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Network A system of interconnected computers and computerized peripherals such as printers is called computer network. This interconnection among computers facilitates information sharing among them. Computers may connect to each other by either wired or wireless media. A computer network consists of a collection of computers, printers and other equipment that is connected together so that they can communicate with each other.  

Network application
A Network application is any application running on one host and provides a communication to another application running on a different host, the application may use an existing application layer protocols such as: HTTP(e.g. the Browser and web server), SMTP(e.g. the email-client). And may be the application does not use any existing protocols and depends on the socket programming to communicate to another application. So the web application is a type of the network applications. 
There are lots of advantages from build up a network, but the th…


A computer is a device that accepts information (in the form of digitized data) and manipulates it for some result based on a program or sequence of instructions on how the data is to be processed. The term computer is derived from the Latin term ‘computare’, this means to calculate or programmable machine. Computer cannot do anything without a Program. It represents the decimal numbers through a string of binary digits. The Word 'Computer' usually refers to the Center Processor Unit plus Internal memory. 

Charles Babbage is called the "Grand Father" of the computer. The First mechanical computer designed by Charles Babbage was called Analytical Engine. It uses read-only memory in the form of punch cards. 

Computer is an advanced electronic device that takes raw data as input from the user and processes these data under the control of set of instructions (called program) and gives the result (output) and saves output for the future use. It can process both numerical and non-numerical (arithmetic and logical) calculations. 

Digital Computer Definition The basic components of a modern digital computer are: Input Device, Output Device, Central Processor Unit (CPU), mass storage device and memory. A Typical modern computer uses LSI Chips. 

Four Functions about computer are 

accepts data                            Input 
processes data                         Processing 
produces output                      Output 
stores results                           Storage 

Input (Data)

Input is the raw information entered into a computer from the input devices. It is the collection of letters, numbers, images etc. 


Process is the operation of data as per given instruction. It is totally internal process of the computer system. 


Output is the processed data given by computer after data processing. Output is also called as Result. We can save these results in the storage devices for the future use. 

Evaluation history

Generation in computer terminology is a change in technology a computer is/was being used. Initially, the generation term was used to distinguish between varying hardware technologies. But nowadays, generation includes both hardware and software, which together make up an entire computer system. The Types of computer 
Computers are divided into three types according to their structure, speed and architecture.

Analog Computers Digital Computers Hybrid Computers

    Analog Computers
  • Analog Computers

“The computers which provide us continuous information are called analog computers.” Analog computers represent physical quantities in the form of waves or in continuous form.


Thermometer is the example of analog computers because it measures the length of a mercury column continuously. A traditional clock is the example of analog computers because the needle of clock covers the distance of dial continuously. Weight machine and Speedo meter are other examples of analog computers. 

Characteristics of the analog computers

These computers have no state 
The Speed of analog computer is fast 
These computers are not reliable
These computers became the base for digital computers 
These computers are difficult to operate and use 
These computers are easy to develop These computers have small memory 
  • Digital Computers
Digital Computers
“The computers which present physical quantities with the help of symbols or numbers and provide us discrete information are called digital computers.” 


Digital watch, digital petrol stations and the computer, which we use nowadays, are the examples of digital computers

Characteristics of the digital computers

 Digital computers have two states On (0) and Off (1).  
 These computers are easy to use. 
 Human being like to use digital computers. 
These computers are reliable. 
Digital computers have big memory. 
Working speed of digital computers is slower as compared to analog computers. 
These computers are further divided into different categories such as personal computers, Mainframe computers and super computers.

  • Hybrid Computers
Hybrid Computers “The computers which have qualities of both digital and analog computers are called hybrid computers.

”Hybrid computer has the speed of analog and the accuracy of digital computer. Example: In ICU (Intensive care unit) of a hospital hybrid computers are used. These computers analog quality controls the temperature of the room digital quality informs the doctor about the blood pressure, temperature and physical status of the patient. In Cement factory a hybrid computer is used where all calculations are performed by the digital computers; and actions like increase of material are performed by the analog computers. 

Characteristics of the Hybrid computers

These computers are reliable and provide accurate result. 
These computers are fast and speedy. 

Generation & Description

a) First Generation

First GenerationThe period of first generation was 1946-1959. The computers of first generation used vacuum tubes as the basic components for memory and circuitry for CPU (Central Processing Unit). These tubes, like electric bulbs, produced a lot of heat and were prone to frequent fusing of the installations, therefore, were very expensive and could be afforded only by very large organizations. In this generation mainly batch processing operating system were used. Punched cards, paper tape, and magnetic tape were used as input and output devices. The computers in this generation used machine code as programming language. 

The main features of first generation are

  • Vacuum tube technology 
  • Unreliable
  • Supported machine language only
  • Very costly 
  • Generated lot of heat 
  • Slow input and output devices 
  • Huge size 
  • Need of A.C.
  • Non-portable
  • Consumed lot of electricity
Some computers of this generation were: 
  •  ENIAC 
  •  EDVAC 
  •  IBM-701
  •  IBM-650 

b) Second Generation

The period of second generation was 1959-1965. In this generation transistors were used that were cheaper, consumed less power, more compact in size, more reliable and faster than the first generation machines made of vacuum tubes. In this generation, magnetic cores were used as primary memory and magnetic tape and magnetic disks as secondary storage devices. In this generation assembly language and high-level programming languages like FORTRAN, COBOL were used. The computers used batch processing and multi-programming operating system. 

The main features of second generation are
  • Use of transistors
  • Reliable in comparison to first generation computers 
  • Smaller size as compared to first generation computers 
  • Generated less heat as compared to first generation computers
  •  Consumed less electricity as compared to first generation   computers 
  •  Faster than first generation computers
  •  Still very costly
  •  A.C. needed 
  •  Supported machine and assembly languages

Some computers of this generation were

  • IBM 1620 
  • IBM 7094
  • CDC 1604 
  • CDC 3600
  • UNIVAC 1108 

c) Third Generation

Third Generation

The period of third generation was 1965-1971. The computers of third generation used integrated circuits (IC's) in place of transistors. A single IC has many transistors, resistors and capacitors along with the associated circuitry. The IC was invented by Jack Kilby. This development made computers smaller in size, reliable and efficient. In this generation remote processing, time-sharing, multi-programming operating system were used. High-level languages (FORTRAN-II TO IV, COBOL, PASCAL PL/1, BASIC, ALGOL-68 etc.) were used during this generation. 

The main features of third generation are

  • IC used 
  • More reliable in comparison to previous two generations 
  • Smaller size 
  • Generated less heat 
  • Faster 
  • Lesser maintenance 
  • Still costly
  • A.C needed 
  • Consumed lesser electricity 
  • Supported high-level language
  • Some computers of this generation were 
  • IBM-360 series 
  • Honeywell-6000 series
  • PDP(Personal Data Processor) 
  • IBM-370/168 
  • TDC-316


The period of fourth generation was 1971-1980. The computers of fourth generation used Very Large Scale Integrated (VLSI) circuits. VLSI circuits having about 5000 transistors and other circuit elements and their associated circuits on a single chip made it possible to have microcomputers of fourth generation. Fourth generation computers became more powerful, compact, reliable, and affordable. As a result, it gave rise to personal computer (PC) revolution. In this generation time sharing, real time, networks, distributed operating system were used. All the high-level languages like C, C++, DBASE etc., were used in this generation. 

The main features of fourth generation are
  • VLSI technology used 
  • Very cheap 
  • Portable and reliable 
  • Use of PC's 
  • Very small size 
  • Pipeline processing 
  • No A.C. needed
  • Concept of internet was introduced 
  • Great developments in the fields of networks
  • Computers became easily available 
Some computers of this generation were
  • DEC 10
  • STAR 1000
  • PDP 11
  • CRAY-1(Super Computer) 
  • CRAY-X-MP(Super Computer)

e) Fifth Generation

The period of fifth generation is 1980-till date. In the fifth generation, the VLSI technology became ULSI (Ultra Large Scale Integration) technology, resulting in the production of microprocessor chips having ten million electronic components. This generation is based on parallel processing hardware and AI (Artificial Intelligence) software. AI is an emerging branch in computer science, which interprets means and method of making computers think like human beings. All the high-level languages like C and C++, Java, .Net etc., are used in this generation.

       AI includes

  • Robotics
  • Neural Networks
  • Game Playing 
  • Development of expert systems to make decisions in real life situations. 
  • Natural language understanding and generation. 
The main features of fifth generation are
  • ULSI technology 
  • Development of true artificial intelligence
  • Development of Natural language processing
  • Advancement in Parallel Processing 
  • Advancement in Superconductor technology 
  • More user friendly interfaces with multimedia features
  • Availability of very powerful and compact computers at cheaper rates 
Quick lookup of Computer Generation

Computer Generation (Period)
Keyword hardware Technology
Keyword Software Technology
Key Characteristic
Some Representative System


      ·       Vacuum Tube
      ·       Electro Magnetic Relay              Memory
      ·       Punched card Secondary            Storage memory
      ·       Machine and Assembly              Label language
      ·       Stored program Concept
      ·       Mostly Scientific calculation
      ·       Bulky in size
      ·       Highly Unreliable
      ·       Limited commercial Use        and costly
      ·       Difficult commercial              production
      ·       Difficult to use
     ·       ENIAC
     ·       EDVAC
     ·       EDSAC
     ·       UNIVAC 1
     ·       IMB 701

      ·       Transistor
      ·       Magnetic Core Memory
      ·       Magnetic tapes
      ·       Disks of Secondary                    Storage  
      ·       Batch Operating system
      ·       High level programming            language
      ·       Scientific and commercial           application
      ·       Faster, smaller, more              reliable and easier to              program than the                    previous generation of            computer
      ·       Commercial production          was still difficult and              costly
     ·       Honeywell 400
     ·       IBM 7030
     ·       CDC 1604
     ·       UNIVAC LARC

      ·       ICs with SSI and MSI                  technology
      ·       Large Magnetic core                    Memory
      ·       Larger capacity disks and            Magnetic tapes
      ·       Time sharing operation                system
      ·       Standardization of high               level   programming                   language
      ·       Unbounding of software             form hardware
     ·       Faster, smaller more               reliable and easier and           cheaper to produce
     ·       Commercially easier to           use
     ·       IBM 360/370
     ·       PDP-8
     ·       PDP-11
     ·       CDC 6600

      ·       ICs with VLSI technology
      ·       Microprocessor,                            semiconductor memory
      ·       Large capacity of hard disk          drive
      ·       Magnetic tapes and floppy          disk as portable storage                media
      ·       Spread of high speed                    computer network
      ·       OS for the PCs with GUI            and multiple window in the        single terminal screen.
      ·       Multiprocessing OS with            concurrent programming            language
      ·       UNIX OS with C                        programming language
      ·       Object oriented designing          and programming
     ·       Small ,affordable, reliable and easy to use PCs
     ·       More powerful and         powerful mainframe systems and super computer
     ·       Totally general purpose          machine
     ·       Easier to upgrade
     ·       Rapid software development is possible
·       IBM PC
·       Apple 2
·       TRS-80
·       CRAY-1
·       CRAY-2
·       CRAY-X/MP


    ·       ICs with ULSI technology
      ·       Larger capacity of main              memory, hard disk
      ·       Power server and super                computer
      ·       Internet
      ·       Multimedia ,Internet                  application
      ·       Java
      ·       World wide we
      ·       More complex                            super computing application
·       Portable computer
·       Powerful cheaper, reliable and easier to use desktop machine
·       Rapid software development is possible
·       Easier to produce commercially and easier to upgrade.
·       SUN
·       IBM Notebook
·       IBM SP/2
·       SGI Origin 2000
·       PARAM 10000

 Some computer types of this generation are

  • Desktop
  • Laptop 
  • Note Book
  • Ultra-book 
  • Chrome-book

Computer Classification: By Size and Power

Sl no

(Personal Computer)
It is a single user computer system having moderately powerful microprocessor

It is also a single user computer system which is similar to personal computer but have more powerful microprocessor.

Mini Computer
It is a multi-user computer system which is capable of supporting hundreds of users simultaneously.

Main Frame
It is a multi-user computer system which is capable of supporting hundreds of users simultaneously. Software technology is different from minicomputer.

It is an extremely fast computer which can execute hundreds of millions of instructions per second.

PC (Personal Computer)

 A PC can be defined as a small, relatively inexpensive computer designed 
for an individual user. PCs are based on the microprocessor technology that enables manufacturers to put an entire CPU on one chip. Businesses use personal computers for word processing, accounting, desktop publishing, and for running spreadsheet and database management applications. At home, the most popular use for personal computers is playing games and surfing Internet. Although personal computers are designed as single-user systems, these systems are normally linked together to form a network. In terms of power, now-a-days High-end models of the Macintosh and PC offer the same computing power and graphics capability as low-end workstations by Sun Micro-systems, Hewlett-Packard, and Dell. 


Workstation is a computer used for engineering applications (CAD/CAM), desktop publishing, software development, and other such types of applications which require a moderate amount of computing power and relatively high quality graphics capabilities. Workstations generally come with a large, high-resolution graphics screen, large amount of RAM, inbuilt network support, and a graphical user interface. Most workstations also have a mass storage device such as a disk drive, but a special type of workstation, called a disk-less workstation, comes without a disk drive. Common operating systems for workstations are UNIX and Windows NT. Like PC, Workstations are also single-user computers like PC but are typically linked together to form a local-area network, although they can also be used as stand-alone systems. 


 It is a midsize multi-processing system capable of supporting up to 250 users simultaneously.


Mainframe is very large in size and is an expensive computer capable of supporting hundreds or even thousands of users simultaneously. Mainframe executes many programs concurrently and supports many simultaneous executions of programs 


 Supercomputers are one of the fastest computers currently available. Supercomputers are very expensive and are employed for specialized applications that require immense amount of mathematical calculations (number crunching). For example, weather forecasting, scientific simulations, (animated) graphics, fluid dynamic calculations, nuclear energy research, electronic design, and analysis of geological data (e.g. in petrochemical prospecting).

 Essential Computer Unit 

All types of computers follow a same basic logical structure and perform the following five basic operations for converting raw input data into information useful to their users. 


Take Input
The process of entering data and instructions into the computer system

Store Data
Saving data and instructions so that they are available for processing as and when required.

Processing Data
Performing arithmetic, and logical operations on data in order to convert them into useful information.
Output Information
The process of producing useful information or results for the user, such as a printed report or visual display.
Control the workflow
Directs the manner and sequence in which all of the above operations are performed.

Input Unit 

This unit contains devices with the help of which we enter data into computer. This unit makes link between user and computer. The input devices translate the information into the form understandable by computer.

CPU (Central Processing Unit) 

CPU is considered as the brain of the computer. CPU performs all types of data processing operations. It stores data, intermediate results and instructions (program). It controls the operation of all parts of computer.

CPU itself has following three components

  • Memory Unit  
  • Control Unit 
  • ALU(Arithmetic Logic Unit) 

Output Unit

Output unit consists of devices with the help of which we get the information from computer. This unit is a link between computer and users. Output devices translate the computer's output into the form understandable by users. 

Memory or Storage Unit

This unit can store instructions, data and intermediate results. This unit supplies information to the other units of the computer when needed. It is also known as internal storage unit or main memory or primary storage or Random access memory (RAM). 
Its size affects speed, power and capability. Primary memory and secondary memory are two types of memories in the computer.

 Functions of memory unit are: 

➤ It stores all the data and the instructions required for processing. 
➤ It stores intermediate results of processing. 
➤ It stores final results of processing before these results are released to an output device. 
➤ All inputs and outputs are transmitted through main memory. 

Control Unit

This unit controls the operations of all parts of computer but does not carry out any actual data processing operations.
Functions of this unit are:
➤It is responsible for controlling the transfer of data and instructions among other units of a computer.
➤It manages and coordinates all the units of the computer. 
➤It obtains the instructions from the memory, interprets them, and directs the operation of the computer. 
➤It communicates with Input/output devices for transfer of data or results from storage. 
 It does not process or store data. 

ALU (Arithmetic Logic Unit)

  • This unit consists of two subsections namely
  • Arithmetic section 
  • Logic Section
Arithmetic Section

Function of arithmetic section is to perform arithmetic operations like addition, subtraction, multiplication and division. All complex operations are done by making repetitive use of above operations.

Logic Section

Function of logic section is to perform logic operations such as comparing, selecting, matching and merging of data. 

User Interface

An interface is a set of commands or menus through which a user communicates with a program. A command-driven interface is one in which you enter commands. A menu-driven interface is one in which you select command choices from various menus displayed on the screen. The user interface is one of the most important parts of any program because it determines how easily you can make the program do what you want. A powerful program with a poorly designed user interface has little value. Graphical user interfaces (GUIs) that use windows, icons, and pop-up menus have become standard on personal computers. CUI and GUI are acronyms that stand for different kinds of user interface systems. These are terms used in reference to computers. CUI stands for Character User Interface while GUI refers to Graphical User Interface. Though both are interfaces and serve the purpose of running the programs, they differ in their features and the control they provide to the user. Here is a brief explanation of the two types of user interface for the help of those who do not know about them. 
  • CUI CUI means you have to take help of a keyboard to type commands to interact with the computer. You can only type text to give commands to the computer as in MS DOS or command prompt. There are no images or graphics on the screen and it is a primitive type of interface. In the beginning, computers had to be operated through this interface and users who have seen it say that they had to contend with a black screen with white text only. In those days, there was no need of a mouse as CUI did not support the use of pointer devices. CUI’s have gradually become outdated with the more advanced GUI taking their place. However, even the most modern computers have a modified version of CUI called CLI (Command Line Interface).
  • GUI: GUI is what most modern computers make use of. This is an interface that makes use of graphics, images and other visual clues such as icons. This interface made it possible for a mouse to be used with a computer and interaction really became very easy as the user could interact with just a click of the mouse rather than having to type every time to give commands to the computer. 
  • Hardware Computer hardware is the collection of physical parts of a computer system. This includes the computer case, monitor, keyboard, and mouse. It also includes all the parts inside the computer case, such as the hard disk drive, motherboard, video card, and many others. Computer hardware is what you can physically touch. 
  • Software Software is a generic term for organized collections of computer data and instructions, often broken into two major categories: system software that provides the basic non-task-specific functions of the computer, and application software which is used by users to accomplish specific tasks. Software is basically two types i) System software ii) Application Software. Let’s discuss about the both subcategories of the software. 

 I. System Software

System software is responsible for controlling, integrating, and managing the individual hardware components of a computer system so that other software and the users of the system see it as a functional unit without having to be concerned with the low-level details such as transferring data from memory to disk, or rendering text onto a display. Generally, system software consists of an operating system and some fundamental utilities such as disk for-matters, file managers, display managers, text editors, user authentication (login) and management tools, and networking and device control software.

 II.  Application Software

Application software, on the other hand, is used to accomplish specific tasks other than just running the computer system. Application software may consist of a single program, such as an image viewer; a small collection of programs (often called a software package) that work closely together to accomplish a task, such as a spreadsheet or text processing system; a larger collection (often called a software suite) of related but independent programs and packages that have a common user interface or shared data format, such as Microsoft Office, which consists of closely integrated word processor, spreadsheet, database, etc.; or a software system, such as a database management system, which is a collection of fundamental programs that may provide some service to a variety of other independent applications. 


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