Editing IBM 740

{{Short description|Early computer graphics display, 1954}}
{{Use mdy dates|date=April 2019}}
{{Infobox information appliance
| name         = IBM 740 and 780
| title        = 
| aka          = IBM 740 CRT Recorder and IBM 780 CRT display
| logo         = 
| image        = IBM_704_mainframe.gif
| caption      = An IBM 704 computer, with an IBM 780 CRT display (Image courtesy of [[Lawrence Livermore National Laboratory|LLNL)]]
| developer    = 
| manufacturer = [[IBM]]
| family       = 
| type         =  point display with generated axis
| generation   = 
| releasedate  = 1954
| lifespan     = 
| price        = {{USD|2850|1954}} a month rental 
| discontinued = 1959
| unitssold    = 
| unitsshipped = 
| media        = 35 mm photographic film
| os           = 
| power        = 
| soc          = 
| cpu          = [[IBM 701]], [[IBM 704]], [[IBM 709]]
| memory       = 
| storage      = 
| memory card  = 
| display      = 7 inch CRT with P11 [[Phosphor#Standard phosphor types|phosphor]] (740); 21 inch CRT with P7 phosphor (780)
| graphics     = 1024 x 1024 two level pixels (256 x 256 resolvable)
| sound        = 
| input        = 
| controllers  = 
| camera       = 
| touchpad     = 
| connectivity = 
| platform     = 
| service      = 
| dimensions   = 
| weight       = 
| topgame      = 
| compatibility= 
| predecessor  = 
| successor    = [[IBM 2250]]
| related      = 
| website      = <!--{{URL|example.org}}-->
}}

The '''IBM 740 CRT Recorder''' was announced in 1954 and used with the [[IBM 701]], [[IBM 704]], and [[IBM 709]] [[computer]]s to draw [[vector graphics]] images, point by point, on [[35mm format|35 mm]] [[photographic film]] (i.e. [[microfilm]]). The 740 [[film recorder]] contained [[digital-to-analog converter]]s and a 7-inch, high precision, [[electrostatic]] [[cathode-ray tube|CRT]]. The raster size was 1,024 by 1,024, but only 256 resolved spots could be displayed on a vertical or horizontal line. Points could be displayed in one of two intensities, and a line could be drawn from a point, vertically or horizontally, to the edge of the display to form an axis.

Each point to be displayed was stored in a single 36-bit word, with 10 bits each for the X and Y coordinates, and 3 control bits, one to set either high or low intensity and two to indicate that an X or Y axis is to be drawn starting from the given point. If both the X and Y axis bits were set, a 45-degree line was drawn.

The 740's CRT used a short persistence ''P11'' [[Phosphor#Standard phosphor types|phosphor]]. The film used was 35&nbsp;mm and was stored in a magazine that could hold up to 100 feet. [[American National Standards Institute|ASA]] 200 [[film speed|speed film]] was recommended. The film could be advanced under computer control.

The '''IBM 780 CRT Display''' was a monitor that could be attached to the 740 and mirror to an operator what was being drawn on 740's CRT. The 780 had a 21-inch CRT with a longer persistence (2 second, nominal) ''P7'' phosphor.

==See also==
*[[IBM 2250]]
*[[Phosphor#Standard phosphor types]]

==References==
*[[IBM]] 709 Data Processing System, Form A22-6501-0, 1958, p.&nbsp;106ff.
*{{web archive|url=https://web.archive.org/web/20110805121729/http://www-03.ibm.com/ibm/history/exhibits/701/701_1415bx40.html|title=IBM 740 Cathode ray tube output recorder}}
*{{cite book|url=https://www.cambridgescholars.com/resources/pdfs/978-1-5275-0650-3-sample.pdf|title=First Generation Mainframes-The IBM 700 Series|author=Stephen H. Kaisler|publisher=Cambridge Scholars|date=2018}}{{rp|p.15}}

==External links==
*[https://web.archive.org/web/20060209063639/https://www.reprise.com/host/tektronix/reference/phosphor1.asp]

[[Category:IBM display devices|740]]
[[Category:IBM 700/7000 series|Display 740]]
[[Category:History of human–computer interaction]]


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