Although the video unit (as the IBM 2250) is the most powerful and simple input-output device, because of the high interactivity and of the simplicity of use by designers without particular knowledge of computers offered by the light pen, it has to be pointed out that the structure of the programs and the way in which the data are organized in memory permit the use of a different hardware. Having also available a hybrid computer, the authors have developed circuits and techniques to obtain the display on a simple general purpose CRT; the philosophy of the procedure consists in using a portion of the analog computer as a graphic peripheral of the digital machine. This is attractive for those users having a hybrid computer, because does not require additional expenses. Obviously this method is less powerful and immediate, but a good interactivity can be maintained; while in the case of the video unit the elements will be input pointing with the light pen their graphic symbols on the screen, with the second method they will be individuated with groups of letters, using the teletype or by a “joystick” obtained via the pots of the analog computer. Fig. 41 shows the structure of the circuits used. Considerable care has been taken in the circuit in order to minimize the amount of data to be exchanged between the analog and the digital computer and the number of analog components.
KeywordsGraphic Symbol General Purpose Analog Computer Automatic Design Digital Computer
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