A computer has the
following units:
·
Input Unit
·
Output Unit
·
Memory Unit
·
Central Processing Unit
Block Diagram |
1. Input:
This is the process of entering data and programs in to the computer system.
You should know that computer is an electronic machine like any other machine
which takes as inputs raw data and performs some processing giving out
processed data. Therefore, the input unit takes data from us to the computer in
an organized manner for processing.
2. Storage:
The process of saving data and instructions permanently is known as storage.
Data has to be fed into the system before the actual processing starts. It is
because the processing speed of Central Processing Unit (CPU) is so fast that
the data has to be provided to CPU with the same speed. Therefore the data is
first stored in the storage unit for faster access and processing. This storage
unit or the primary storage of the computer system is designed to do the above
functionality. It provides space for storing data and instructions.
The storage unit performs the
following major functions:
• All data and instructions are
stored here before and after processing.
• Intermediate results of
processing are also stored here.
3. Processing:
The task of performing operations like arithmetic and logical operations is
called processing. The Central Processing Unit (CPU) takes data and
instructions from the storage unit and makes all sorts of calculations based on
the instructions given and the type of data provided. It is then sent back to
the storage unit.
4. Output:
This is the process of producing results from the data for getting useful
information. Similarly the output produced by the computer after processing
must also be kept somewhere inside the computer before being given to you in
human readable form. Again the output is also stored inside the computer for
further processing.
5. Control:
The manner how instructions are executed and the above operations are
performed. Controlling of all operations like input, processing and output are
performed by control unit. It takes care of step by step processing of all
operations inside the computer.
FUNCTIONAL UNITS
In order to carry out the
operations mentioned in the previous section the computer allocates the task
between its various functional units. The computer system is divided into three
separate units for its operation. They are
1) arithmetic logical unit
2) control unit.
3) central processing unit.
Arithmetic Logical Unit
(ALU) Logical Unit
Logical Unit
: After you enter data through the input device it is stored in the primary
storage unit. The actual processing of the data and instruction are performed
by Arithmetic Logical Unit. The major operations performed by the ALU are
addition, subtraction, multiplication, division, logic and comparison. Data is
transferred to ALU from storage unit when required. After processing the output
is returned back to storage unit for further processing or getting stored.
Control Unit (CU)
The next component of computer
is the Control Unit, which acts like the supervisor seeing that things are done
in proper fashion. Control Unit is responsible
for coordinating various
operations using time signal. The control unit determines the sequence in which
computer programs and instructions are executed. Things like processing of
programs stored in the main memory, interpretation of the instructions and
issuing of signals for other units of the computer to execute them. It also
acts as a switch board operator when several users access the computer
simultaneously. Thereby it coordinates the activities of computer’s peripheral
equipment as they perform the input and output.
Central Processing
Unit (CPU)
The ALU and the CU of a computer
system are jointly known as the central processing unit. You may call CPU as
the brain of any computer system. It is just like brain that takes all major
decisions, makes all sorts of calculations and directs different parts of the
computer functions by activating and controlling the operations.
MICROCOMPUTER SYSTEM
We already learned that in a
basic computer system, a Central Processing Unit (CPU) consists of both ALU and
Control Units. In a microcomputer the
CPU is usually implemented on a single chip, which is the microprocessor. Some system may need several additional chips
to be connected to a microprocessor chip to make the CPU. It is common to refer to the microprocessor
as the MPU (microprocessor unit), since it is the CPU of the microcomputer.
·
Since microcomputer system is
actually a basic computer system, the main elements of the internal constructions
and function are similar. However, the
following outlines some important features in mode specific manner of a
microcomputer system as a comparison to the basic computer system.
a) CPU (Central
Processing Unit)
·
A silicon chip that works as
‘heart’ of the computer.
·
Receive instructions from memory
to implement a task.
b) Memory Unit.
·
Store data and programs.
·
Divided into two (2) main
categories:
1) Primary Memory:
ROM (Read Only Memory)
·
Data can only be read but cannot
be written into it.
·
The stored data will not
disappear when the power supply is disconnected.
2. Secondary Memory:
·
RAM can only keep data in
temporary basis, thus we need a permanent storage, which is also called secondary storage.
·
The example of secondary storage
are floppy disc and hard disk. Another
type is CDROM (Compact-disc ROM), which can store up to 600 million characters
and it is suitable for storing huge size of information.
C) Input/Output (I/O)
Unit
·
I/O unit contains the interface
circuits needed to allow the peripheral to proper communicate with the rest of
the computer.
·
In some cases these interface circuits are LSI
chips designed by the MPU manufacturer to interface the MPU to a variety of I/O
devices. In other cases the interface
circuits may be as simple as buffer register.
·
I/O unit allows user (external
environment) to communicate with the computer system via interface unit that
connected to the peripheral devices. The
peripheral devices such as keyboard, printer, sensor that measuring vehicle
speed etc.
·
The port size of I/O unit is
equivalent to the data bus size of the microprocessor.
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