IBM 2250
Encyclopedia
The IBM 2250 Graphics Display Unit was announced as part of System/360
in 1964. Unlike most modern computer display
s, which show images in raster format, the IBM 2250 used vector graphics
. A display list of line segments (vectors) on a 1024 by 1024 grid was stored in the computer
's memory and repainted on the 2250s CRT
up to 40 time per second. Characters were built of line segments specified by display list subroutines. Thus any character set or font
could be displayed, although fonts were generally extremely simplified for performance reasons. The computer altered the display by changing the display list. As the display list got longer, the refresh time got longer too and eventually the display would start to flicker.
The 2250 was housed in a desk with an alphanumeric (QWERTY) keyboard and a separate programmed function keyboard which had keys, indicator lights and switches. A plastic overlay label could be placed over the function keyboard. Punches on the top edge of the overlay could be sensed by the computer so the keys, lights and switches could be reprogrammed simply by changing overlays. The 2250s CRT measured 21" diagonal, but the useful display area was 12 inch by 12 inch. A light pen
was provided as a pointing device
, serving the function of the modern computer mouse.
An IBM 2285 Display Copier could be attached to the 2250 to provide 8½ by 11 inch hard copy of the display contents under operator control.
System/360
The IBM System/360 was a mainframe computer system family first announced by IBM on April 7, 1964, and sold between 1964 and 1978. It was the first family of computers designed to cover the complete range of applications, from small to large, both commercial and scientific...
in 1964. Unlike most modern computer display
Computer display
A monitor or display is an electronic visual display for computers. The monitor comprises the display device, circuitry, and an enclosure...
s, which show images in raster format, the IBM 2250 used vector graphics
Vector graphics
Vector graphics is the use of geometrical primitives such as points, lines, curves, and shapes or polygon, which are all based on mathematical expressions, to represent images in computer graphics...
. A display list of line segments (vectors) on a 1024 by 1024 grid was stored in the computer
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
's memory and repainted on the 2250s CRT
Cathode ray tube
The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...
up to 40 time per second. Characters were built of line segments specified by display list subroutines. Thus any character set or font
Typeface
In typography, a typeface is the artistic representation or interpretation of characters; it is the way the type looks. Each type is designed and there are thousands of different typefaces in existence, with new ones being developed constantly....
could be displayed, although fonts were generally extremely simplified for performance reasons. The computer altered the display by changing the display list. As the display list got longer, the refresh time got longer too and eventually the display would start to flicker.
The 2250 was housed in a desk with an alphanumeric (QWERTY) keyboard and a separate programmed function keyboard which had keys, indicator lights and switches. A plastic overlay label could be placed over the function keyboard. Punches on the top edge of the overlay could be sensed by the computer so the keys, lights and switches could be reprogrammed simply by changing overlays. The 2250s CRT measured 21" diagonal, but the useful display area was 12 inch by 12 inch. A light pen
Light pen
A light pen is a computer input device in the form of a light-sensitive wand used in conjunction with a computer's CRT TV set or monitor. It allows the user to point to displayed objects, or draw on the screen, in a similar way to a touch screen but with greater positional accuracy...
was provided as a pointing device
Pointing device
A pointing device is an input interface that allows a user to input spatial data to a computer...
, serving the function of the modern computer mouse.
An IBM 2285 Display Copier could be attached to the 2250 to provide 8½ by 11 inch hard copy of the display contents under operator control.