Chapter 4 Preliminary discussion of the logical design of an electronic computing instrument 117
timing circuits in sequence. When a given timing circuit has completed its operation, it emits a pulse which should go to the timing circuit to be used next. Since this depends upon the particular operation being executed, these pulses are routed according to the signals received from the decoding and recoding function tables activated by the six binary digits specifying an order.
6.8. In this section we will consider what must be added to the control so that it can direct the mechanisms for getting data into and out of the computer and also describe the mechanisms themselves. Three different kinds of input-output mechanisms are planned.
First: Several magnetic wire storage units operated by servo-mechanisms controlled by the computer.
Second: Some viewing tubes for graphical portrayal of results.
Third: A typewriter for feeding data directly into the computer, not to be confused with the equipment used for preparing and printing from magnetic wires. As presently planned the latter will consist of modified Teletypewriter equipment, cf. 6.8.2 and 6.8.4.
6.8.1. Since there already exists a way of transferring numbers between the Selectrons and Ac, therefore Ac may be used for transferring numbers from and to a wire. The latter transfer will be done serially and will make use of the shifting facilities of Ac. Using Ac for this purpose eliminates the possibility of computing and reading from or writing on the wires simultaneously. However, simultaneous operation of the computer and the input-output