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Conditional Arithmetic and Logical Instructions

IP.com Disclosure Number: IPCOM000073832D
Original Publication Date: 1971-Feb-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Matlack, RC: AUTHOR

Abstract

In the execution of many programs, it is often necessary to control branching in accordance with the value of a data word. Previously, this has required the loading of a data word into an accumulator, the processing of the word with one of the test words and the loading of the result back into the accumulator and simultaneously testing for a zero result. Since the word in the accumulator is replaced by each processed result, a reloading is needed for each test.

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Conditional Arithmetic and Logical Instructions

In the execution of many programs, it is often necessary to control branching in accordance with the value of a data word. Previously, this has required the loading of a data word into an accumulator, the processing of the word with one of the test words and the loading of the result back into the accumulator and simultaneously testing for a zero result. Since the word in the accumulator is replaced by each processed result, a reloading is needed for each test.

The new conditional instructions CXOR, CAND, COR and CADD may be used to perform all of these functions except that the result is not returned to the accumulator. Since we would be looking for an all zero or all ones result, we do not care what other result is generated and it can be lost without damage. Such processing leaves the data word in the accumulator for use in the next test and saves reloading.

The conditional Exclusive OR (CXOR) can, for example, be used in testing to see if a data word is equal to one of a list of test words, the conditional AND (CAND) can test data words for the absence of bits in selected orders only, the conditional OR (COR) can similarly test for the presence of bits in selected orders and the conditional ADD (CADD) can be used to generate a carryout signal if the data word is equal to or greater than the magnitude of each of a group of test words.

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