Browse Prior Art Database

N Tables in One

IP.com Disclosure Number: IPCOM000073585D
Original Publication Date: 1971-Jan-01
Included in the Prior Art Database: 2005-Feb-22
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Lewitan, H: AUTHOR

Abstract

The present table look-up organization applies to computer systems where the addressable bit group unit is at least double the number of bits used as a unit in a translation table.

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This is the abbreviated version, containing approximately 54% of the total text.

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N Tables in One

The present table look-up organization applies to computer systems where the addressable bit group unit is at least double the number of bits used as a unit in a translation table.

"Word" will be used herein to designate a group of bits addressable as one unit by the computer, and the term "character" will refer to the number of bits used as a unit in a translation table. As an illustration, consider the IBM/1130 computer, which is a sixteen bit fixed word machine and the natural translation bit group unit (character) is 6-8 bits long. Economical utilization of core in the above illustration requires that two characters be stored per (addressable) word. See Table 1. More characters are packed per word for larger size words and/or smaller size characters. Table look-up and character extraction becomes increasingly more difficult as the number of characters per word increases above one. Additional logic is necessary to determine the word address in the table and the character number within the word. Different masks (or shift instructions) have to be used to extract the character, and the extracted character has to be positioned in a fixed part of a word or counter for processing. The table look-up is simplified by insuring that all characters of a given table occupy the same bit positions within a word. To maintain storage economy, other translation tables are stored side by side in the same computer table occupying the remaining word bits. This sim...