2.1. PERSONAL COMPUTERS HARDWARE
2.1.1. How a computer works
Definition
An electronic computing machine (ECM), or a computer, is a set of technical and software tools designed to automate receiving, storing, processing and transmitting information.
In terms of the terminology used in computer science, most of the names are of English origin, given the advanced positions that the English-speaking countries have in this area. So the word «Computer» is much more frequently used in Russian professional literature than the abbreviation ECM, what is why those two words are used as synonyms hereinafter.
In 1945, the fundamentals of computer operation were formulated by John von Neumann in the form of three general principles: program control, uniform memory, and address capacity. To implement those principles, the following ECM structure was suggested (fig. 2.1). It was used in the first two generations though its main nodes are still used in today?s computers.
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Fig. 2.1. ECM Structure Diagram
The main units of an ECM are: Control Unit (CU), Arithmetic/Logic Unit (ALU), Random Access Memory (RAM), External Memory (EM), input and output devices. Modern computers have their arithmetic/logic unit combined with the control unit into the so-called processor. In fig. 2.1, the solid line shows the direction of information flows, and the dotted line shows the commands from the control unit.
The major computer units are intended to carry out the following tasks. ALU is intended to perform arithmetic and logical operations, that is where the tasks are solved. The Memory Unit stores the initial data, intermediate and final results of the task-solving as well as the task-solving program. The Memory Unit consists of the Random Access Memory, which interacts with the ALU and must have high operating speed, and of a slower External Memory, which stores the data not currently used by the computing process. This implements the principle of memory uniformity: by the ECM storing the data and the programs in its memory. The CU orchestrates the task-solving process and synchronizes operation work of all the ECM units. The input and output devices are intended for the input of the initial data and programs, as well as for the output of the task-solving process results.