The Computer and the Brain: Abused City (The Silliman Memorial Lectures Series) by John von Neumann

Author:John von Neumann [von Neumann, John]
Language: eng
Format: epub
Publisher: Yale University Press
Published: 2017-12-13T05:00:00+00:00

Mixed Forms of Control

The two modes of control described in the above—the plugged and the memory-stored—allow various combinations, about which a few words may be said.

Consider a plugged control machine. Assume that it possesses a memory of the type discussed in connection with the memory-stored control machines. It is possible to describe the complete state of its plugging by a sequence of digits (of suitable length). This sequence can be stored in the memory; it is likely to occupy the space of several numbers, i.e. several, say consecutive, memory registers—in other words it will be found in a number of consecutive addresses, of which the first one may be termed its address, for short. The memory may be loaded with several such sequences, representing several different plugging schemes.

In addition to this, the machine may also have a complete control of the memory-stored type. Aside from the orders that go naturally with that system (cf. above), it should also have orders of the following types. First: an order that causes the plugged set-up to be reset according to the digital sequence stored at a specified memory address (cf. above). Second: a system of orders which change specified single items of plugging. (Note that both of these provisions necessitate that the plugging be actually effected by electrically controllable devices, i.e. by electromechanical relays [cf. the earlier discussion] or by vacuum tubes or by ferromagnetic cores, or the like.) Third: an order which turns the control of the machine from the memory-stored regime to the plugged regime.

It is, of course, also necessary that the plugging scheme be able to designate the memory-stored control (presumably at a specified address) as the successor (or, in case of branching, as one successor) of a control sequence point.

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