What is Computer

Computer Appreciation (what is computer)

Introduction For Computer :- 

The computer is one of the major component of information Technology Information technology and the computer; influence every aspect of human life today, whether it is in business or satellite launching, In this block, we will introduce you to the computer, its parts and how it work. A computer is basically a programmable computing machine. Earlier computers were used for complex computations and used by only scientists and engineers. They were costly and hence only large organizations could afford them. These computers being very fast in calculating can be used not only for computation but also to store and retrieve information. They control chemical processes and machines. They can in 1822 an English man Charles Babbage has made an important effort in the Manufacturing of modem computer. He is called the father of the computer.

The word Computer comes from the Greek word computer which means to calculate so a computer is normally considered to be a calculating device that can perform arithmetic operations at enormous speed.


Characteristics of Computer :-

(1).  Speed

(2).  Accuracy

(3).  Diligence

(4).  Storage

Speed :-  A computer is very fast device. It can perform large amount of work in a few seconds that human being can do in an entire year.

Accuracy :-  A compute produce very accurate result. A human can make the mistake but computer never. It performs both arithmetical calculation and logical operations with accuracy. Errors can occur in a computer due to the fault (mistake) of human beings. Errors may occur due to imprecise thinking by that programmer or incorrect input data.

Diligence :-  Unlike human beings a computer is free from tiredness and monotony. It can continuously work for hours without creating my error.

Storage :-  A computer can store and recall any amount of information because of it secondary storage capability. With the help of the storage devices you store the data for the future use. Every piece of information can be retained as long as desired by the user and can be recalled, when required.

Disadvantage of Computer :-  Incapable to take any decision by it self it cannot judge by itself for any valid or invalid data. Required regular maintains.

The computer Generation :-  Generation in computer talk is a step in technology; it provides a framework for the growth of the computer industry. There are totally five computer generations known until today. Each generation has been discussed below in detail along with its identifying characteristics.

First Generation 1(1942 – 1955)

Some of the early computers – ENIAC, EDVAC, EDSAC, UNIVACI, AND IBM 701. Were built by using thousands of VACUUM TUBES A vacuum tube was a fragile glass device, which used filaments as a source of electronics, and could control and amplify electronic signals. These vacuum tube computers could perform computations in milliseconds, and were referred to as first – generation computers.

The characteristic features of first – generation computers are as follows :-

1.  They were the fastest calculating devices of their time.

2.  They were too bulky in size, requiring large rooms for installation.

3.  Thousands of vacuum tubes, which were uses, emitted large amount of hear and burnt out frequently.

4.  Heavy weight and high cost.

Second Generation (1955 – 1964)

The second generation computers were manufactured using transistors, instead of vacuum tubes. Due to the properties of transistors, the second generation computers were more powerful more reliable, less expensive, smaller, and cooler to operator than the first generation computers. The first generation computers were mainly used for scientific computations.

However, in the second generation, an increasing usage of computers was seen in business and industry for commercial data processing applications like payroll, inventory control, marketing, and production planning.

The characteristics features of second- generation computers are as follow :-

1.  They were more than ten times faster than the first – generation computers.

2.  They were much smaller than firsts-generation computers, requiring smaller space.

3.  They were portable.

4.  They consumed much less power than the first-generation computers.

Third Generation (1964 – 1975)

In 1964 the integrated Circuits (IC) replaced the transistors. Integrated circuits are circuits consisting of several electronic components like transistors , resistors, and capacitors grown on a single chip of silicon, eliminating wired interconnection components. ICs were much smaller, less expensive to produce, more rugged and reliable faster in operation, dissipated less heat and consumed much less power than circuits built by wiring electronic components, manually. Hence third-generation computers were more powerful, more reliable, less expensive, smaller, smaller, and cooler to operate then the second – generation computer.

The characteristic feature of third – generation computers are as follows:

1.  They were much more powerful then the second generation computers.

2.  They were much smaller than second generation computers, requiring smaller space.

3.  They was a further cost reduction.

4.  They consumed much less power than the second generation computers.

Fourth Generation (1975 – 1989)

The forth generation computer appeared in 1970’s utilizing still newer electronic technology. The fourth generation computer were built a number of silicon chips were used in a discrete circuit hence a single Microprocessor chip was useful to accommodate the entire functional circuit. One of the major inventions, which led to the forth generation was the LSI (Large Scale Integrated).

They characteristic features of fourth – Generation computers are as follow:

1.  Easily portable.

2.  Further reduction in size and weight.

3.  They consumed much less power than the third – generation computers.

4.  Graphical user interface (GUI) enable new user to quickly learn how to use computers.

Fifth Generation (Present and Beyond) :-

Fifth generations computers are only in the minds of advance research Scientists and being tested out in the laboratories. This computer will be under Artificial intelligence (AL), they will be able to take commands in as audio visual way and carry out instruction. Many of the operations which require low human intelligence will be performed by these computers.

The Hardware – component of the Computer

The physical components of a computer are known as hardware, Such physical components may be electronic, magnetic, mechanical or optical. Hardware is any art of the computer you can touch. Hardware consists of interconnected electronic device that you can use to control the computer’s operation, input, and output. The generic term device refers to any piece of hardware.








Input device :-  Input device are used tso give instructions to the computer. Data and instructions are entered into a computer through input device. An input device first converts desired inputs data and instructions into a suitable binary form and then feed its into the CPU. The commonly used input device is the keyboard and mouse.

Keyboard :-  Keyboard is an input device, which allows the user to enter data or command into computer system, A keyboard is similar to the keyboard of a typewriter. It contains alphabets, digits, special, characters, function keys and some control keys.

Difference Dtypes of keys and their functions are described in the following sections.

Alphanumeric Key :-  All of the letters and Numbers on the Keyboard, A – Z and 0-9.

Punctuation Keys :-  All of the keys associated with punctuation such as the comma, period, semicolon, brackets, and parenthesis and so on. Also all of the mathematical operators such as the + sign, – sign, and = sign.

Special Keys :-  All of the other keys on the computer keyboard such as the function keys, control keys, arrow keys, caps lock key, delete key, etc.

Special keys on a PC keyboard :

Alt key – Short for Alternate, this key is like a second control key.

Arrow keys – Most keyboards have four arrow keys that enable you to move the cursor up, down, right, or left. Used in conjunction with the shift or Alt keys, the arrow keys can move the cursor more than one position at a time, but this depends on which program is running.

Backspace key – Deletes the character just to the left of the cursor 9or insertion point) and moves the cursor to that position.

Caps Lock Key – A toggle key that, when activated, causes all alphabetic characters to be uppercase.

Ctrl Key – Short for control, this key is used in conjunction with other keys to produce control characters. The meaning of each control character depends on which program is running.

Delete Key – Sometimes labeled Del, deletes the character at the current cursors position, or the selected object, but does not move the cursor. For graphics – based applications, the Delete key deleted the character to the right of the insertion points.

Enter Key – Used to enter commands or to move the cursors to the beginning of the next line. Sometime labeled return instead of Enter.1

Esc Key – Short for Escape, this key is used to send special codes to devices and to exit or escape from programs and tasks.

Function Keys – Special keys labeled F1 to F12 These keys have different meaning depending on which program is running.

Joystick :-  A joystick is multidirectional device used to play the games. A joystick is also a pointing device. It is used to move the cursor position on a monitor screen, its function is similar to that of a mouse and is used for playing games.

Scanner :-  Scanner is an input device used to store image digitally as well as text into the computer. The main advantage of direct entry of information is that users do not have to type information this provides accurate data entry.

Mouse :-  Mouse is an input device, which is use to select the option in the window. It is a small device that is connected to the system unit by means of a long wire. The mouse can also be used to draw sketches, diagrams etc. on the monitor screen. It is also moved on the graphics tablet for drawing work. The mouse is also used to edit text.

OMR (Optical Mark Reader) :-  Optical Mark Reader is special scanner used for recognizing a pre –  specified type of mark made by pencil or pen. For example in the objective test paper of DOEACC, you mark your answers on a special sheet by darkening a small square, using a pen or pencil. These answer sheets are fed into the computer using the optical mark reader. The computer can then evaluate the answer sheets. The optical mark reader. The computer can then test. In fact any input data that is in the nature of a choice or section can be recorded for OMR input.

Bar Code Reader :-  Bar code readers are special devices used to read bar coded data. Bar code is a specialized code used for fast identification of items. It consists of a series of small lines, known as bars. The actual coding of goods such as books, postal packages, badges.

MICR (Magnetic Ink Character Recognition):-  MICR detects the special encoded character on bank cheque and deposit slips. After detecting the encoded characters, the MICR converts them into digital data for the computer.

OCR (Optical Character Reader):- This device is capable of detecting alphabetic and numeric character on a computer print out containing compete pages of typed text or hand written text. The characters are examined by passing them under a strong light and a lens system. The linked areas are differentiated from those which are not inked. Once the whole character is scanned it is compared with the character matches, the scanner character is accepted for future operations.

Output devices :-  Output device are used to show the information store in a computer or the result of any processing done by the computer to the outside world. There are many output devices Manufactured for this purpose, but the most commonly used devices are the video, monitor, and printer. Printer provides a permanent record on a paper.

VDU :-  VDU stands for visual display unit. Also known as monitor. A VDU or a monitor is very similar to a television and its size (as in the case of TV) is measured in diagonal length of the screen. Monitors are available in 9” , 12”,14”, 15”, 17”, and 19” and even in 21” size. It shows text or picture in color or black and white, depending on the type. Color monitor are more costly than black and white monitors. Whatever you type on the keyboard, you can See it on the monitor.

Printer :-  Printers are the most popular output devices. They provide information in a permanent readable form. They produce printed outputs of results, programs and data. A character printer prints one character of the text at a time. The printers commonly used with the PC are the Dot – matrix printer, Ink jet printer, and Laser printer.

Dot Matrix Printer :- 

A). Prints character in form of dots

B). Cheap in cost

C). Black & white

D). Slow print speed

E). Produce noise while printing

Ink jet Printer :- 

A). Prints fully from characters

B). Moderate expensive

C). Color

D). Moderate print speed

E). Less noise

Laser Printer :- 

Prints fully from character

Very expensive


Fast print speed

No noise

Plotter :-  Is an output device used to draw high – resolution charts, graphs, layouts and other live based diagram and often used with CAD (Computer – Aided – Design). They are used to produce precise and good quality graphics and drawings under control of the computer. They use ink pen or inkjet to draw graphics or drawings. Wither single color or multicolored pens can be employed. 

CPU :-   CPU  stands for Central Processing unit. It is the brain of the computer. In a human body, all major decisions are taken by the brain and all other parts of the body function as directed by the brain. Similarly, in a computer system, all major calculations, manipulations and comparisons are made by the CPU. The CPU is also responsible for activating and controlling the operations performed by all other units of the computer system.

The major parts of a CPU are:

A). Arithmetic and Logic unit (ALU)

B). Control unit (CU)

C). Main Memory or Primary Memory.

How does a Computer works OR woking Cycle?

Computer follows the basic principle of input – process – output. Each component of the PC system is related to the I – P+ – O cycle. The computer takes the input via the input device such as keyboard.


The processing is done by a component of the system unit c allied Microprocessor and output displayed on the VDU.

Storage Device :-

The data is stored in storage device for processing and for future use. These are two types of storage devices.

A). Primary Storage

B). Secondary storage.

Primary Storage Device :- 

Primary Memory is also known as main memory. Main memory is also called RAM (random access memory). Primary memory is two tyipes.



RAM :-  The most cfommon type of memoryi is called random access memory, or ram. Ram is a read/write memory. Can be written into and read from a RAM. It is a volatile memory. It retains the stored information as long as it is supplied with power supply. When power supply is switched off or interrupted, the stored information in the RAM of lost. TAM of various capacities is available, for example, 256MB and so on. There are two important types of RAM Static RAM and Dynamic RAM. Static RAM can retain stored information as long as the power supply is on. But a Dynamic RAM loses its stored information in a very short time (a few milliseconds) even though the power supply is on.

ROM :-  Itd is called Read Only Memory. ROM is Non – Volatile chips always hold the same data. It is permanent type memory. Its contents are not lost when power supply is switched off. The user cannot write into a ROM. Its contents are written into at manufacturing time. ROM store permanent program and other types of data which are needed by the computer to execute user programs.

Secondary Storage Device :-  You cannot store data in the main memory of a PC permanently. Firstly because it is very expensive and secondly its contents are erased when the computer is turned off. That is, main memory stores data and instructions only temporarily. In order to preserve or save the work which you have done on your computer (permanently for future use) before you shut it off, you have to use storage media such as floppy disks, compact disks (CDs) and hard disk.

Hard Disk

Floppy Disk

Hard Disk :- Hard disks are fast and have more capacity than floppy disks and permanently placed in side the computer. It is v ery expensive compare to floppy disk. Hard disk can store large amount of date typically 20GB, 40GB, 80GB, 160GB, capacities of hard disk are available.

Floppy Disk :- Floppy disk is a portable secondary storage device which is use to copy the date from one machine to another. A floppy disk, also called a disk or diskette, is a removable storage disk used for storing data. It is called a floppy disk because the round film inside the disk’s plastic shell is flexible (floppy). You should make a copy of any important information from the hard disk in a flopp. This is known as keeping a backup of important information.

Types of Floppies : –  Floppies are available in the following two sizes with varying storage capacities :-

5.25” floppy disk capacity :- 1.25 MB


Hard DiskFloppy Disk
Always represents by C: or D:Always represents by A: or B:
Non removableRemoval
Large storage capacity (80MB to 20MBBand more)Less storage capacity (1.44 MB)

Measurement of Memory:

In computer technology, the storage capacity is measured in terms of bytes. Where

A). 1 character = 1 bytes

B). 1 byte = 8 bits (Bits are the binary digits that is 0 or 1)

C). 1 KB = 1024 bytes where KB Stand for Mega byte

D). 1 MB = 1024 KB where MB stand for Mega byte

E). 1 GB = 1024 MB where GB stand for Giga byte

F). 1 TB = 1024 GB where TB stand for Tera byte.

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