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Lesson 1. Basic Description Of A Computer System.

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This section has the purpose of giving a brief outline of the main components a of computer system at a basic level, which will
allow the user a greater understanding of the concepts which will be dealt with throughout the tutorial.
Central Processor
Central Memory
Input and Output Units
Auxiliary Memory Units

Computer System.

The term computer system refers to the complete configuration of a computer, including the peripheral units and the system
programming which make it a useful and functional machine for a determined task.

Central Processor.

This part is also known as central processing unit or CPU, which in turn is made up by the control unit and the arithmetic and
logic unit.
Its functions consist in reading and writing the contents of the memory cells, to forward data between memory cells and special
registers, and decodify and execute the instructions of a program. The processor has a series of memory cells which are used
very often and thus, are part of the CPU.

Information Systems General Coordination.
These cells are known with the name of registers. A processor may have one or two dozens of these registers. The arithmetic
and logic unit of the CPU realizes the operations related with numeric and symbolic calculations. Typically these units only
have the capacity of performing very elemental operations such as: the addition and subtraction of two whole numbers, whole
number multiplication and division, handling of the registers' bits and the comparison of the contents of two registers.
Personal computers can be classified by what is known as word size, this is, the quantity of bits which the processor can handle
at a time.

Central Memory.

It is a group of cells, now being fabricated with semi-conductors, used for
general processes, such as the execution of programs and the storage of
information for the operations.

Each one of these cells may contain a numeric value and they have the property of being directional, that is they can
distinguish one from another by means of a unique number or an address for each cell.

The generic name of these memories is Random Access Memory or RAM.

The main disadvantage of this type of memory is that the integrated circuits lose the information they have stored when the
electricity flow is interrupted. This was the reason for the creation of memories whose information is not lost when the system
is turned off. These memories receive the name of Read Only Memory or ROM.
Input and Output Units.

In order for a computer to be useful to us it is necessary that the processor
communicates with the exterior through interfaces which allow the input and
output of information from the processor and the memory. Through the use of
these communications it is possible to introduce information to be processed and
to later visualize the processed data.

Some of the more common input units are keyboards and mice. The more common output units are screens and printers.

Auxiliary Memory Units.

The central memory of a computer is very costly. Considering today's
memory hungry applications, the need to create practical and
economical information storage systems arises.

Besides, the central memory loses its content when the machine is turned off, therefore making it inconvenient for the permanent
storage of data.

These and other inconveniences give place for the creation of peripheral units of memory which receive the name of auxiliary
or secondary memory. Of these the most common are magnetic discs and tapes.

The stored information on these magnetic means receive the name of files. A file is made up of a variable number of registers,
generally of a fixed size; the
registers may contain information or programs.

Advantages of the Assembler
The first reason to work with assembler is that it provides the opportunity of
knowing more about the operation of your PC, which allows the development of software in a more consistent manner.

The second reason is it provides for the total control of the PC.

Third, assembly programs are quicker, smaller, and have larger
capacities than ones created with other languages.

Lastly, the assembler allows an ideal optimization in programs, be it on their size
or on their execution.

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