IBM 780
| Company type | Computer hardware |
|---|---|
| Industry | Computer graphics, Data processing |
| Founded | 1954 |
| Products | Vector graphics recorder |
The IBM 740 CRT Recorder, launched in 1954, was engineered to operate with the IBM 701, IBM 704, and IBM 709 computer systems, enabling the creation of vector graphics by plotting points directly onto 35 mm photographic film. This device incorporated digital-to-analog converters alongside a 7-inch, high-precision electrostatic CRT, featuring a raster dimension of 1,024 by 1,024 pixels; however, it was limited to displaying only 256 distinguishable points per line. The recorder could render points at two intensity levels and was capable of drawing vertical or horizontal lines extending from any given point to the edges of the screen, effectively generating axes.
Each point displayed corresponded to a 36-bit data word, which included 10 bits dedicated to the X coordinate, another 10 bits for the Y coordinate, and 3 control bits that managed intensity and axis line drawing. Activating both axis control bits simultaneously resulted in a diagonal line at a 45-degree angle.
The CRT in the IBM 740 utilized P11 phosphor known for its short persistence. Film was housed in magazines capable of holding up to 100 feet of ASA 200 speed 35 mm film, which could be advanced through computer commands.
Serving as a companion to the 740, the IBM 780 CRT Display featured a larger 21-inch screen with longer-lasting P7 phosphor (approximately two seconds persistence), enabling operators to observe the graphics being produced on the IBM 740’s CRT in real time.
References
- IBM 709 Data Processing System, Form A22-6501-0, 1958, p. 106ff.