The document provides an overview of computer systems and their components. It discusses the input-process-output cycle that computers follow and describes the main hardware components - the input, processing, output and storage units. It also discusses different types of memory, CPUs and their components. The document then summarizes system and application software, different operating systems including batch, time-sharing, distributed, real-time and network operating systems.

1. Notes by Pankhuri jain
Module 1

2. Computer system
 What is computer system?
 Electronic device
 Performs operations
 According to programs.
 Works on the principle of Input-Process-Output
cycle.

3. Input-Process-Output cycle

4. Components
of a
computer
Hardware
Input
unit
Proce
ssing
unit
Outp
ut
unit
Storage unit
Software
Operating
system Application
Programs

5. Input unit
 Formed by input devices.
List of input devices
1. Keyboard :
• 104 keys
•Used to type letters, digits and
specials symbols
• Has various types of keys like
function keys ,
alphabetical keys , numeric keys
,special keys etc.

6. 2. Mouse 3. Joystick
• pointing device
• works in graphic environment like
windows
• Gives input by selecting and
moving objects on screen.
•Executes command by clicking on
icons, options and menus.
•Types : scroll mouse, optical
mouse, cordless mouse
•Controls movements of objects
on screen.
•Pointing device
•Has a vertical stick and a track
ball at its bottom
•Used for gaming, training
simulators and controlling robots.

7. 4. Scanner 5. Microphone
•Converts printed documents into
images
•Operates in same manner as
Xerox
•Optically reads an image and
covert it into digital signals
•Digital signals are stored as
digital files
•These files can be manipulated.
•Speech input device
•To operate we require
microphone to talk to computer
•Sound card is required which
digitizes audio input into binary
codes

8. 6. Webcam 7.Touch pad
Captures images and
videos on internet.
Pointing device in
laptops which senses
touch and pressure.

9. 8.Touch screen
Many more like : bar code reader , light pen
etc.
Senses human touch , gloved
hand ,pen or any other
pointing device.

10. Processing unit /CPU
 Brain of the computer
 Controls working of entire computer system
 Placed on motherboard inside the CPU tower
 Size = 1.5 inches square (approx.)
 Speed is measured in MHz or GHz and 3 GHz
=3000 MHz roughly.
 It processes the data ,brings instructions from
memory, decodes them and executes them.

11. Components of CPU
1. Control Unit(CU) : controls and coordinates
the various operations of computer system. It
acts like a traffic signal directing the flow of
data in the computers.

12. 2. Arithmetic Logical Unit (ALU) : Performs all
arithmetic and logical functions like-
 Addition
 Subtraction
 Multiplication
 Division
 Logical AND,OR ,NOT
 Increment (addition of 1)
 Decrement

13. 3. Main memory unit (MMU) : The memory unit
is the principal storage of the computer. All the
data and instructions that the computer needs
at a moment are stored here. Any storage unit
of a computer is ranked according to:
 Access time
 Storage capacity
 Cost per bit of storage

14. Fundamental types of memory
1. Primary memory-:
i. Primary Memory also called as volatile memory because the
memory can’t store the data permanently.
ii. Primary memory select any part of memory when user want to
save the data in memory but that may not be store
permanently on that location.
iii. It is embedded with two types of memory :- RAM(Random
Access Memory) & ROM(Read Only Memory).
iv. It is accessed directly by the processor.
v. It is the fastest memory available.
vi. It is costlier as compared to secondary memory.

15. TYPES OF PRIMARY
MEMORY
 Random-access
memory, or RAM, is a
form of data storage that
can be accessed randomly
at any time, in any order
and from any physical
location in contrast to other
storage devices, such as
hard drives, where the
physical location of the
data determines the time
taken to retrieve it. RAM is
measured in megabytes
and the speed is measured
in nanoseconds and RAM
chips can read data faster
than ROM.
 Read-only memory,
or ROM, is a form of data
storage in computers and
other electronic devices
that can not be easily
altered or reprogrammed.
ROM can only be read by
the processor. Data to be
stored into ROM is written
during the manufacturing
phase itself. ROM is
slower and hence cheaper
than RAM. It retains its
data even when power is
switched off, i.e. it is non-
volatile.

16. Types of RAM
 Static RAM (SRAM)
 Static RAM stores
the data only as long
as the power supply
is on.
 Static RAM
consumes more
power and it is
costlier.
 The speed of S-Ram
(Static RAM) is
higher than D-(RAM)
 Dynamic RAM
(DRAM)
 Dynamic RAM loses
its data in a very
short time.
 It is made of millions
of transistors and
capacitors

17. Types of ROM
 PROM (Programmable Read Only Memory)
can be programmed only once by a special
device and uses high voltages.
 EPROM (Erasable Programmable Read Only
Memory) can be rewritten using UV radiation.
 EEPROM (Electrically Erasable
Programmable Read Only Memory) an be
rewritten electrically and such devices do not
require to be removed from the computer.

18. Fundamental Types of Memory
2. Secondary/ auxiliary memory :-
i. Auxiliary memory also known as auxiliary
storage, secondary storage, secondary
memory or external memory.
ii. It is a non-volatile memory (does not lose stored
data when the device is powered down) that is not
directly accessible by the CPU, because it is not
accessed via the input/output channels (it is an
external device).
iii. It is used to store a large amount of data at lesser
cost per byte than primary memory;
iv. It is less expensive than primary storage.
v. The most common forms of auxiliary memory
are flash memory, optical discs, magnetic
disks and magnetic tape .

19. Output unit
 Formed by output devices.
List of Output devices
1. Monitors- There are two kinds of
viewing screen used for monitors :
 Cathode-Ray Tube (CRT)
Monitor :-The CRT display is made up of
small picture elements called pixels. The smaller
the pixels, the better the image clarity or
resolution. It takes more than one illuminated pixel
to form a whole character, such as the letter ‘e’ in
the word help. There are some disadvantages
of CRT −
 Large in Size
 High power consumption

20. Output devices
 Flat-Panel Display
Monitor:-
The flat-panel display
refers to a class of video
devices that have
reduced volume, weight
and power requirement
in comparison to the
CRT. You can hang
them on walls or wear
them on your wrists.
Current uses of flat-
panel displays include
calculators, video
games, monitors, laptop
computer, and graphics
display.

21. Output devices
2. Printers- It is an output
device, which is used
to print information on
paper. There are two
types of printers −
 Impact Printers :-
Impact printers print
the characters by
striking them on the
ribbon, which is then
pressed on the paper.
 Eg. : Dot – Matrix
Printers, Line
printers.
 Non-impact
Printers : These
print the characters
without using the
ribbon. These
printers print a
complete page at a
time, thus they are
also called as Page
Printers.
 Eg. : Laser Printers ,
Ink-jet printers

22. Output devices
3. Speakers – These
are attached to
computers for the
output of sound.
Sound cards are
required in the
computer for
speakers to function.
Speakers range from
simple, two-speaker
output devices to
surround-sound multi-
channel units.

23. Types of computers
1. Micro computers :
 Cheapest
 Widely used
 Fastest growing
 Small
 Microprocessor as CPU
 specially designed for general usage like
entertainment, education and work purposes.
 Example - Desktop computers, Gaming consoles,
Sound & Navigation system of a car, Netbooks,
Notebooks, PDA’s, Tablet PC’s, Smartphones,
Calculators

24. 2. Minicomputer :
 Used by small businesses & firms.
 Called as “Midrange Computers”.
 These are small machines and can
be accommodated on a disk with not as processing
and data storage capabilities as super-computers &
Mainframes.
 Are multi-user systems.
 Terminals are attached to central computer.
 less powerful than a mainframe or supercomputer,
but more expensive and more powerful than
a personal computer.
 Example : TI-990, IBM system/3

25. 3. Mainframe computers:
 Can store huge amount of data.
 They are large in size and memory, power and
expensive.
 Support time sharing and virtual memory.
 Can be accommodated in large air-conditioned
rooms because of its size.
 Universities, banking institutions, stock exchanges,
insurance companies are some examples of using
mainframe servers.
 Examples - IBM zSeries, System z9, System z10
servers

26. 4. Supercomputer :
 Most powerful computers in performance and
processing.
 These computers are used for research and
exploration purposes, like NASA uses
supercomputers for launching space shuttles,
controlling them and for space exploration
purpose.
 Are very expensive and very large in size.
 It can beaccommodated in large air-conditioned
rooms.
 Examples - K-202, Texas Instrument TI-990,
SDS-92

27. SOFTWARE
 Set of programs that are stored in the
computer.
 Intangible component
 Types of software:
 System software
 Application software

28. System software
 collection of programs
 operates, controls, and extends the processing
capabilities of the computer itself.
 prepared by the computer manufacturers
 Programs are written in low-level languages,
which interact with the hardware at a very basic
level.
 serves as the interface between the hardware and
the end users.
 Examples: Operating system, device drivers,
server, utilities etc.

29. Application software
 All software applications prepared in the computer lab
can come under the category of Application software.
 Designed to allow the user of the system complete a
specific task or set of tasks.
 May consist of a single program, such as Microsoft's
notepad for writing and editing a simple text. It may also
consist of a collection of programs, often called a
software package, which work together to accomplish a
task, such as a spreadsheet package.
 Example – Microsoft word , PowerPoint , Income tax
software , Railway reservation software.

30. Difference between System Software and
Application Software
1. This is used for operating
computer hardware.
2. These are installed on the
computer when operating
system is installed.
3. In general, the user does not
interact with system software
because it works in the
background.
4. These can run independently. It
provides platform for running
application softwares.
5. Examples- compiler,
assembler, debugger, driver,
etc.
1. This is used by user to perform
specific task.
2. These are installed according
to user’s requirements.
3. In general, the user interacts
with application sofwares.
4. These can’t run independently.
They can’t run without the
presence of system software.
5. Examples - word processor,
web browser, media player,
etc.
System software Application software

31. Operating system
 An operating system, is a:
 product,
 software type,
 part of a system, equipment or computerized
equipment,
 Acts as interface between hardware and user,
 deals with management and coordination of its
activities.
 plays the role of host for all applications running
on the equipment (hardware).

32. Functions of an OS
1. Process management – Handles the
creation and deletion of processes ,
scheduling and synchronization of
processes.
2. Memory management – Handles
allocation and deallocation of memory
space as required by various programs.
3. User interface – provides interface
between the user and hardware.

33. 4. File management – responsible for creation
and deletion of files and directories.
5. Device management – manages different
devices connected as well as detects device
failure and notifies same to the user.
6. Security management – protects resources
and information against destruction and
unauthorized access.

34. Types of operating system
1. Batch operating system
 The users of a batch operating system do not
interact with the computer directly.
 Each user prepares his job on an off-line device like
punch cards and submits it to the computer operator.
 To speed up processing, jobs with similar needs are
batched together and run as a group.
 The programmers leave their programs with the
operator and the operator then sorts the programs
with similar requirements into batches.

35. Batch operating system
(continue)
The problems with Batch Systems are as follows
−
 Lack of interaction between the user and the
job.
 CPU is often idle, because the speed of the
mechanical I/O devices is slower than the
CPU.
 Difficult to provide the desired priority.

36. Types of operating system
2. Time-sharing operating systems
 Time-sharing is a technique which enables
many people, located at various terminals, to
use a particular computer system at the same
time.
 Time-sharing or multitasking is a logical
extension of multiprogramming.
 Processor's time which is shared among
multiple users simultaneously is termed as time-
sharing.
 Multiple jobs are executed by the CPU by
switching between them, but the switches occur
so frequently. Thus, the user can receive an

37. Time-sharing operating systems
(continue)
Advantages of Timesharing operating systems
are as follows −
 Provides the advantage of quick response.
 Avoids duplication of software.
 Reduces CPU idle time.
Disadvantages of Time-sharing operating
systems are as follows −
 Problem of reliability.
 Question of security and integrity of user
programs and data.
 Problem of data communication.

38. Types of operating system
3. Distributed operating System
 Distributed systems use multiple central
processors to serve multiple real-time
applications and multiple users. Data processing
jobs are distributed among the processors
accordingly.
 The processors communicate with one another
through various communication lines (such as
high-speed buses or telephone lines).

39. Distributed operating System
(continue)
The advantages of distributed systems are as
follows −
 With resource sharing facility, a user at one site
may be able to use the resources available at
another.
 Speedup the exchange of data with one another
via electronic mail.
 If one site fails in a distributed system, the
remaining sites can potentially continue operating.
 Better service to the customers.
 Reduction of the load on the host computer.
 Reduction of delays in data processing.

40. Types of operating system
4. Real Time operating System
 A real-time system is defined as a data processing system in
which the time interval required to process and respond to
inputs is so small that it controls the environment.
 The time taken by the system to respond to an input and
display of required updated information is termed as
the response time
 Real-time systems are used when there are rigid time
requirements on the operation of a processor or the flow of
data and real-time systems can be used as a control device
in a dedicated application.
 A real-time operating system must have
 well-defined, fixed time constraints, otherwise the system will
fail. For example, Scientific experiments, medical imaging
systems, industrial control systems, weapon systems, robots, air
traffic control systems, etc.

41. Real Time operating System
(continue)
There are two types of real-time operating systems:
1) Hard real-time systems- guarantee that critical
tasks complete on time. In hard real-time
systems, secondary storage is limited or missing
and the data is stored in ROM. In these systems,
virtual memory is almost never found.
2) Soft real-time system- are less restrictive. A
critical real-time task gets priority over other
tasks and retains the priority until it completes.
Soft real-time systems have limited utility than
hard real-time systems. For example,
multimedia, virtual reality, Advanced Scientific
Projects like undersea exploration and planetary
rovers, etc.

42. Types of operating system
5. Network operating System
 A Network Operating System runs on a
server and provides the server the capability
to manage data, users, groups, security,
applications, and other networking functions.
The primary purpose of the network
operating system is to allow shared file and
printer access among multiple computers in
a network, typically a local area network
(LAN), a private network or to other
networks.

43. Network operating System
(continue)
The advantages of network operating systems are as
follows −
 Centralized servers are highly stable.
 Security is server managed.
 Upgrades to new technologies and hardware can be
easily integrated into the system.
 Remote access to servers is possible from different
locations and types of systems.
The disadvantages of network operating systems are as
follows −
 High cost of buying and running a server.
 Dependency on a central location for most operations.
 Regular maintenance and updates are required.

44. Types of operating system
6. Standalone operating system
 It is independent of another.
 Computer is not a part of any other
network,typically LAN.
 It is configured in such a way that all
unnecessary ports/services that can allow
access to the computer are blocked.
 Generic OS

45. Advantages of standalone OS
 Damage control
 Simplicity
 Convenient
 Doesn’t affect any other user.

46. Disadvantages
 Restriction to one computer
 New programs has to be set up one by one
 Costlier
 Hard to monitor.