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The Central Computer System (fig. 3-5) is made up primarily of a general-purpose, high-speed, singleaddress, binary digital, stored-program computer with associated input-output (IO) devices. The Central Computer is designed to accept large amounts of military tactical data and to process the data quickly. Generally speaking, the purpose of the Central Computer is to correlate and process data and to transfer the results to other systems of the Central.

The Central Computer is capable of adding, subtracting, multiplying, and dividing. More complicated operations such as extracting square roots and evaluating complex variables can be performed by combining the basic arithmetic operations. The computer is designed to respond to simple stereotype instructions, each of which causes the computer to perform a single arithmetic operation. An extended sequence of such instructions, resulting in the solution to a problem, is called a program.

When solving any given problem, the Central Computer actually uses only the addition process, reducing all other processes to types of addition. This is more easily accomplished in a computer by utilizing the binary rather than the decimal number system. The binary system is based on a 1 or 0 (yes or no) principle and, consequently, requires circuits with two stable conditions to indicate a 1 or a 0. The decimal system, involving 10 digits (0 to 9) would require circuits with 10 stable conditions.

The function of the Central Computer System is to process algebraically and logically the military tactical data supplied to it by the Input System via the Drum System, transferring the results back to the Drum System for subsequent distribution to the Display and Output Systems.

In addition to processing data, the Central Computer System operates as the main control for the Central. As data is being processed, the Central Computer generates signals, as instructed, and sends them to the Drum System for utilization by the Input, Display, and Output Systems. These signals control the flow of data between systems, initiate operational cycles, set up control circuits for the coming operations and, in general. synchronize the actions of each system with those of the Central Computer System.

Functionally, the Central Computer System is divided into seven groups:
a. Instruction control element
b. Selection control element
c. Program control element
d. Arithmetic element
e. Internal storage devices
f. Associated IO units
g. Manual controls and computer indicators

The instruction, selection, and program control elements sequence, co-ordinate, and control all processes in or allied with the operation of the computer. The entire instruction control element and a part of the program control element govern internal computer operations, while the selection control element and the remaining part of the program control element govern external computer operations primarily connected with 10 devices.

Chapter 3, Page 18

The arithmetic element performs arithmetic processes using numerical data as instructed by the program. The associated 10 units are commercial IBM machines modified for use with the computer and are not to be confused with the Input and Output Systems of the Central. The manual control facilities enable personnel to start, operate, shut down, and service the computer.