Browse Prior Art Database

Dynamic Message Coding

IP.com Disclosure Number: IPCOM000087640D
Original Publication Date: 1977-Feb-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 3 page(s) / 44K

Publishing Venue

IBM

Related People

Wild, D: AUTHOR

Abstract

Communication channel capacity and/or transmission time can be saved by the following method for coding a sequence of alphanumeric characters representing variable-length words of natural language text, statements of a program, etc.

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Dynamic Message Coding

Communication channel capacity and/or transmission time can be saved by the following method for coding a sequence of alphanumeric characters representing variable-length words of natural language text, statements of a program, etc.

Information is coded in two alternative modes. Frequently occurring text words, which are stored in a list, are each coded as a whole word by a single assigned code word. All other words, not stored in the list, are decomposed into characters each of which is coded by a single code word. The code words used are of a common standard format for both coding modes, e.g., 8-bit bytes including one flag bit for distinguishing between modes. The list of most frequently used text words having assigned code words is maintained both at the sender and receiver, and may be updated at regular intervals to reflect changes in the frequency count over a given interval.

A device for implementing this method is shown in block form in the drawing. It is assumed that the text words are delimited by "blank" characters.

Sender. Characters appearing at input I 1 are converted to 7-bit code-words (e.g., USASCII) in coder 1, and consecutive characters are collected in buffer 2. Blank detector 3 indicates when a full word is available in buffer 2, which is then transferred to A-Register 4. Storage block 5 is provided for storing 128 most frequently used text words, i.e., variable-length coded-character strings with a maximum length of 16 characters. After a word is transferred to A-Register 4, it is compared in comparator unit 6 with all words stored in storage block 5 under the control of control unit 7. The current storage address is held in I-Register 8. This storage address is fixed-length 7-bit code word which is to be used instead of the text word contained in the respective storage location and temporarily held in B-Register 9.

When a match occurs, the contents of I-Register 8 is gated to output buffer
10. If no match occurs, the original alphanumeric word, i.e., the string of 7-bit coded characters is gated to output buffer 10. To distinguish between character- mode and word-mode code words, an eighth bit is attached as a flag...