Browse Prior Art Database

Data Compression Algorithms

IP.com Disclosure Number: IPCOM000073751D
Original Publication Date: 1971-Jan-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Craft, DJ: AUTHOR

Abstract

The most frequently occurring hex digits of a data stream are extracted and a picture of the stream formed by using only one or two bits (de pending upon the number of digits extracted) to indicate the position of extracted digits in the stream. for instance, if only one digit is extracted then the picture is made up of 1's indicating the position of the extracted digit and 0's indicating the position of the remaining digits. The stream after compression comprises an algorithm identity half-byte, extracted digit identify half-byte, length of stream byte, a stream picture section and the original stream minus the extracted digits.

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Data Compression Algorithms

The most frequently occurring hex digits of a data stream are extracted and a picture of the stream formed by using only one or two bits (de pending upon the number of digits extracted) to indicate the position of extracted digits in the stream. for instance, if only one digit is extracted then the picture is made up of 1's indicating the position of the extracted digit and 0's indicating the position of the remaining digits. The stream after compression comprises an algorithm identity half-byte, extracted digit identify half-byte, length of stream byte, a stream picture section and the original stream minus the extracted digits.

A data stream, for example 80 bytes from a punched card input, is scanned for the most frequently occurring hex digit. In the example shown, X'5' is assumed to occur most often. A lead section to the stream is compiled comprising the compression algorithm identity, a half-byte containing digit '5' a half-word containing the number of bytes in the stream, in this case X'50', a bit picture of the stream which for 80 byte stream will be 10 bytes long and then the remaining digits of the stream with the digit X'5' extracted.

Algorithms may be used for extracting either the most frequently occurring digit or the two or three most common digits from a stream, in this case the picture section will require two bits per byte to identify all the extracted digits. A similar algorithm may be used for identifying the repet...