Match each word in column A with its definition in columnB.

A	B
1. CPU	a) performs the processing operations;
2. CU	b) carries out logical comparisons of storage;
3. ALU	c) executes basic arithmetic functions;
4. accumulator	d) coordinates the operation of the whole system;
5. clock	e) selects data from memory;
6. counter	f) produces electronic marks at regular intervals;
7. register	g) controls the flow between the primary storage and the arithmetic–logical unit;
8. decoder	h) keeps the instruction while it is being performed;
9. comparer	i) holds the results of processing operations;
10. adder	j) breaks the instructions into separate commands.

MICROPROCESSOR – A BRAIN TO THE HARDWARE

1. The microprocessor forms the heart of a microcomputer. The first microprocessors were developed in 1971 as a branch of a pocket calculator development. Since then there has been a tremendous raise of work in this field and there appeared dozens of different microprocessors. Microprocessors are used primarily to replace or increase random logic design.

As it is known computer actually refers to a computing system including hardware (processor, I/O circuits, power supplies, control panel, etc.) and software (instruction manual, user’s manual, assembler and diagnostic and service routines). Processor refers to the processing circuits: control processing unit, memory, interrupt unit, clock and timing. Most processors also include computer software.

Central processing unit – heart of the processor – consists of the register array, arithmetic and logical unit, control unit (including microROM), and bus control circuits. Microsoftware may also include microinstruction manual, microassembler, etc.

2. The very first microprocessors were fabricated using PMOS technology. “Holes” in the p-type material having a low mobility, those microprocessors were relatively slow devices. Later, improved technology permitted microprocessors to be constructed using n-type MOS and these microprocessors are almost as fast as normal minicomputers.

Some microprocessors are now made using CMOS. The speed and logic density of CMOS are inferior to n-type MOS but the process does have some significant advantages. First of all, it has low power consumption, power being consumed only when a logic element changes a state. Secondly, it can operate over a wide voltage range. As a result, electronics based on CMOS can operate successfully with “noisy” power supplies. The low consumption makes it quite possible to use a simple battery to maintain the security of supply for several weeks. This type of microprocessor has clear advantages over the other types.

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