level. The call stack holds the instruction count (IC) of the calling level at Call execution time, for use after Return execution by the succeeding level. Other stack positions are used for optional passage of parameters ("Param", "Index", "Stat").

Bit 13 of the instruction is used at execution time to control transfer or nontransfer of "Param" information between successive Call levels. Bit 14 controls optional transfer of "Index" information between levels. Bit 15 controls passing of "Stat" (status) information. When a parameter is not passed by a call the associated field of the "new level" in the stack is reset to zero. At Return time any unpassed parameter is preserved at the return executing level, and the corresponding parameter at the returned level is also unmodified.

The call stack may be an array addressed by a...