UNIT 1
Computing Devices,Software and
Operating System
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What are the Advantage and Disadvantage of Networking?
Advantage of Networking
1. File Sharing: Networks offer a quick and easy way to share files directly. Instead
of using a disk or USB key to carry files from one computer or office to another,
we can share files directly using a network.
2. Software Cost and Management: Many popular software products are available
for networks at a substantial savings in comparison to buying individually
licensed copied for all of our computers. We can also load software on only the
file server which saves time compared to installing and tracking files on
independent computers. Upgrades are also easier because changes only have to be
done once on the file server instead of on individual workstations.
3. Security: Specific directories can be password protected to limit access to
authorized users. Also, files and programs on a network can be designated as
"copy inhibit" so we don’t have to worry about the illegal copying of programs.
4. Resource Sharing: All computers in the network can share resources such as
printers, fax machines, modems, and scanners.
5. Communication: Even outside of the internet, those on the network can
communicate with each other via electronic mail over the network system. When
connected to the internet, network users can communicate with people around the
world via the network.
6. Flexible Access: Networks allow their users to access files from computers
throughout the network. This means that a user can begin work on a project on
one computer and finish up on another. Multiple users can also collaborate on the
same project through the network.
Disadvantage of networking
1. Security Issues
One of the major drawbacks of computer networks is the security issues
involved. If a computer is a standalone, physical access becomes necessary for
any kind of data theft. However, if a computer is on a network, a computer
hacker can get unauthorized access by using different tools. In case of big
organizations, various network security software’s are used to prevent the theft
of any confidential and classified data.
2. Rapid Spread of Computer Viruses
If any computer system in a network gets affected by computer virus, there is a
possible threat of other systems getting affected too. Viruses get spread on a
network easily because of the interconnectivity of workstations. Such spread can
be dangerous if the computers have important database which can get corrupted
by the virus.
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3. Expensive Set Up: The initial set up cost of a computer network can be high
depending on the number of computers to be connected. Costly devices like
routers, switches, hubs, etc., can add up to the bills of a person trying to install a
computer network. He will also have to buy NICs (Network Interface Cards) for
each of the workstations, in case they are not inbuilt.
4. Dependency on the Main File Server:
In case the main File Server of a computer network breaks down, the system
becomes useless. In case of big networks, the File Server should be a powerful
computer, which often makes it expensive.
What do we mean by transmission media?
Transmission media is the means or pathway by which data is transmitted and received
from one computer to another computer.
There are two types of transmission media, they are:1) Guided media
2) Unguided media
1) Guided Media: - Guided media is such type of media by which data/information is
sent and received through some end to end connection like wire.
Example:- Twisted pair cable, coaxial cable, optical fiber cable
2) Unguided Media: - Unguided media is such media by which data/information is sent
and received through some frequency or some wave like radio wave, satellite etc
Wireless communication: - Communication with the help of unguided media is called
wireless communication.
a) Twisted pair cable:- It is one of the cheapest and most popularly used communication
media in guided system. In this cable a pair of copper wires is twisted to each other in a
helical path making the same structure as a DNA molecule. The reason for twisting is to
reduce electrical interference. It is mostly used telephone systems. These cables are
available in varieties of grade level called levels. Level 5 cables is most expensive but has
bandwidth (100 mbps), level 4 cable has 20 mbps bandwidth and level 3 has 16 mbps
bandwidth.
There are two types of twisted pair cable, they are:A) Shielded twisted pair (STP)
B) Unshielded twisted pair (UTP)
b) Coaxial Cable: - It is the most popular cable which is being used in TV in our homes.
A coaxial cable consists of a thick copper wire in the core, surrounded by an insulating
plastic with a net of thin copper wires used as earthing and in the outermost part it is
insulated by a thick plastic cover. Generally it comes in two categories.
-thin coaxial cable
-thick coaxial cable
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Thick coaxial cable has 100base5 bandwidth which means 10-100mbps
bandwidth with distance 500 m. thin coaxial cable has 10base2 bandwidth which means
10-100 bandwidths with distance 100-200m. It is better than twisted pair cable and has
high bandwidth but expensive in comparison to twisted pair cable.
c) Fiber optics cable/ Optical fiber: - It is the most advanced media in communication.
It has the highest bandwidth 100baseFX (which means 100 mbps with distance 2000m)
and 1000baseLX (which means 1000mbps with distance 3000m) and has highest speed
and is most expensive media in comparison to any other media. It uses light rather than
electricity to transmit information. It is very thin media which is measured in microns and
is very hard to identify with our necked eye. It has two layers-clad and core. Both the
clad and core are made up of same material (glass and plastic). The light is passed
through an optical fiber by the process of total internal reflection. Light source for it is
‘Laser’ or ‘Led’ and detector id ‘Pin’. At the source, electrical pulses generated by
computer or electronic devices, is converted into light by ‘Laser’ or ‘Led’ which flows
from fiber optics in the form of light. At the destination, the light rays are again converted
into electrical pulses by ‘Pin’. It doesn’t have any danger of leakage and electrical
interference. So it can be used in any environments like under big factories, grounds or
airports .It has the highest bandwidth and the highest speed in comparison to any other
media and is most expensive than other media.
Satellite: - Satellite acts as relay station for communication signals. The satellite accept
data and signals transmitted from an earth station, amplifies them and then retransmit
them to another earth station.
History of Internet
The US department of defense laid the foundation of the internet roughly 30 years ago
with a network called ARPNET (Advance Research Projects Agency Net). During the
1970’s work an ARPANET consisted of connecting the various networks and developing
the necessary internet software. During the early 1980’s the network became known as
the internet and it was during that period that business firms began using it but the
general public started using internet after the development of world wide web in the early
1990’s. In 1993 there were only 130 websites all over the world now there are millions of
websites all over the world.
What is Internet? What are the uses of internet?
Internet is not just like one network, it is a coordinated union of a multitude of networks
all over the world or we can say internet is the world largest computer networking, the
network of networks. Internet is global LAN where millions of computers are connected
to each other. any computer user on internet can contact another user on the internet
anywhere in the world, very much like telephone user communicates with another user
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anywhere in the world. Internet is an information superhighway and has seemingly
compressed the world into a cyber colony. Internet is available to anyone who wants to
use it. A majority of internet users are college students, businessmen, professionals etc
and accessing internet has become a way of life.
Uses of Internet
1. We can exchange e-mail with millions of people with e-mail
address in the internet.
2. We can get information about people, products, organizations
and many other things from the internet.
3. We can get search facilities in the internet (such as- google.com)
by the help of which we can search lots of information regarding
any topic within a second.
4. We can send or receive data files, programs, images, sound, and
animation through the internet from very distant places.
5. We can sell or buy products and services through the interent(
Such as E-commerce, E-business)
6. We can give information about our organization and institution
by launching homepage and keeping in the internet which let the
other people around the world to know.
7. We can conduct surveys; get opinions of people around the
world on particular topics through the internet.
8. We can learn or we can do courses through the internet, we can
give online exam through the internet such as MCSE(Microsoft
Certified System Engineering), OCP (Oracle Certified
Professional) etc
The important thing to realize is that the internet permits almost
anything but our imagination is the only limit.
What are the different types of Networking?
Networking is categorized according to the size of network, speed of data transmission,
distance covered, technology used, architecture used, structure of the network etc. There
are three types of Networking, they are:a) LAN (Local area Network):- A LAN connects network devices over a relatively
short distance. A networked office building, school, or home usually contains a
single LAN, though sometimes one building will contain a few small LANs
(perhaps one per room), and occasionally a LAN will span a group of nearby
buildings.
The media (e.g., wire) used in LAN must be of the same type and the protocol
used in it is generally same. It is simpler and cheaper than any other networking
system. Major advantage of this system is the security provided because no any
outsider’s can’t access the resources of a private network. Major disadvantage of
this system is that it can’t cover more than few kilometers
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b) Metropolitan Area Network - a network spanning a physical area larger than a
LAN but smaller than a WAN, such as a city. When LAN grows and spreads in
area then it becomes MAN. It is called metropolitan network because it is
extended up to a city or a larger geographical area. MAN is typically owned and
operated by a single entity such as a government body or large corporation. In this
system different communication media can be adopted and different types of
protocols can be used. Instead of using guided media (e.g. wire), it can use
unguided media (e.g. wireless media). It has more flexibility than the LAN has
many advantages over LAN but has very high chances of data leakage or security
break.
c) WAN:-It is the network that is extended to a large area (e.g. throughout the world
or even more) and the communication is done through satellite. A WAN is a
geographically-dispersed collection of LANs. A network device called a router
connects LANs to a WAN. In IP networking, the router maintains both a LAN
address and a WAN address. A WAN differs from a LAN in several important
ways. Most WANs (like the Internet) are not owned by any one organization but
rather exist under collective or distributed ownership and management. It is the
combination of many different types of LAN and MAN networks, so it has
massive amount of heterogeneous systems(e.g. operating systems, devices,
hardware, topologies, protocols, transmission media etc). Instead of centralizing
the transmitting devices in a particular location such devices are distributed in
different parts of the world. The largest WAN in existence is internet.
Other types of networking are:



Wireless Local Area Network - a LAN based on WiFi wireless network technology
Campus Area Network - a network spanning multiple LANs but smaller than a
MAN, such as on a university or local business campus.
Storage Area Network - connects servers to data storage devices through a
technology like Fibre Channel.
System Area Network - links high-performance computers with high-speed
connections in a cluster configuration. Also known as Cluster Area Network.
Difference between LAN and WAN
LAN ( Local Area Network
1. LAN are smaller networks, usually
within an office base
2. The distance between the nodes is
limited in LAN, there upper limit of
3 km or less and lower limit of 2m.
3. The data rate speed of LAN
normally operate at 1to 100 mbps
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1.
2.
3.
4.
WAN(Wide Area Network)
WAN, or wide area networks, are
broader geographic networks
WAN can spread throughout the world
covering 1000s of kms
WAN normally operate at the speed of
1 to 4 mbps
In WAN error rate is higher than LAN
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4. In LAN error rate are much lower
in comparison to WAN
5. Transmission media used in LAN
are generally wired media (wireless
LAN also exists such WiFi) using
coaxial cable, fiber optic cable.
6. LANs are owned by single
organization.
7. LAN is operated at low cost
5. WAN uses satellite and wireless media
for transmission media.
6. WAN is owned by multiple
organizations.
7. WAN is operated at high cost
Explain different types of Networking Architecture
There are two types of networking architecture, they are
1) Peer-to –Peer architecture (Point-to Point)
2) Client-Server architecture (Broadcasting)
Peer-to –Peer architecture (Point-to Point):In peer-to-peer architecture, computers are connected individually in pair (one-to-one
connection). When the computer A wants to send message to computer C then it must be
passed through B, when packet reaches to computer B it first of all matches the receiver
address attached with the message to its own address. If it matches, then only accepts the
message otherwise it discards it and forwards to the computer C. When the
communication is being done between any two computers, then other channels remain
free. So, there is not so much problem of traffic. As we have seen that each of the
computers get equal priority and each behave like a server on one time and the same
becomes client in other time.
Client- server architecture:It is also called broadcasting architecture, in this architecture computers are connected to
a central device and communication is done through it. When computer A wants to send
message to computer C then message is sent to the central device. The message is first of
all received by the server and the message is broadcasted by the server. All the computers
attached to the network receive such packet; each of them read the receiver’s address and
compares their own address with the address written on the packet. If it matches, then
only the computer accepts it otherwise the packet is discarded or rejected. So in this case,
computer C address matches with the packet address, so computer C accepts, other
computer discard it. In this architecture server is always fixed which control all other
computers and the communication is done through server. All other computers are called
clients. The big disadvantage of this architecture is high traffic problem created by
broadcasting, because at the time of broadcasting, all the computers remain busy. Its big
advantage is its speed.
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Protocol:
Protocols are the rules of transmission. As we know that for a transmission of
data/information to be successful, each of the devices/computers attached to both ends
must speak the same set of languages, must have same set of devices and same types of
software. But practically it is impossible in this distributed world. To overcome this
limitation, certain set of rules which are common and acceptable by both the parties are
developed which play a role of interpreter between the sender and the receiver, which is
known as protocols.
For example: - TCP/IP, SMTP, HTTP etc
Intranet: Intranet is also network of networks. But it is not public it is private network group
and owned by a particular organization, only those persons who are authorized and
authenticated users of that organization can only use this net.
Intranet is based on internet technology to build information system
with an organization or enterprise. It also uses the same protocols as used by the internet
(HTTP, TCP/IP). It inherits all the features of Internet. It is useful for promoting
business, education etc. If permission is given to access intranet from remote location
then it is termed as extranet.
What is network topology? What are the different types of LAN topology? Explain
ANS: - The physical layer of local area network is called network topology. In other
word network topology is the logical way of explaining how computer are connected to
each other and shows physically how they are linked. The major goal of network
topology is to find out the most economical and efficient way to connect all the users to
the network.
There are all together six types of LAN topology, they are as follows:a) Bus Topology
b) Star Topology
c) Ring Topology
d) Tree Topology
e) Mesh Topology
f) Hybrid Topology
a) Bus Topology: - This is the most popular topology. In this topology a single
cable is connected with each computer. The single cable at the middle of all the
computers is called ‘Bus’ from which other nodes are connected by some
connectors and that node is connected on the LAN port of each computer. In this
topology server is located on either side and a terminator is located on other side
of the bus. It is based on broadcasting architecture
Advantage of Bus Topology
 It is relatively easy to install and extend the network
 If any of the computers in network is down, then other computers can
continue their work
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 It is more flexible because we can connect any number of computers by
using a connector in the bus
 It is not expensive to install
Disadvantage of Bus Topology
 Data traffic is high in this topology because it is based on client/ server
architecture
 Data collision is high
 If the backbone cable fails the entire network is unusuable.
 Finding out fault and troubleshooting is hard
b) Star Topology:In this topology a central connecting device known as ‘Hub’ connects
all the computers in the network to each other, which is connected to a powerful central
computer known as server. It is based on client/server architecture.
Advantage of Star Topology:
 It is flexible because in this topology it is easy to add computer and
remove existing one.
 In this topology it is easy to diagnose fault because of the use of ‘Hub’
 In this topology if any of the computers in the network is down, then other
computers can carry out their functions as usual
Disadvantages of Star Topology
 In this topology if the server or hubs fail it makes the whole system
unavailable.
 In this topology cost of cable is more because all the cable from all the
clients must be connected to the server through hub
 It is based on client/server architecture so in this topology data traffic is
high
c) Ring Topology:In this topology each computer is connected in a circular structure.
Each computer is connected to other two computers in either side. It is based on point to
point or peer to peer architecture
Advantage of Ring topology
 There is no dependence on the central server. So, each computer is capable of
acting as server as well as client.
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 Since data travels in one direction, there is less chance of collision and there is
less chance of data- traffic.
 Every computer has equal access facility to the resources.
Disadvantage of Ring topology
 Failure of any one of the computer on the network makes the whole network
down
 Very hard to find out the errors and troubleshooting
 Non- flexible because adding new computer on the network and removing
existing computer is very hard
d) Tree Topology:
The tree topology arranges computers and links into distinct hierarchical structure
in order to allow greater control and easier troubleshooting. A computer acting as a
server in upper level can act as client in lower lever. It minimizes traffic drastically
because broadcasting is done only within one level. Data and traffic can flow from
up to down or vice versa. If any of the computers is down, then it affects only those
computers which are under its control.
Advantage of Tree topology
 The tree topology is flexible to extend and reduce.
 The failure of the leaf node does not affect the whole network.
Disadvantage of Tree topology
 Failure to any of the hierarchical node will cause the failure to the network
on that node.
 The performance of the root node and other hierarchical nodes will affect
the performance of the network.
 It is not easy to install.
 It is not easy to troubleshoot the network problem.
e) Mesh topology:
Mesh topology arranges all the computers where each of the computers is connected
to all computers .If any of the computer is down then other computer can still
continue to work. It is very much complex and troubleshooting much harder.
Advantage of Mesh topology
 Because of the multiple paths to reach the nodes the failure of any node will
not affect the operation of the entire network.
 There is no traffic problem as it has multiple paths.
Disadvantages of Mesh topology
 It is very complex network and is difficult to find the faults and troubleshoot
problems.
 A lot of network cable is needed, so it is costly.
 It is difficult to install and extend the network.
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f) Hybrid topology:
Hybrid topology is the combination of two or more topologies together. It has
advantages of more than one topologies as well as disadvantages, too
What are the different networking devices? Explain each of them in brief.
ANS:The different networking devices are Hub
 Bridge
 Repeater
 Router
 Modem
Hub:
Hub is a device with multiple ports for connecting different computers on the network.
Usually, each file servers has only one NIC. Therefore, it would be impossible to
connect every workstation directly to the file server. To solve this problem, LANs
use hubs, which are very common networking devices. So, it has the following
properties:
 It operates on Physical layer of OSI model
 It accepts data, amplify them and then transmit
 It is used to split network segments and propagate signals through it.
 It does not need path determination and switching
Its big disadvantage is that it can’t filter network traffic and it imposes limitation to the
number of computer that can be connected
Bridge:
It is a device, which connects different network segments and passes data with the same
communication protocols. It is the connecting device between two or more hubs. Some of
the characteristics are:
 It operates at layer 2 ( Data Link) of OSI model
 It reduces unnecessary traffic problem by controlling broadcasting
 Bridges are more intelligent then hubs because they maintain MAC address tables
in them and forward data looking on it.
 Bridges collect and pass packets between 2 network segments
Repeater:
It is another network connecting device. It increases the distance over which a
network can extend. For example, using a category 5 twisted pair cable, we can send
data up to maximum of 100 meters only without amplification. If data travels beyond
that distance without amplification, then it becomes weaker and after some time the
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signal will be destroyed. A repeater provides solution for such problem. Some of the
characteristics of repeaters are:
 It operates at layer-1 (Physical layer) of OSI model
 It receives signals, amplifies them and sends it.
 If the signals are weakened because of long wire, then repeater can amplify,
clean the signal and we can increase length of cable.
Router:
It is also a type networking device which are used to connect separate network and to
access internet. It is similar to Bridge in many ways
Some of the characteristics of routers are:
 It operates at layer -3 (Network layer).
 Router finds the shortest and the best path to forward data between different
paths available
 It use IP address for accessing and forwarding data packets
 It is just like bridge or hub but provides more functionality and is more
intelligent
Modem (modulator and demodulator):
It is a device that interprets digital and analog signals
enabling data to be transmitted over voice-grade telephone lines. At the source, digital
signals are converted to a form suitable for transmission over analog communication
facilities At the destination, these analog signals are returned to their digital form It is
used in multimedia, networking and internet to transmit data(text ,data ,voice, picture
etc) from copper wire because copper wire can transmit only analog signals but the
signals produced by a computer is digital.
In other words modem is a device which has responsibility of
modulating (coding) the data before transmission and demodulating (decoding) the
same data with the same rule at the receiving end.
Analog and digital signals
A signal is called analog signal if the signal is continuously varying with respect to
time. The example of analog signal is the voice signals, music signals, human voice,
temperature etc. A signal is called digital signal if the signal is discrete or
discontinuous. Digital signals are the language of modern day computers. Digital
signal is represented only by digits that are 1 and 0.The examples of digital signal are
the digitized audio and video signals stored in media such as CD/DVD. The digital
signaling has more advantages than analog signaling. The advantage of the digital
signaling is that it is cheaper than analog signaling and is more tolerant to noise
interference.
Modulation:- Modulation is a technique used in transmission of a signal. It is the
process used to describe how the digital signal is changed so it can be transmitted
across the analogue link. Modulation can be amplitude, frequency or phase
modulation depending on the fact that whether the amplitude, frequency or phase has
been changed.
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Types of modulation:Amplitude modulation:-The modulation which is suitable for low speed
transmission is called amplitude modulation.
Frequency modulation:-The modulation which uses two carrier signals. High
frequency signals for high and low frequency signal for low is called modulation.
Phase modulation:-The modulation that uses a single carrier frequency and alters the
phase of the carrier is called phase modulation.
Define Direction of communication flow
Depending on the direction of flow of signals during the communication, mode of
communication can be divided into three types. They are:-simplex, half duplex
and full duplex.
Simplex communication:- when data flows in only one direction from sender to
receiver, then the communication flow is known as simplex communication. For
example:-radio and television broadcast.
Half duplex Communication:-When data flows in both the direction from sender
to receiver and receiver to sender, but the transmission is one way only at a time,
then the communication flow is known as half duplex communication. When the
sender is transmitting the signal, the receiver can’t transmit back to the source at
the same time. For example:-Talking with friends using landline or mobile phone,
sending fax etc.
Full Duplex Communication:When data flows in both the direction from sender to receiver and receiver to
sender simultaneously then the communication flow is known as full duplex
communication. For example:-email and web chatting etc.
Define protocol. What are the different types of protocol?
Protocol
Protocols are the rules of transmission. In other words protocol is a set of rules which is
used by computer to communicate with each other across the network. As we know that
for a transmission of data/information to be successful, each of the devices/computers
attached to both ends must speak the same set of languages, must have same set of
devices and same types of software. But practically it is impossible in this distributed
world. To overcome this limitation, certain set of rules which are common and acceptable
by both the parties are developed which play a role of interpreter between the sender and
the receiver, which is known as protocols.
The different types of protocols are as follows:a) IP ( Internet Protocol)
b) TCP ( Transmission Control Protocol)
c) UDP (User Datagram Protocol)\
d) HTTP( Hypertext Transfer Protocol)
e) FTP( File Transfer Protocol)
f) SMTP ( Simple Mail Transfer Protocol)
g) Telnet( Terminal Network)
h) POP ( Post Office Protocol)
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a) IP (Internet Protocol):- It is a protocol defined in the internet layer of the
TCP/IP protocol suite. The main task of IP is the best effort delivery of the
packets. It is responsible for moving packet of data from node to node. IP
forwards each packet based on a four byte destination address (the IP number).
The Internet authorities assign ranges of numbers to different organizations. The
organizations assign groups of their numbers to departments. IP operates on
gateway machines that move data from department to organization to region and
then around the world.
b) TCP (Transmission Control Protocol):- It is one of the main protocol of the
internet protocol suite. The function of TCP is the reliable, ordered delivery of
stream of bytes from a program on one computer to another computer. It is
responsible for verifying the correct delivery of data from client to server. Data
can be lost in the intermediate network. It adds support to detect errors or lost data
and to trigger retransmission until the data is correctly and completely received.
c) UDP (User Datagram Protocol):-It is one of the core members of the Internet
Protocol Suite, the set of network protocols used for the Internet. It is a simple
OSI transport layer protocol for client/server network applications based on
Internet Protocol (IP). UDP is the main alternative to TCP and one of the oldest
network protocols in existence, introduced in 1980. It is often used in
videoconferencing applications or computer games specially tuned for real-time
performance. It is useful in applications where reliability is not a major concern
but speed is a major concern.
d) HTTP (Hypertext Transfer Protocol):- It is one of the popular application layer
protocols which specify the rules for the interlinked documents called hypertext
documents which contain text images, videos and other multimedia contents.
HTTP is the foundation of data communication for the World Wide Web. The
standards development of HTTP has been coordinated by the Internet
Engineering Task Force (IETF) and the World Wide Web Consortium (W3C).
The HTTP protocol is designed to permit intermediate network elements to
improve or enable communications between clients and servers.
e) FTP (File Transfer Protocol):- It is a reliable and secure file transfer protocol
which requires user to log into the system before file transfer. It helps us to upload
the files to the websites which we are maintaining. Transferring a file require two
participants – FTP client program and FTP server program. FTP client program
run in our computer and FTP server program run on the server computer.
f) Telnet (Terminal Network):-Telnet is the internet tool or protocol that let us
travel from our own workstation out into cyberspace to land on another computer.
Telnet is useful for the remote administration of internet hosts over the internet.
g) SMTP (Simple Mail Transfer Protocol):- It is specified for outgoing mail from
one email server to another. The SMTP is extended to send other type of
information such as text, picture, and video and other multimedia program and
data files.
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h) POP (Post Office Protocol):- It is used to receive email from a remote mail
server. It is designed to support offline mail processing. Using POP mail is
delivered to a central server and the user uses a mail program like Eudora,
outlook, Netscape Messenger etc that connects to the server and downloads all of
the new emails to the users own computer.
Operating System
How do you define operating system? What are the different functions of operating
system?
Ans: - Operating System is an organized set or collection of software programs that
control the overall operation of the computer system.
In other word operating system is a program which controls the
hardware and establishes the coordinated relationship between hardware and other
software
We can also say operating system is a system oriented software
programs which acts as an interface between a user and the hardware (i.e. all computer
resources)
An operating system control the way in which the computer system
functions. The operating system performs the following function:1) It provides the platform to install application software into the computer
2) It co-ordinates or control the input and output devices such as monitors, printers ,
disk drives
3) Protect data, hardware and software from improper use
4) It raises the interrupt and handle the interrupt as and when requires
5) It provides access to compilers or interpreters to translate programs from high
level language into machine languages
6) It manages the memory carefully. The part of the operating system that manages
the memory is called memory manager.
7) It manages the resources efficiently (for example hard disk, printer)
8) It provides long term storage of user information in the form of files and folders
by creating table of each file and folders in the storage device. For example FAT
in DOS, NTFS in Windows and ext3 in Linux.
9) It maintains authority over files by allowing different types of access permission
and priority.
10) It provides a continuous job processing sequence by scheduling and loading of
programs and sub programs.
11) It loads different jobs into the memory in a very efficient manner using a paging
mechanism
12) It provides data security so that one program isn’t allowed to capture the program
or data space of other program. (For that it maintains the boundary of each job in
the memory and each jobs are allowed to run only in that boundary)
13) It interprets commands and instructions given by the user.
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14) It records the entire event that happen in the computer system which is useful for
tracing the past records and troubleshoot (problem detection and correction) if
something goes wrong known as event logging.
What is the difference between GUI and CUI (command user interface or text based
interface or control user interface) Explain the advantage of GUI over text based
interface
Ans:- Graphic user interface is defined as the interface of computer with users which
provides the users with facilities of pull down menus, pointing devices, drag and drop
features, clicking and double clicking of mouse, taskbar buttons , check box buttons ,
multimedia facilities etc . In graphic user interface user can select and run the program by
using mouse pointer, copy files and folders from one location to another location simply
by dragging and dropping and interaction normally take place with the help of dialogue
boxes
For example: Window ( Window 95, Window 98 , Window ME , Window 2000,
Window XP, and the latest one Window Vista )
Command User interface (Control user interface): It is defined as the interface in
which the user must interact with computer by typing command in the keyboard
Example:- MS- DOS
Advantage of GUI over Text Based Interface
Graphic User Interface(GUI)
CUI ( Command User Interface or Text
Based Interface or Character User
Interface)
1) The appearance of GUI is very
attractive
2) It is more efficient than CUI
3) In GUI we can work with pointer
and pointing device which is much
easier
4) It is easier to remember the graphic
symbol
1) The appearance of CUI is not
attractive
2) It is not as efficient as GUI
3) In CUI we must enter or type the
command using Keyboard so we
must remember all the commands
4) It is almost impossible to know or
remember all the command of CUI
5) It is easier for new user to work in
GUI
6) In GUI we can have a facilities of
multimedia and internet
5) It is very difficult for new user to
work in CUI. They have to
remember all the commands which
is much more difficult
6) In CUI we don’t have a facilities of
multimedia and internet
7) In GUI every interaction is done
7) In CUI every interaction is done
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through dialog boxes
8) In GUI we can have DOS program
9) GUI supports multiprogramming
facilities or In GUI more task can
run simultaneously
10) It is user friendly
11) Require more memory
12) Application written for GUI are
device independent
13) More threat of virus in GUI
14) 9) Example: Window 98, Window
XP etc
through typing commands
8) In CUI we don’t have Window
program
9) CUI does not have
multiprogramming facilities or In
CUI one task run at a time
10) It is not user friendly as GUI
11) Require less memory
12) Application written for CUI are
device dependent
13) No threat of Virus in CUI
14) Example:- DOS,UNIX etc
What are the different types of operating system? Explain each of them in brief.
Ans: - The different types of operating system are as follows:1. single user operating system
2. Multi-user operating system
3. Multitasking operating system
4. Real- time operating system
5. Multiprocessing operating system
6. Timesharing operating system
7. Batch operating system
8. Distributed operating system
9. Networked operating system
1. Single user operating system: - single user operating system is the
one in which one user can work at one time. A single user operating
system provides access to the computer system by a single user at a
time. It another user wants to use the computer he or she must have to
wait till the current use finish the job. Example- DOS
2. Multi-user operating system: - A multi-user operating system is such
system where more than one user use the computer system at one time
access to the computer system is normally provided through network.
example: UNIX, Linux etc
3. Multitasking operating system: - A multitasking operating system is
such system through which we can run more than one task (program)
at once .It means multitasking operating system let the user run more
than one task at once. Suppose we can run word, we can print the
document; we can play the song at one time using such system.
Example :- Window XP, Window 2000, Window vista etc
4. Real-time operating system: - Real time operating systems are those
systems which are used by such program which require very fast
response time. The execution time is the most critical issue in the real
time operating system and they must finish the execution of job within
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pre-defined time-boundary. They are used to control machinery,
scientific instruments and industrial systems. Real time operating
system typically has very little user-interface capability, and no enduser utilities. A very important part of an Real time operating system is
managing the resources of the computer so that a particular operation
executes in precisely the same amount of time every time it occurs In
other word we can say that real time operating system are on-line
system that respond to input immediately which is given by the user.
It is a multitasking operating system that aims at executing real-time
applications. Example:- the program which require real time operating
system to get install and run are missile guiding system, medical
monitoring system , flight simulation system etc
5. Multiprocessing operating system: - Multiprocessing operating
system is such system which runs on the computer having more than
one processor. This operating system simultaneously executes two or
more jobs at single time. It contains two processor so the controlling
mechanism of this operating system is more complex. A
multiprocessing operating system is a computer hardware
configuration that included more than one independent processing
unit. Example- UNIX
6. Time sharing operating system:-This is such type of operating
system in which processor time is divided into small units called time
slices and shared in turn between users to provide multi-access. Time
sharing refers to sharing a computing resource among many users by
multitasking. The idea of multiprogramming was further used in time
sharing system .The operating system is responsible for switching
between the jobs in such a way that every terminal feels that it is
occupying the entire computer resources. Another important concept
in time sharing system is priority, interrupt and input and output
management. Important jobs can be given high priority so as to
execute it fast.
7. Batch operating system:-Batch processing operating system allowed
running only one program at a time. Batch processing operating
system works as series of programs which are held in a queue. The
jobs with similar requirements were batched together and run as a
group is called batch processing. This is one of the oldest operating
system .it was designed in mid 50’s and mid 60’s. In this type of
operating system the job (data +program) is not processed until all the
data is fully input. The jobs are stored in a disk in batch in a queue and
run one or more at one time under the control of the operating system.
A job may wait in a batch queue for minutes or even for hour
depending upon the load on the system. Before it could begin to
execute the job it need to read the deck of the card. (data was punched
in the punched card) So, CPU and the peripherals remained idle most
of the time.
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8. Distributed Operating System: An operating system that manages a
group of independent computers and makes them appear to be a single
computer is known as a distributed operating system. The development
of networked computers that could be linked and communicate with
each other, gave rise to distributed computing. Distributed
computations are carried out on more than one machine. When
computers in a group work in cooperation, they make a distributed
system. Some truly distributed systems have dozens of servers around
the globe. If traffic is high in any server the job is transferred to other
server known as load balancing.
9. Network operating system:-A network operating system (NOS) is a
computer operating system that is designed primarily to support
workstation, personal computer, and, in some instances, older terminal
that are connected on a local area network (LAN). Most of the network
operating system works under the principle of Client-server
mechanism. Client server is a mechanism in which co-operation and
intercommunication between various elements of network takes place
and one machine serves others for various functions. In this operating
system user doesn’t have to sit in front of machine in which he or she
wants to work on. A network operating system provides printer
sharing, common file system and database sharing, application
sharing, and the ability to manage a network name directory, security,
and other housekeeping aspects of a network.
10. Embedded Operating System: Computer system that performs a
dedicated function or is designed for use with a specific embedded
software application is called embedded system such as micro wave
ovens, robots, TV sets, router, digital cameras, washing machine,
mobile phones, ATM machine and other automatic digital equipments
etc.The operating systems designed for being used in embedded
computer systems are known as embedded operating systems. They are
capable of operating with a limited number of resources. They have
some characteristics of real time operating system but also have size
memory and power restrictions that make them special. Unlike, a
desktop operating system, the embedded operating system does not
load and execute application. This means that the system is only able
to run a single application. Examples of such operating system are
Windows CE, Palm OS, Free BSD, Minix3, Window ES, and Router
OS etc.
History of Operating Systems
Operating systems have evolved through a number of distinct phases or generations
which corresponds roughly to the decades.
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The 1940's - First Generations
The earliest electronic digital computers had no operating systems. Machines of the time
were so primitive that programs were often entered one bit at time on rows of mechanical
switches (plug boards). Programming languages were unknown (not even assembly
languages). Operating systems were unheard of.
The 1950's - Second Generation
By the early 1950's, the routine had improved somewhat with the introduction of punch
cards. The General Motors Research Laboratories implemented the first operating
systems in early 1950's for their IBM 701. The system of the 50's generally ran one job at
a time. These were called single-stream batch processing systems because programs and
data were submitted in groups or batches.
The 1960's - Third Generation
The systems of the 1960's were also batch processing systems, but they were able to take
better advantage of the computer's resources by running several jobs at once. So
operating systems designers developed the concept of multiprogramming in which
several jobs are in main memory at once; a processor is switched from job to job as
needed to keep several jobs advancing while keeping the peripheral devices in use.
For example, on the system with no multiprogramming, when the current job paused to
wait for other I/O operation to complete, the CPU simply sat idle until the I/O finished.
The solution for this problem that evolved was to partition memory into several pieces,
with a different job in each partition. While one job was waiting for I/O to complete,
another job could be using the CPU.
Another major feature in third-generation operating system was the technique called
spooling (simultaneous peripheral operations on line). In spooling, a high-speed device
like a disk interposed between a running program and a low-speed device involved with
the program in input/output. Instead of writing directly to a printer, for example, outputs
are written to the disk. Programs can run to completion faster, and other programs can be
initiated sooner when the printer becomes available, the outputs may be printed.
Another feature present in this generation was time-sharing technique, a variant of
multiprogramming technique, in which each user has an on-line (i.e., directly connected)
terminal. Because the user is present and interacting with the computer, the computer
system must respond quickly to user requests, otherwise user productivity could suffer.
Fourth Generation
With the development of LSI (Large Scale Integration) circuits, chips, operating system
entered in the system entered in the personal computer and the workstation age.
Microprocessor technology evolved to the point that it becomes possible to build desktop
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computers as powerful as the mainframes of the 1970s. Two operating systems have
dominated the personal computer scene: MS-DOS, written by Microsoft, Inc. for the IBM
PC and other machines using the Intel 8088 CPU and its successors, and UNIX, which is
dominant on the large personal computers using the Motorola 6899 CPU family.
Disk Operating System
1) DOS (Disk operating system):- DOS is a set of control programs which manages the
computer’s resources and creates a well defined software environment for applications. It
is an operating system which was written to control hardware. Word perfect, LOTUS,
dbase, TURBO C/C++ etc are softwares which run under DOS. There are two types of
DOS commands. They are:a) Internal DOS commands
b) External DOS commands
a) Internal DOS commands:- Internal commands are built in the COMMAND.COM file.
It can be executed from any DOS prompt because each of the internal commands are
memory resident. As long as the computer is running, we are ready to give internal
commands. Example of internal commands are:- DIR, CLS, COPY, REN, DATE etc.
b) External DOS commands: - External commands are on the disk as separate program
files. Therefore they must be read from disk before they are executed. They are
comparatively slower in execution than internal commands. Example of external
commands is: - TREE, FORMAT, LABEL etc.
2) Booting:- Loading of system files into the memory of computer and to initialize every
hardware components of the computer system is called booting. There are two type of
booting. They are:- cold booting and warm booting
i)
Warm boot:- restarting of the computer using reset button, restart
option or ctrl+alt+del key is called warm boot.
ii)
Cold boot:- Starting of the computer from power off state to power on
state is called cold boot. Cold boot can be performed by switching on
the computer.
Algorithm of Booting
Step1: Trun on the computer
Step2: ROM is activated and the BIOS is loaded
Step3: POST (Power on self test)
Step4: Boot records load the initial system files (IO.SYS) into RAM from disk
Step5: Then the computer gets start
File:- A file is a collection of related information. It has a name with the extension that specifies
type of file. Executable files are also called program files and often have extension like .EXE and
.COM. Example: practical.doc where practical is a file name and .doc is an extension.
Directory: - A directory is a table of contents of files, directories and sub- directories. Directory
name may or may not have extension. Directory contains information about all files stored on a
disk. A sub directory is a directory within directory. Number of sub directories can be created on
the disk, but the basic directory on the disk is always the main directory called the root directory
and sub directory can be sub divided into a more sub directories, each divided from its parent
directory by a backslash. Command: DIR, it is use to display files, directories and subdirectories.
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Batch file:- A batch file is a file in which series of DOS commands are saved and they are
executed one after another. A batch file is an unformatted text file that contains one or more
commands and has a .bat or .cmd file name.AUTOEXE.BAT is a file which is executed during
the startup of a computer.
What are the advantages and disadvantages of MS-DOS?
Advantages:
1.
2.
3.
4.
5.
6.
7.
It will run on a much smaller system. (entire OS can be placed in a single modern
ROM chip)
Gives you more "direct" control of the processes.
Because of smaller size it will boot much faster than any windows version.
It is cheap and free if you go on the internet.
Very fast even on a relatively slow machine.
It supports different disk like floppy, hard disk,CD etc
It is single user operating system but can work on Local Area Network using
Novel software
Disadvantages:
1. It is single user, single tasking operating system
2. It does not support advanced application software
3. Very few "new" programs available, therefore you need to be able to write
programs in many cases.
4. Not nearly as fancy in the graphics department.
5. Not compatible with current "browsers" and most internet.
6. It is not so user friendly like windows system and cannot support advance
computer peripheral devices even mouse.
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UNIT 2
Programming Language
(Introduction, Generation of Programming
Language, Flowchart and Algorithms)
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Introduction
A Computer cannot perform any job or task without program. A Computer is a dead
machine without program. So to make it live and working it requires a program. Like
operating system is needed to initiate or boot computer and application software is
needed to perform various tasks.
A program is a set of instruction written sequentially and in a
logical way to tell the computer to do a specific task or to solve a given problem. The
process of developing a program is called programming and the language that is used to
develop the program is called programming language also who does a programming is
called programmer.
The language which is used to have communication between machine and human being
is called programming language.
Programming concept:The thorough understanding regarding the entire process of development of programs
is called programming concept. It includes the overall understanding and application
of different computer programming languages, compiler, interpreter, control
structures program design tools, syntax, semantic, programming techniques and
different stages involved in a program development.
Explain Machine language, Assembly language, High level language with their
advantage and limitation (disadvantage)
Machine language: - The language which is called the language of CPU and which is
written in binary code (composed of 0 and 1) is called Machine language. In this
language computer can understand every instruction only in the form of 0 and 1 . All the
valid computer operation are performed in terms of binary operation
Example: - If we want to write and instruction
“Add 2 and 3 “then we have to write “01100001 (ADD) 00000010 (2) 00000011(3)”
Assembly language:- The language in which program is written in short codes like
ADD, MUL or SUB instead of writing instruction in binary number (0 and 1) is called
assembly language. It is also called low level language. Assembler converts the assembly
language to the machine language to make it understandable by computer hardware
because computer can understand the instruction written only in binary form. It is not
user friendly language. This language is also processor dependent language. A Program
written for Intel processor does not work in Motorola processor. Computer viruses are
mostly written in assembly language
High Level Language: - The languages which are quite similar to written English and
are therefore very easier to use in compare to machine language and assembly language is
called high level language. Program written in high level language is translated into
machine language by a program is called compiler or interpreter (first this program
checks the program’s syntax if it is free from errors translator translates into an
equivalent code). High level languages are machine independent language i.e. the
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program written for Intel processor easily run on Motorola processor. It is very easy to
understand. It is user friendly language. It is a problem oriented language.
Advantage of assembly language
1) Assembly language is easier to understand as compared to machine language
2) It is easier to modify as compared to Machine language
3) Chances of error is less than machine language
4) In Assembly language program execution time is faster than program written
in high level languages
5) It is easier to understand as compared to machine language
6) We do not need to take care of storage location of data and instruction while
writing program in assembly language
Limitation/Disadvantage of Assembly language
1) It is a processor(Machine dependent language )
2) Since it is a Machine dependent language it requires the knowledge of
hardware also while writing program is assembly language
3) There is one to one correspondence between the assembly language and
machine language instruction
Advantage of machine language
1) The program written in machine language does not need any translation
2) Though it is very difficult to write program in machine language but the program
written in machine language runs faster than any other program
Disadvantage/ Limitation of machine language
1) Machine language is machine dependent. The program written for one processor
cannot be run in another processor i.e. a machine code of intel processor doesn’t
work for Motorola processor
2) Machine language has to be written in the form of 1 and 0. So it is very difficult
to do program in machine language
3) Chances of error is high while writing program in machine language
4) It is very difficult to debug the program written in machine language
Advantage of high level language
-
High level language is machine independent language. So it is portable ( ie
program written in one processor easily run on another processor
A program written in high level language is easier to learn because it is similar to
English language
It is user friendly language
Chance of error is less and it is very easy to debug
Programming in high level language requires less time and effort as compared to
low level language.
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Limitation/ disadvantage of high level language
1) The program written in high level language in less efficient as compared to the
program written in assembly and machine language because it require more
memory and more time to execute.
2) The task related to the computer hardware can be programmed or handled only
by either machine or assembly language so for these purposes high level
language cannot be used
Differentiate between compiler and Interpreter
Compiler
i)
ii)
iii)
iv)
v)
vi)
vii)
Interpreter
It translates a complete high level
language program into machine
language at once
It finds the syntax errors after
compiling the whole program
i)
The compiling process is faster
than interpreter.
It creates the object code after
compiling the whole program
iii)
Debugging process is complicated
in compiler
Compiler demands more resources
(memory, CPU time etc) than
interpreter.
Example:- C, C++, Visual Basic,
java etc
v)
ii)
iv)
vi)
vii)
It translates high level language
program into machine language
line by line.
It finds the syntax errors after
translating each line of the
program.
The interpreting process is slower
than compiler.
It creates the object code after
translating each line of the
program.
Debugging process is easy in
interpreter.
Interpreter requires low resources.
Example:- BASIC,
GWBASIC etc.
QBASIC,
What do you mean by 4GL? Give example
Ans: - The language which works at a higher level than normal high level languages such
as COBOL, Pascal, C, and C++ is called 4GL language. These are result oriented
language and have heavy data processing and query capability. 4GL permits programs to
be constructed using short English like easily understood and easily remembered
commands. 4GL programs are also needed to be translated either by compiler or
interpreter. There are inbuilt and ready to use GUI-objects like forms, command buttons,
radio buttons reports etc. 4GL are dedicated for some particular application development.
Example of 4Gl is oracle, MS-SQL, Sybase etc
what are the advantage of 4GL?
Ans: - The advantages of 4GL (Fourth generation language) are as follows:1. One line of 4GL code is equivalent to many lines of 3 GL code
2. System development is faster
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3. Program maintenance is easier because the program source code is smaller
4. Program developed in 4th generation language is more portable than those
developed in 3rd generation languages.
5. Better communication with user with very less effort
6. End user can often develop the program. All the user need to do is click the
button, drag and drop the components etc.
Disadvantage of 4GL are:1. Needs longer time to convert into machine language than other languages.
2. Execution speed is slower than other languages
Define Programming statement. Explain the different types of programming
statement.
Ans:- An instruction or expression ( also called code) written in high level language to do
a specific task in a program is called programming statement. Each programming
statement commands the computer to do some specific task such as input, output,
calculation or some logical decision. One program statement in high level language may
results in several instructions in machine language when the program is compiled.
Programming statement may consists of keyword, variables, operators, control structures,
data type , library function, user defined function etc.
There are three types of programming statement used in program. They are:1. Simple statement:- It is a basic part of program and it is a single
line expression which is used to carry out assignment, calculation
or to test logical decision. Example:X=10 - assign integer values 10 to x variable
a>=50 - logical statement to check whether a is greater than or
equals to 50 or not.
2. Compound statement:-Compound statement is defined as a
statement which consists of two or more individual instruction.
Example:- A= l*b; where one instruction is for multiplication of l
and b and other instruction is for assigning multiplication value to
the variable A.
3. Control Statement:- A statement that affects the flow of execution
through a program is called control statement. Control statements
are also called control structures in high level languages. They are
the basic building blocks of high level languages. There are three
types of control statements. They are:-Sequence, Selection and
Iteration (Repetition).
Define control structures. Explain different types of control structures.
Ans:- The structure which regulate the order in which program statements are
executed are called control structures. There are types of control structure. They
are:Sequence :- It is the set of program instruction which follow one another and are
to be executed unconditionally (not dependent on any program conditions)
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Instructions are put in a predefined sequence (just like a queue in a cinema hall)
and the next instruction is executed by CPU only after the execution of previous
instruction ( C never comes before B)
Selection: It is the set of instructions which are to be executed conditionally that
is they are executed based in condition that can be either true or false. Commonly
used logic for selection are if condition, if else condition, if else if condition and
select case condition
Iteration: - These are the computer instructions which are to be performed
repeatedly and conditionally that is loop statement are driven by the loop
condition. Commonly used logic for iteration are while loop, do while loop and
for loop
Algorithm, Flowchart and Pseudo code
Algorithm: - An algorithm is a sequence of instructions or step by step instruction to find
the solution of a problem. Algorithm should be simple and clear. It must be to the point
and should lead to the solution of the problem in finite number of steps.
In other words the set of rules that define how a particular problem can be
solved in finite number of steps is known as algorithm. An algorithm is composed of a
finite set of steps, each of which may require one or more operations. Each operation
must be definite, effective and finite
A program is the expression of an algorithm in a programming language. Thus, the
success of a program depends upon the algorithm. Therefore the logic of the problem
must be clearly expressed in an algorithm.
In other we can say an algorithm is a collection of finite number of
instructions arranged in a sequence to find the solution of a problem.
Example:
Algorithm for adding the two numbers
Step1: Start the program
Step2: Input number x, y
Step3: Read x, y
Step4: Z←x+y
Step5: Print Z
Step6: Stop the program
Example:An algorithm to go to the cinema and see a movie
Step1: Start the program
Step2: Go to the cinema hall
Step3: Is the ticket counter open?
Step4: If it is not open, return home
Step5: If it is open, buy a ticket
Step6: Get into the cinema hall
Step7: Watch the movie
Step8: Return home
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Step9: End the program
Flowchart:
A flowchart is a pictorial representation of an algorithm. We can also define it as a
program planning tool for organizing the sequence of steps necessary to solve a problem
which is shown in terms of symbols. Flowchart use symbols that has geometrical shapes
to indicate the different operation and these symbols connected by flow lines which
indicate the order of execution of the various activities. It is used by the programmers to
develop the program and system designer to represent the overall system while analyzing
and developing the system.
Example:Flowchart of adding the two numbers
Start
Input X, Y
Read X, Y
Z=X+Y
Print Z
End
Advantage of flowchart
 It is an independent language .so, the flowchart we design for programming in
one language is applicable for programming in another language
 Once the flowchart is prepared it is very easy to do the coding by looking at the
flowchart
 It is very easy to understand the logic of program by designing the flowchart.
Even people who don’t know the coding can understand the logic of program with
the help of flowchart
 Systematic debugging and testing is easily possible with the help of flowchart
 It provide good documentation for organization
 It is useful in debugging the program
 It provides valuable information which cannot be expressed by thousands of
words
 It is user friendly. It can be more easily understood
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 It expresses clearly the logic of a given procedure.
 It is unambiguous as there can be only one direction of logic at any one time
 It is used as working models in the design of a new programs and system.
Disadvantage of flowchart
 Preparing flowchart is a time consuming process
 If there is a change in logic again we have to develop the new flowchart
 Flowchart do not provide any convenient means to highlight the more important
operation
 Flowchart are quite costly to produce and difficult to use and manage
 Complex and detailed charts can be laborious to plan and draw
 The translation of flowchart into computer programs is not easy
 Preparation of flowchart is a very slow process
 Most software developers believe that flowcharts are a waste of time and that
these slow down the process of software development and they do not start the
software development with flowchart, flowchart are only use for the purpose of
documentation
Pseudo-Code:
The general meaning of pseudo code is false code or fake code. Before we
write a real program, we write a program that look like a code on the basis of
algorithm and flowchart, which may not be syntactically correct but looks like
program code is called pseudo code. The instruction of pseudo code is written
by using English phrase and mathematical expression. It has no hard and fast
rules for writing instruction in pseudo code but the instruction are closer to
high level language instructions. The pseudo code designers should have basic
knowledge about high level language before writing pseudo code. It is also
independent of any programming language.
Example:
Pseudo code for calculating area of rectangle
Input length, breadth
Calculate area= length*breadth
Output area
Differentiate between syntax and semantics.
Synatx:The rules that we use while writing code is called syntax. Syntax is the grammatical
rules of writing the programming statement. In other word syntax is the rules that tells us
whether a string is a valid program or not. The error which is detected by the computer if
we violate the rule of writing programming statement is called syntax error.
Semantics:The rule that gives the meaning to programs are called semantics. The error which occurs
in program logic is called semantical error or logical error. The semantical error is not
detected by the computer and the compiler compiles it successfully. We can only see the
error after the program is being executed and give wrong output. So it is very difficult to
find the semantical or logical error. Because no satisfactory method has been found yet to
detect the logical error
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For example:- if we have to find out the sum of two number say x and y but
we subtract the number, then it is called the logical error. Actually the computer assumes
that we are going to subtract but actually we want to find the sum of two number so there
exist an error . So, instead of writing Z=X+Y if we write Z= X-Y, the computer will not
so the error, but the result which we want we will not get.
Let us consider another example: “Ram eats Television “grammatically it correct because
it is in the form of subject + verb object (i.e. syntactically it is correct) but doesn’t
provide any sense. So, this is semantically incorrect
Why it is very difficult to find logical error in comparison to syntactical error?
Ans:- It is very difficult to find out the logical error in comparison to syntactical error
because syntax error violates the rule of writing the programming statement and is
detected by compiler at the time of compiling by showing total error occur in computer
screen but the logical error is not detected at the time of compiling , after it get executed
when we get the wrong output , seeing that wrong output we have to find out the error in
logic. On other hand there is no any satisfactory method has been found through which
we can detect the logical error
For example: - if we have to find out the sum of two
number say x and y but we subtract the number, then it is called the logical error.
Actually the computer assumes that we are going to subtract but actually we want to find
the sum of two numbers so there exist an error. So, instead of writing Z=X+Y if we write
Z= X-Y, the computer will not so the error, but the result which we want we will not get.
What are the symbols used in flowchart. Mention their name with symbol, shape
purpose and description
There are various flowchart symbols that carry different messages and are used for
different purposes. These symbols are shown below:
Symbol
Shape
Purpose
Oval
Start /end
Parallelogram
Input/output
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Description
This symbol
indicates the
beginning or end of
the program. every
flowchart begins
with a start symbol
and ends with a stop
symbol
This symbol
indicates an input or
output operation. It
will appear at any
point where a data is
to be entered into
the computer or at
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times when data is
to be obtained from
the computer
Rectangle
Process
It indicates any
calculation or
manipulation .i.e
processing of data
Diamond
Decision/condition
Line with direction
Flow-line
It is used to check
logical conditions. It
has one entry and
two exit point
which are for true or
false
It is used to indicate
direction of flow of
information.
Circle
Connector
End of page
A
A
Beginning of page
Large bracket with
line
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Comment box
Connectors are used
for the long
flowchart that does
not fit in the same
page. In this
condition the
flowchart can be
broken into parts
and an arrow is
drawn into a
connector symbol
containing a unique
number or letter
Comment box can
be used to indicate
any comments for
better
documentation,
clarity and in case of
explanatory notes
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System Flowchart:A flowchart that gives information about a system is called system flowchart. The system
can be data processing system, production system, reservation system, inventory system,
accounting system, evaluation system. In system flowchart, the information flow from
one section of the organizational unit to another section or form one processing machine
to another. It is drawn by the system designer while developing the new system. It plays a
very important role in analysis and designing of new system. It does not focus on the
process to solve a particular problem. In other words A system flowchart describes the
data flow and operations for a data processing system. The flowchart shows how the data
processing is to be accomplished.
Program Flowchart:The program flowchart describes the sequence of operations and decisions for a particular
program In other words we can say that a diagrammatical or pictorial sequence of
instruction used by a programmer to solve any problem is called Program Flowchart
A flowchart which is used by the programmer to solve a problem is called
program flowchart .It is the detailed program which is shown in the form of picture that
how program processing steps will be performed within the computer to convert input
data into the desired output.
Differentiate between flowchart and algorithm
Flowchart
Algorithm
It is a diagrammatic representation of a It is a finite set of step by step instruction
program
of a program
It takes time because we need to draw the It takes less time to write the steps of
symbol
instruction
To understand the program flow one Simple English language is used to write
should understand the meaning of symbols algorithm, so easy to understand.
Need special knowledge to draw flowchart No need of special knowledge to write
algorithm
Maintaining a flowchart is difficult
Maintaining an algorithm is not as difficult
as compare to flowchart
At a glance, one can understand the It is difficult to understand the program
program flow very easily
flow at a glance
Differentiate between system flowchart and program flowchart
System flowchart
Program flowchart
It gives broad overview of overall system
It gives specific view of control flow of a
program
It shows the data flow of a system
It shows the instruction flow of a program
It is designed by system designer
It is designed by programmer
It consist of different kinds of symbols, one It consist of limited symbols, so it is easy
must have good knowledge to understand
to understand the program flowchart
the flowchart
It does not focus on the process to solve a It focus on the process to solve a particular
particular problem
problem
It diagrammatically shows the elements It diagrammatically shows the elements
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and characteristics of the whole system.
and characteristics of the whole program.
It plays a vital role in analyzing and It plays the vital role in developing, testing
designing the new system
and debugging a new program
Program Debugging
Program debugging is the discovery and correction of programming errors. A program
cannot be 100% correct throughout its life time and a very few programs run correctly for
the first time. So, debugging is an important and time consuming stage of software
development
Debugging is basically done to find
1. Syntax error
2. Semantic error
3. Run-time error
1. Syntax error:- The error which occurs when the instruction of program does not
match the structural rule of the programming language is called syntax error
2. Semantic error: - The error which causes the wrong output due to wrong
calculation or wrong input of data is called semantic error.
3. Run- time error: - The error which appears during the execution or runtime of
program is called runtime error. Such errors appear when the computer is asked to
divide by zero or when the variable is assigned large value which is beyond its
capacity. The run-time error causes the termination of program execution.
Procedures and Program
Procedure is a mechanism of doing or performing job or task in a well suited manner or
in a correct way.
A program is a set of instruction written sequentially and in a logical way to tell the
computer to do a specific task or to solve a given problem.
Structured programming
Structured programming is a subset of procedural programming based on the idea
of modularity, where the entire program is divided into modules. Again, each module is
composed of one or more procedures also called as functions. So, it is also called
modular programming. Example:-C, Pascal etc.It follows top down programming
approach.
Advantages of Structured programming are: It is easier to write even a complex program because of modular
programming technique.
 It is easy to use, test, debug and modify.
 It has only one main function so it is easy to maintain.
 It is easy to learn
 It uses top down approach for program development
 A function written t o perform one task can be used in another program
 It provides various control structures.
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Object Oriented Programming
The programming which gives more emphasis on data that is object (combination of data
and related function) rather than procedures is called object oriented programming
It uses bottom up approach for program development. Nowadays almost all the
programming languages are using object oriented techniques, even scripting languages
are also using this technique such JavaScript. This technique of programming is perfectly
matched with the real world object.
Important features of Object-Oriented Programming are as follows:1) Emphasis is given on data rather than procedures
2) Programs are divided into different groups known as objects
3) Data structures are designed such that they characterize the objects
4) Functions and data are tied together
5) Data is hidden and can’t be accessed by external function
6) Functions are communicated between each other through objects.
7) New data and function can easily be added
8) Follow Bottom up approach
Advantages and disadvantages Object-Oriented Programming:OOP contributes greater programmer productivity Better quality of software and lesser
maintenance cost. The main advantages are:1) Making the use of inheritance, redundant code is eliminated and the existing
class is extended
2) Through data hiding programmer can build secure programs.
3) System can be easily upgraded from small to large systems
4) Software complexity can be easily managed
5) Message passing technique for communication between objects makes the
interfaces description with external system much simpler
6) Code reusability is much easier than conventional programming language
Disadvantage of OOP
1) It demands more computer resources.
2) Requires the mastering in software engineering and programming methodology.
3) Benefits only in long run while managing large software projects
Application areas of OOP
1.
2.
3.
4.
5.
6.
Games
Expert system
Object-oriented databases
Artificial Intelligence
AI and expert systems
Most important areas of application is design of user
interface such as window
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7. Computer based training and educational systems
Scripting language
A high level programming language that is interpreted by another program at runtime
rather than compiled by the computer's processor as other programming languages (such
as C and C++) are. Scripting languages, which can be embedded within HTML,
commonly are used to add functionality to a Web page, such as different menu styles or
graphic displays or to serve dynamic advertisements. These types of languages are clientside scripting languages, affecting the data that the end user sees in a browser window.
Other scripting languages are server-side scripting languages that manipulate the data,
usually in a database, on the server.
Scripting languages become popular because of the development of the Internet as a
communications tool. Example:-PHP, JavaScript, ASP etc
Types of Scripting Language
Client -side scripting language:-The language affecting the data that the end user sees
in a browser window is called client side scripting language. Client-side refers to the side
of end users. So, client-side scripts are programs that is written and attached to HTRML
documents that run on a user’s browser while viewing the documents. Scripts allow
HTML forms to process input as it is entered and the result is displayed by the web
browsers like Mozilla, Opera etc. Example:-JavaScript, VBScript etc.
Server- side scripting language:-The language that manipulates the data, usually in a
database, on the server is called server side scripting language. Server-side scripting is a
web server technology in which a user’s request is fulfilled by running a script directly on
the web server to generate HTML pages. The primary advantage to server-side scripting
is the ability to highly customize the response based on the user’s requirements, access
rights or queries into database. Example:-PHP, ASP etc
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UNIT 3
Word Processor
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Object Linking and Embedding (OLE):-It is a technology developed by Microsoft that
allows embedding and linking to documents and other objects. It allows users to integrate
data from different applications.
Object linking allows users to share a single source of data for a particular object. The
document contains the name of the file containing the data, along with a picture of the
data. When the source is updated, all the documents using the data are updated as well.
With object embedding, one application (referred to as the "source") provides data or an
image that will be contained in the document of another application (referred to as the
"destination"). The destination application contains the data or graphic image, but does
not have the ability to edit it. It simply displays, prints or plays the embedded item. To
edit or update the embedded object, it must be opened in the source application that
created it.
Object Linking and Embedding is a technique used to insert data, it is called
Embedding; if we do want the data to update, it is called Linking.
Example:-If it is linked then when the data in the spreadsheet is changed, that change
will show in the Word document. If it is embedded, then changes in the spreadsheet will
not have any effect on the figures in the Word document.
Differentiate between Object linking and embedding
Embedding
It is the process to
objects(picture,file,vedio etc)
Linking
the It is the process to insert the objects but by
establishing the relation between source
object and working object.
After inserting the objects there is no After inserting the object, we can double
relation between source object and working click over it to go into source place, when
object.
we modify the source object it
automatically modify the working object
It does not have the ability to edit it. It It has the ability to edit it.
simply display, print or plays the embedded
item.
insert
What is macro? What are the uses of macro?
A macro is a series of commands and instructions that we group together as a single
command to accomplish a task automatically.
Uses for macros are:

To speed up routine editing and formatting
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


To combine multiple commands — for example, to insert a table with a specific
size and borders, and with a specific number of rows and columns
To make an option in a dialog box more accessible
To automate a complex series of tasks
Write down the steps for creating macro.
1.
2.
3.
4.
5.
6.
Click the Microsoft Office Button, and then click Word Options.
Click Customize.
Next to Keyboard shortcuts, click Customize.
In the Categories list, click Macros.
In the Macros list, click the macro that we want to change.
In the Press new shortcut key box, type the key combination that we want to
choose.
7. Check the Current keys box to make sure that we aren't assigning a key
combination that we already use to perform a different task.
8. In the Save changes in list, click the option that matches where we want to run our
macro.
9. Click Close.
What is hyperlink? What are the uses of hyperlink?
A hyperlink is a word, phrase, or image that we can click on to jump to a new document
or a new section within the current document. Hyperlinks are found in nearly all Web
pages, allowing users to click their way from page to page. When we move the cursor
over a hyperlink, whether it is text or an image, the arrow should change to a small hand
pointing at the link. When we click it, a new page or place in the current page will open.
A hyperlink is a connection from one slide to another slide in the same presentation or to
a slide in another presentation, an e-mail address, a Web page, or a file.
Hyperlinks are a great way to connect our presentation to other slides, presentations,
documents, and the Web. We can use hyperlinks for the following:





To enable us to jump to other slides quickly
To switch to another presentation
To open another file, such as a Word document or Excel spreadsheet
To display a Web page
To open an e-mail to someone
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