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Data Compaction and Expansion Routine

IP.com Disclosure Number: IPCOM000074362D
Original Publication Date: 1971-Apr-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Fitzpatrick, JA: AUTHOR

Abstract

Data character sets employed for scientific applications are required to be very large. Data character sets employed in the commercial environment are much more limited. Computer systems compatible with both commercial and scientific applications must, therefore, employ the larger scientific character set. An example is the 8-bit EBCIDIC code now widely utilized.

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Data Compaction and Expansion Routine

Data character sets employed for scientific applications are required to be very large. Data character sets employed in the commercial environment are much more limited. Computer systems compatible with both commercial and scientific applications must, therefore, employ the larger scientific character set. An example is the 8-bit EBCIDIC code now widely utilized.

Converting the 8-bit code to a corresponding 6-bit code having application solely in the commercial field for the purpose of storing the data significantly affects the required storage capacity of the system.

A routine for compacting the 8-bit data is to eliminate the two bits distinguishing between normal commercial characters and the additional scientific characters. Upon expanding, or unpacking, the resultant 6-bit data, the bits designating commercial characters are reconstituted into the data. Specifically, the 2 leftmost bits of each character in the 8-bit EBCIDIC code are dropped and the new 6-bit characters shifted together. To expand (unpack) from 6-bit to 8-bit, binary "11" would be added to the left of each 6-bit representation if one of the following conditions existed: if the 1st 2 bits are and the last 4 bits are

00 0001 thru 1001

01 0001 thru 1001

10 0010 thru 1001

11 0001 thru 1001. Otherwise, binary "01" would be added.

("11" is for normal characters - 0-9 and A-Z. "01" is for special characters.)

The above-described method will handle compaction and...