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Read the text and find out if you answered the questions (in exercise 1) correctly.

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  10. Exercise 1. Vocabulary to the text.

The nerve center of a microcomputer is the central processing unit or CPU. This unit is built into a single microprocessor chip – an integrated circuit –, which executes program instructions and supervises the computer’s overall operation. The unit consists of three main parts:

a) the control unit, which examines the instructions in the user’s program, interprets each instruction and causes the circuits and the rest of the components – disk drives, monitor, etc. – to be activated to execute the functions specified;

b) the arithmetic logic unit (ALU), which performs mathematical calculations (+, -, etc.) and logical operations (and, or, etc.);

c) the registers, which are high-speed units of memory used to store and control information. One of these registers is the program counter (PC), which keeps track of the next instruction to be performed in the main memory. Another is the instruction register (IR), which holds the instruction that is currently being executed.

One area where microcomputers differ is in the amount of data – the number of bits – they can work with at a time. There are 8, 16, 32 and 64-bit processors, and the computer’s internal architecture is evolving very quickly.

The programs and data, which pass through the central processor, must be loaded into the main memory (also called the internal memory) in order to be processed. Thus, when the user runs an application, the microprocessor looks for it on secondary storage devices (disks) and transfers a copy of the application into the RAM area. RAM (random access memory) is temporary, i.e. its information is lost when the computer is turned off. RAM is the basic location where the microprocessor stores the required information. The size of RAM is very important, and adding extra chips can sometimes expand the RAM capacity. These are usually contained in single in-line memory modules or SIMMs, which are installed in the motherboard of the computer. We can designate a certain amount of RAM space as a cache in order to store information that application uses repeatedly. A RAM cache can speed up our work, but it means that we need enough internal memory or a special cache card. The ROM section (read only memory) is permanent and contains instructions and routines for the basic operations of the CPU. These instructions are used to start up the computer, to read the information from the keyboard, to send characters to the screen, etc. they cannot be changed and are not erased when the power is turned off. For this reason, the ROM section is also referred to as firmware. The processor can read and use stored in the ROM chip, but cannot put information into it.

Most of today’s computers have internal expansion slots that allow users to install adapters or expansion boards. Popular adapters include high-resolution graphics boards, memory expansion boards, and internal modems.

The power and performance of a computer is partly determined by the speed of its microprocessor. A clock provides pulses at fixed intervals to measure and synchronize circuits and units. The clock speed is measured in MHz (megahertz) and refers to the frequency at which pulses are emitted. For example, a CPU running at 500 MHz (500 million cycles per second) is likely to provide a very fast processing rate and will enable the computer to handle the most demanding applications.




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