Von Neumann: The Computer: Logical Control (The Computer and the Brain)

computerbrain2Logical Control is essentially how one determines the fixed order to perform logical functions to produce the desired result. This is programming the machine.

So you have the numerical data that is input, you have the organs that perform basic mathematical functions, you have instructions as to the order in which those functions are performed, and you then have the output data.

Beyond being able to perform basic functions, the machine must also have the capacity to perform a sequence/logical pattern to solve mathematical problems, which is actually the goal in the first place. So in analog machines there must be enough components that can perform basic functions as needed for the calculation. They must be connected to each other in a fixed setting for the duration of solving the problem.

It is possible to have only one component for each basic function, but this then requires that there be another organ in the machine to remember numbers—it must be able to remember a number, replace the number in its memory, and also repeat upon being questioned for it. This is called ‘memory’ and the totality of memory organs is a ‘memory register’ and is the main ‘mode of control’ for digital machines.

There are a number of possibilities for controlling this sequence through what is an iterative approach—I’m assuming through a series of IF/THEN sorts of controls.

In “memory stored control”, rather than having physical controls, the controls are stored in the machine’s memory—essentially, the “program” is no longer a physical thing (i.e., a punchcard), but can be stored in the same way that numbers can be stored—within the machine itself.

What makes this remarkable further is the numbers and programs can begin manipulating themselves from within the machine.

These types of controls can be combined, so that a memory stored control could consist of orders that reset plugged (physical) controls, change plugged control setups, and control of the machine over to the plugged “regime”. By the same token, the plugged “scheme” should be able to hand back over control of the machine to the memory stored control scheme at some point in its sequence.

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