2. Software:
The set of instructions that tells the computer what to do is called the
computer software or program the user will need to have application
software such as word processor, graphics design software, a game or a
Web browser.
The User Interface:
To enter data or program instructions, to request that a file be saved or
printed, or simply to view the information that has been produced the user
will need a user interface.
Types of User Interface:
1) Command-based interface: When using a command-based interface
such as MS-DOS, the user has to remember (or look) up a variety of
commands and their various options or parameters, making it difficult
for novice users to operate.
2) Menu-driven Interface: A menu-driven user interface allows the user to
select from a menu, a predefined list of available options or selections.
This is already an improvement on the command-driven interface, since
the user no longer has to rely on memory to remember the available
options or commands.
3) Graphical User Interface: The graphical user interface (GUI) is currently
the most popular interface on PCs. It requires a high-resolution graphics
monitor. Active applications will have their own window, which can be
re-sized at will, often overlaying windows of other applications.
4) Pen-based Interface: Pocket computers and handheld computers are
generally too small to incorporate a keyboard. Instead, many combine
the liquid crystal display (LCD), which is the output screen, with a
pressure sensitive layer that can be used for input. All user input
happens by means of a pen-like pointing device.
5) Natural Language Interface: Voice input and output based on a limited
set of stored sounds is readily available across all computer platforms,
and is widely used by the visually impaired, and for hands-free data
input.
Application Software:
 General purpose applications assist a wide variety of users with
common information processing tasks such as word processing, web
browsing, electronic mail, and scheduling or data management.
 Business applications aim to automate common, generic business
functions or processes. They include debtors, creditors, general
ledger, inventory management, and sales processing.
 Scientific applications are focused on the needs of scientists and
researchers: astronomy, weather forecasting, geographical
information systems (GIS), statistics, simulations, engineering
drawings, etc.
 Finally, there is a large category of applications that do not fit in any
of the above categories, such as computer-based training software or
games.
Programming languages:
The systems are developed by means of programming languages:
artificially constructed languages to code the instructions for a computer.
These languages have their own vocabulary, grammar (syntax), constructs
and have often been designed to meet the demands of developing certain
types of applications. Let us look at the various types of programming
languages.
 First generation: machine Language: The lowest level in which
programs can be written is machine language (ML). This is the binary
code that can be interpreted directly by the CPU.
 Second generation: assembler language: The development of
assembler languages represented a big improvement by replacing the
binary code with symbols that are easier to remember.
 Third generation procedural languages: Many different 3GLs have
been developed during the 60s and 70s. Some of the more successful
ones were BASIC (“Beginner’s All-Purpose Instruction Code”), COBOL
(“COmmon Business Oriented Language”), FORTRAN (“FORmula
TRANslation language”), and many more.
 Object-oriented languages: The first step in developing an objectoriented application is to identify suitable objects. These can be
physical entities such as an employee; or they could be informational
entities such as report.
Operating System:
The operating system is an essential piece of software that resides on
every computer. It allows the computer to run a number of different
applications, and shares resources such as printers between a numbers of
different users.
3. Networks & Internet:
When a numbers of computers are connected together, they form a
computer network.
Networks according to size:
 Personal Area Network (PAN): consists of two to five computing
devices. This found in the home, and may be based on wireless
technology like Bluetooth.
 Local Area Network (LAN): the most common type of network. It
consists of from about four up to as many as a couple of hundred of
computers linked together with one set of cables, usually within the
same building. Most LANs are controlled by a central fileserver that
takes care of network communications, security control and the storage
of data files. A student computer laboratory typically constitutes one
LAN.
 Metropolitan Area Network (MAN): a network infrastructure linking
various local businesses within a large city area. This is now almost
completely superseded by the Internet.
 Wide Area Network (WAN): the opposite of the LAN. It links computers
over large geographical areas. This network usually makes use of the
public telecommunications network.
Network Topologies
The network topology refers to the physical and logical way in which the
computers in a network are connected together.
 The star network is driven by one central computer to and through
which all other computers communicate. Although this allows for
central co-ordination and control, it requires a very reliable central
computer and lots of cables.
 The ring network consists of a continuous loop connecting all
computers. Signals travel in a given direction and all computers have
equal access to the data.
 The bus network is currently the most popular configuration. A central
data cable is used, to which each computer (and other devices such as
printers and routers) can be attached. Devices can be added or
removed without affecting the rest of the network.
Network Devices:
1. Network cables are the physical wires by which computers are linked
together. The most common types are: Twisted pair, Coaxial cable, fiberoptic. But not all computer devices need a physical cable connection.
Because of the cabling costs, engineers have explored many methods of
transmitting data without the use of wires this called Wireless.
2. Network interface cards (NICs) are necessary when computers are
connected directly to other computers by means of digital network
cables. Their primary function is to make sure that there is no
transmission conflicts with the other computers linked to the network.
In addition, the network card usually fulfills an error-checking function,
to ensure that uncorrupted data is received at its destination.
3. Multiplexers allow a single channel to carry data transmissions from
many sources, by merging them at one end of the channel and then
separating the individual transmissions at the receiving end of the
channel.
4. Routers A hardware device designed to take incoming packets, analyzing
the packets and then directing them to the appropriate locations.
5. Modem allows a computer to communicate with another computer by
means of the public voice telephone network, rather than by using
digital cabling. This requires the conversion of digital computer signals
into analogue sound signals this process is called modulation. At the
other end of the line, these sound signals are converted back into digital
signals – or demodulated. The word modem refers to this modulation /
demodulation process.
What is the Internet?
The origins of the Internet can be found in the early sixties, when the
US Department of Defense sponsored a project to develop a
telecommunications network that would survive a nuclear attack. It had to
link together a diverse set of computers and work in a decentralized
manner so that, if any part of the network were not functioning, network
traffic would automatically be re-routed via other network nodes. This
project quickly grew into a popular academic network linking virtually all
major research institutions and US universities. Thus linking academics and
researchers across the globe, it quickly became a means for global
information sharing.
The Internet consists of a huge and fast-growing number (hundreds
of thousands) of interconnected networks linked together.
The Web
The Internet service that has received the most attention from the
public media is the World-Wide Web or the Web for short (sometimes also
called WWW or W3). The Web is a collection of multimedia information
located on Web servers attached to the Internet.