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Retention of Operands in Push Down Stacks

IP.com Disclosure Number: IPCOM000090217D
Original Publication Date: 1969-Mar-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Driscoll, GC: AUTHOR [+2]

Abstract

The system provides memory hardware and controls so that operands can be selectively retained in a push-down store PDS. Normally, operands are lost as they are read out. A special retention field is added to each instruction in Instruction Register 10, which field specifies which data is to be retained and in what order the data is to appear in the stack. In the written form of the instruction, omission of the retention field for all operands indicates that only the result is to be retained. Any of various notations can be used to specify retention. For instance, ADD (2,1,R) indicates that what is next to the top of the stack is to be placed at the top, what was at the top is to be placed second, and the result of adding these two quantities is to be placed third.

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Retention of Operands in Push Down Stacks

The system provides memory hardware and controls so that operands can be selectively retained in a push-down store PDS. Normally, operands are lost as they are read out. A special retention field is added to each instruction in Instruction Register 10, which field specifies which data is to be retained and in what order the data is to appear in the stack. In the written form of the instruction, omission of the retention field for all operands indicates that only the result is to be retained. Any of various notations can be used to specify retention. For instance, ADD (2,1,R) indicates that what is next to the top of the stack is to be placed at the top, what was at the top is to be placed second, and the result of adding these two quantities is to be placed third. Likewise, ADD (R,2) indicates the disappearance of what is at the top, the placing at the top of the sum of these two quantities, and the leaving in place of what is second. Decoder 12 provides the necessary instructions to PDS controls 14 which include necessary registers for holding operands and results and the controls for replacing them in PDS 16 in the specified order as indicated by the retention field.

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