International Business Machines Corporation

Jerold D Dwire

Kent R Demke

Michael Anthony Ko

Townsend H Porter, Jr

Joanne L Mumola

Donald T Crehan

A processor controlled character box display is provided with apparatus which permits the display of curvilinear graphics. The characters used to generate the graphics display are selected from a limited character set in read only storage (46), but by shifting the characters up or down by less than a full line index to provide additional character positions, it is possible to produce curvilinear graphics without the need for further character generation. Since the graphics display is a low resolution display, it is necessary to make a best dot selection in order to map the print bit map into the character box display.

Display of graphics using a non-all points addressable display

A technique for displaying a representation of a full page on less than an entire CRT screen in a word processing system. The full page representation uses character indicators to enable the word processing system user to appreciate format and spatial relationships with regard to page boundaries. Within the miniature page the interlinear spacing chosen by the operator for the hard copy output is properly represented. Integral line spacing is achieved by displaying blank lines as appropriate. Non-integral line spacing such as half-line spacing is achieved advantageously through manipulating the particular character construct utilized. A character representation matrix is usually blank at the top and blank or non-blank in the bottom half. Reversing top and bottom halves removes one half-line of interlinear spacing.

Multiple half-line spacing on a miniature page

There is described a technique for use in a word processing system for displaying a representation of the full page of text on less than an entire CRT screen where the full page representation is proportional to the hard copy output which eventually results. Dynamic mode switching is employed which enables the output on a given line of the display of both full size characters and miniature character representations. Dynamic mode switching also provides control of the placement of the miniature page representation on the CRT screen.

Full page representation through dynamic mode switching

A display refresh system wherein a RAM refresh buffer is tightly packed. Line start addresses in the buffer are determined by the line length such as eighty characters. With each of the lines in the refresh buffer being normally a binary number such as 128 characters in length the line start addresses are such that they do not coincide with the beginning of each line in the buffer. To assure packing they are interspersed each 80 positions sequentially within the buffer. A processor loads the address of each line start character into the pointer area of the refresh buffer. A line counter is used which counts the lines being displayed on the display. The RAM refresh buffer which contains the line start addresses and character data is first addressed by the line counter output to provide the line address. Since the refresh buffer is used as the line pointer register the output bus for pointer data and character data is common. Once the address of the first character in a line is read from the pointer area in the refresh buffer it is loaded into the refresh buffer address counter which then controls the sequential reading of characters in that line from the refresh buffer onto the data bus. Following the reading of each line the sequence is repeated, e.g., the line counter is incremented, its' count used to address the pointer register and the address contained in the pointer register loaded into the refresh buffer address counter.

Display refresh memory with variable line start addressing

A system and method for generating properly proportioned alphanumeric characters and symbols in two vertical heights with a single character generator and a minimum of associated circuitry. The bits of video data stored in the character generator are stored such that the vertical segments of diagonal portions of the characters and symbols include no more than two bits per vertical segment of the diagonal portion. The video data bits representative of the pels of circular portions of the symbols are stored in an arrangement to generate a horizontally elongated elliptical shape when the character or symbol is displayed in the shorter of the two heights. Whenever possible, the diagonal portions of characters include no more than two diagonally disposed pels in the single high character size. For representation of a single dot portion of one of the characters or symbols, a pair of video data bits is stored to generate a pair of horizontally disposed pels on the display when the character or symbol is displayed in the shorter of the two vertical heights. Translation logic is described to efficiently provide for two sizes of characters with a minimum of additional hardware and with no additional character generator memory beyond that required for the smallest characters or symbols.

Multiple height proportioned character generation

A frequency shift key modulator producing sine wave output signals of different frequencies for mark (1) and space (0) signal levels on an input 'send data' lead including a counter which divides the frequency of an input oscillator by different denominators for the mark and space signals and the output of which is synthesized to produce a stepped output approximating a sine wave and a final filter for smoothing the steps out of the output. In cases in which the mark and space output frequencies are approximately in the ratio of 1 to 2, a frequency divider is used for the mark output frequencies.

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Round Rock, TX, United States of America

Jerold D Dwire