Computer system

Compiled by Instructor Temesgen T

COMPUTER SYSTEM COMPONENTS
• System is a group of components that work together to
attain a common goal.
• computer system is composed of HardwareComponents
(input, processing, memory and output units) and
Software Component (system, and application
software).
• Hardware components are units that are visible (or
physical).
• Software components are non-visible programs,
procedures and associated documentations that make
possible the effective operation of computer system.
• firmware is software integrated into hardware.

2.1. HARDWARE COMPONENTS
• Hardware components are units that are visible (or
physical).
• the hardware of the computer can be divided into:
1. Input Unit constituting the various Input Devices.
2. Output Unit constituting the various Output Devices.
3. Various Components within the CPU (Central
Processing Unit).
4. Memory Unit consisting primary and secondary
memory

Input Devices
• Input Devices are those devices that are required
to translate data that is in human readable form,
into a form the computer can process.
• These devices allow direct interaction between
human and machine.
• Eg Keyboard,mouth,Joystick,touchpad,lightpen,
• Digitizing tablet, touch screen,microphone,digital
camera,scanner and soon

Output Devices
• Output devices are used to receive the results from the
CPU after processing.
• translate the information processed by the computer into a
form that humans can understand.
• Most out put can be divided in to two categories, soft copy
and hard copy.
• Soft copy is what you on the monitor. Soft is temporary,
after you have finished with it there is nothing solid to hold.
• Hard copy can be touched and carried. Hard copy is usually
some form of paper out put or it is printed information.
• E.g. moniter,printer,plotter,speaker and soon

CPU(Central processing Unit)

Cont’d
• The Processor executes the given instructions and
manipulates data into information.
• The Control Unit directs the Instructions in the form of
electronic signals, to the rest of the computer that are
input unit, ALU, memory and output unit.
• The Control unit can be defined as ‘the section of the CPU
that selects, interprets and sees to the execution of program
instructions.’
• The Arithmetic & Logic Unit performs all Arithmetic and
Logical operations and controls the speed of those
operations.
• The ALU can be defined as ‘the part of a computing system
containing the circuitry that does the adding, subtracting,
multiplying, dividing and comparing.’
• E.g.Apple,Intel,alpha micro processors

Memory unit
• Memory can be defined as ‘Descriptive of a device or medium that can
accept data, hold them and deliver them, on demand at a later time.
• Memory classified into two:
• 1.Primary Memory(Main Memory)
• RAM(Random Access Memory)
• If power drops information stored in memory is destroyed. That is, if
power is off, information stored in memory will be destroyed. That is why,
main memories are said to be volatile.
• This main memory is used for storing
• Data - for processing
• Instructions - to process the data
• Results - the processed data.
• Read Only Memory (ROM). Information once stored cannot be modified.
Information stored in this memory can be used only for reading purpose.
That is why, memories are said to be non-volatile.
• 2.Secondary Memory
• The Memory which can store data or information permanently for future use is
called secondary storage devices (secondary memory).

SOFTWARE COMPONENTS
• Computer software is nothing but the step-by-step
instructions given to the computer in the form of
programs or procedures or routines in order to
accomplish any specified task or to process the raw
data and convert it into meaningful information.
• In short the software is nothing but the intelligence of
the computer.
• Software is of two different types as it is, for the
computer and for the user.
• 1.System Software – controls and coordinates the
computer hardware.
• 2.Applications Software – designed to solve a specific
problem

System Software
• System Software manages the computer’s basic
operations, allows the computer to run applications
software and allows the user to interact with the computer.
• System software tells the computer how to interpret data
and instructions; how to communicate with peripheral
equipments like mouse, keyboard, printers etc; and how to
use the hardware in general.
• There are many number of system software. The different
types of system software are:
• Operating Systems
• Device Drivers
• Language Translators
• Utility Programs

Operating System [OS]
• It is system software containing a set of programs
called the supervisor that manages the basic
operations of a computer.
• Flexibility of the computer usage depends on
Operating System.
• Without the operating system loaded into the
computer, all hardware and other software are useless.
• When the computer is switched on the operating
system is automatically loaded into the main memory
or RAM of the computer.
• This process of loading the operating system into the
RAM of the computer is called Booting the computer.

Cont’d
• Basic functions of an Operating System are:
• Input-Output management
• Memory management
• File management
• Job control
• All these function together as a group of
programs known as system programs under the
control of the supervisor yields the computer
operating system.
•

Cont’d
• The operating system has various roles:
• It is responsible for managing allocation of the processor
between the different programes using a scheduling
algorithm.
• It is responsible for managing the memory space allocated to
each application.
• It is responsible for smooth execution of applications by
allocating the resources required for them to operate. This
means an application that is not responding correctly can be
"killed".
• It is responsible for security relating to execution of programs
by guaranteeing that the resources are used only by programs
and users with the relevant authorizations.
• It manages reading and writing in the file system and the user
and application file access authorizations.
• It provides a certain number of indicators that can be used to
diagnose the correct operation of the machine.

Device Drivers
• Each and every device (input or output)
connected to the computer requires relevant
software, which makes the device to
communicate or interact with the CPU.
• Without these device drivers any device
connected to the computer is useless and
cannot be used.
• E.g.keyboard driver,network driver,mouth
driver

Language Translators

Cont’d
• Both these high level language and low level language require
language translators to convert the instructions in the human
understandable form into machine understandable form.
• Compilers and Interpreters are the language translators required
to translate high level language into machine understandable
form.
• These are a computer program that produces a machine
language program from a source program that is usually written
in a high-level language by a programmer. The compiler is
capable of replacing single source program statements, with a
series of machine language instructions or with a subroutine.
• Assembler is the language translator required to translate the
assembly language into machine understandable form.

Utility Programs

Application Software

End of Chapter 2

Computer system

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