Browse Prior Art Database

Character Display System

IP.com Disclosure Number: IPCOM000078315D
Original Publication Date: 1972-Dec-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 4 page(s) / 61K

Publishing Venue

IBM

Related People

Will, PM: AUTHOR

Abstract

This display system makes it feasible to store textual information containing a large number of composite characters in records of fixed size, which are no greater in length than records normally required to store lines that are free of such characters.

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Character Display System

This display system makes it feasible to store textual information containing a large number of composite characters in records of fixed size, which are no greater in length than records normally required to store lines that are free of such characters.

A composite character, or "composite," is a symbol which is formed from several input characters, but occupies only a single-character space in the display. An example would be a subscript (which is represented in the input stream as a "down" symbol followed by an alphanumeric character), a superscript ("up" followed by an alphanumeric character), or a combination subscript-superscript, which is formed from five symbols (down-character- backspace-up-character). The presence of large numbers of such characters in the input information ordinarily complicates the problem of storing the information which is to be displayed, particularly where it is desired that the line and page boundaries in storage be consistent with the line and page boundaries in the display.

The proposed system enables each composite to be stored in the same amount of record space that is needed to store an ordinary character. For instance, if a normal character is represented in storage by a video code consisting of eight bits (one byte), a composite character likewise is represented by an 8-bit video code. There are 256 possible combinations of eight bits, and not more than half of these are needed to represent characters in normal use, leaving at least 128 codes available to represent special characters such as composites. Thus, the composites will require no more storage space than other characters, if they are represented by these normally unused video codes.

A convenient way of distinguishing between the standard ID's (code numbers assigned to standard characters) and composite ID's (code numbers assigned to composite characters), is to assign codes having 0 in the eighth-bit position to standard ID's and codes having 1 in the eighth-bit position to composite ID's. This enables composite ID's to be detected by means of very simple circuitry. If the established coding scheme does not permit this, somewhat more elaborate detection circuitry will be needed to distinguish between the two types of ID's, but the system will still offer significant advantages. The assignment of code numbers to composite ID's need not remain fixed from page-to-page.

A character generating system having the capability of handling composites in the above fashion will include, in addition to the conventional circuitry, the following elements: a) A random-access memory (RAM) which stores the video data for composite characters, as distinguished from the read-only memory (ROM) which stores the video data for standard single characters. b) An offset register in which there may be stored a plus or minus indication, to denote whether the character is to be shifted upwardly (superscript) or downwardly (subscript) in...