Definition of Computer System and Block Diagram of Computer System
Definition
of Computer System:
The integration of different computer parts such as
keyboard, mouse, monitor, CPU etc. to form an entire system to work effectively
and efficiently is called Computer System.
A computer system refers to the fully functional system that
is the integration of both hardware and software. The hardware components of a
computer system are physical components that are tangible such as keywords, mouse,
processor, motherboard, main memory, secondary memory, monitor, printer etc.
whereas the software components are logical components that make physical
components work such as data, information, computer instructions etc.
The major hardware components of a computer system are:
●
Input unit
●
Processor
●
Storage
●
Output unit
Input Unit
It accepts the data or instructions given by the user, and
converts the data and instructions from man -readable to machine -readable
code. Some common input devices include keyboard, mouse, scanner, punched
cards, a teletypewriter, magnetic disk reader etc.
Processor
/Central Processing Unit
Central processing unit (CPU) is the portion of a computer
system that carries out the instructions of a computer program, and is the
primary element carrying out the computer's functions. The central processing
unit carries out each instruction of the program in sequence to perform the
basic arithmetical, logical, and input/output operations of the system. A CPU
built on a single chip is called a microprocessor. Nowadays, microprocessors
are also called processors.
Some of the
primary components of a CPU or microprocessor are given below:
●
Registers
●
Control Unit (CU)
●
Arithmetic and Logic Unit (ALU)
Registers
Registers are the primary memory of the computer system.
They are mainly used to store the data during the time of processing inside the
ALU. The Registers within the CPU are of special purpose temporary storage
locations. The main types of registers are of general purpose and specific
purpose register. The important register within the CPU is Program Counter(PC).
Features of
Registers:
●
They are the fastest computer memory.
●
The storage capacity of the registers is small.
●
They are temporary memories of the computer.
Control Unit
The Control Unit is the brain of the CPU itself. It is
situated inside the processor, and controls overall operations and devices of
the computer. There are two types of control units- the first type is called a
hardwired control unit. Hardwired control units are constructed using digital
circuits, once formed cannot be changed. The other type of control unit is a
micro programmed control unit. A micro programmed control unit itself decodes
and executes instructions by means of executing micro programs.
Functions of
the Control Unit
●
The control unit carries out the controlling operations of
the computer.
●
It performs data processing operations.
●
It sends control signals to various parts of the computer
system for controlling.
●
It gives commands to the input data from the input unit to
the memory unit, and then to the ALU.
●
It transforms results from the ALU to the memory unit to the
output unit.
● It gives command to store the data, instruction and program in memory.
Arithmetic
Logic Unit (ALU)
The Arithmetic Logic Unit carries out as the name suggests
Arithmetic and Logical operations on the data made available to it. Basic
arithmetic functions which an ALU can carry out are an addition, subtraction,
multiplication and division. The logical operation it can carry out is greater
than, equal to, less than etc. Besides these operations, some processors also
support operations which check if particular bits are on or otf. The main
operations are summarized below.
●
It performs the basic arithmetical calculations such as
addition, subtraction, multiplication etc.
●
It performs the logical operations such as comparing greater
than, equal to etc.
Memory Unit
Main Memory
Primary memory or main memory is a volatile memory of the
computer. As soon as a computer starts, the primary memory stores all the
running applications, Operating System (OS), user interface and any others. A
program/application that is opened in primary memory interacts with the system
processor to perform all the application specific tasks. They are directly
accessible to the processor. The primary memory consists of the Random Access
Memory (RAM), which can handle the instructions and data at high speed.
Programs are stored in the main memory while they are being executed. Data is
stored only when power supply is given to the computer.
Properties
of primary memory:
●
It is a volatile computer memory.
●
The storage capacity of the primary memory is smaller than
that of the secondary memory.
●
They are faster than the secondary memory.
●
They store data during the time of processing.
Auxiliary
Memory or Storage
Auxiliary memory is also called secondary memory. They have
slower access rates for greater storage capacity and data stability. The
auxiliary memory holds the programs and data for future use because it is
non-volatile. The early forms of auxiliary storage included punched paper tape,
punched cards, and magnetic drums. The most common forms of auxiliary storage
now are of magnetic disks, flash memory, magnetic tapes, optical discs etc. The
purpose of auxiliary memory is to store a large amount of data for future
references.
●
The storage capacity of auxiliary memory is high.
●
They are slower because they do not directly interact with
the processor.
●
They are less expensive.
●
They store data for future references.
Output Unit:
When the computer completes its processing task, the result
must be conveyed back to the user. The
information from the CPU is converted into an understandable form through the
output devices. The output of the computer can be presented into different ways
such as softcopy(display from monitor) , hard copy(printed from printer) etc.
Some commonly used output devices are monitor, printer, plotter, speaker etc.
