Computer Fundamental Complete Course for Computer Operator

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लोकसेवा आयोग, नेपाल विविध सेवा, राजपत्र अनंकित प्रथम श्रेणी तथा स्थानीय सेवा अन्तर्गत प्राविधिकतर्फ विविध सेवा, चाैथो र पाँचाैं तहका कम्प्यूटर अपरेटर पदहरुका लागि महत्वपूर्ण पाठ्यक्रम।

 लोकसेवा आयोग, नेपाल प्रहरी, नेपाल विद्युत प्राधिकरण, नेपाल टेलिकम, महानगरपालिका, नेपाल आयल निगम, कर्मचारी सञ्चयकोष, त्रिवि सेवा आयोग,  Information and Communication Technology (ICT) सँग सम्बन्धित विद्यार्थीहरुका लागि समेत अत्यन्त उपयोगी।

Computer Fundamental is one of the most important chapter for the Preparation of Computer Operator and Assistant Computer Operator exams.

Computer-Fundamental Info-graphics
Computer-Fundamental Info-graphics
Computer Fundamental

INTRODUCTION TO COMPUTER

A computer is an electronic machine that can perform several tasks according to the given instructions. A computer takes data and instructions as input. It processes the data according to the instructions and produces meaningful information as an output. A computer can also store the data and information for future use.

Computer System

The word “Computer” is derived from the Latin word “COMPUTARE” which means to calculate or compute. In the past, the computer was normally considered as a calculating device used to perform different calculations. But today’s modern computer is able to perform several tasks. So, the computer can be defined as:

A computer is an electronic machine that takes data and instructions as an input, processes the data according to the given set of instructions and gives the meaningful information as result.

Or

Computer is an electronic machine which generates information by processing raw data according to the prescribed sequence of instructions.

A computer has four basic parts. They are: keyboard, mouse, monitor and system unit (CPU tower).

Features of a Computer

Today computer has become a part of general lives, because of its greater impact on society. Due to its special features computer is widely accepted machine world-wide. The following are the common features of computer:

  • Speed

A computer can work very fast. The processing speed of computer is close to the speed of light. One second is a very long time for computer. It can perform several tasks within a second. A computer has the capability to do several complex calculations within a second. The time taken by the computer to perform an operation is called the processing speed. The speed of computer is measured in terms of fractions of seconds which is listed below:

1 millisecond 1/1000 th second
1 microsecond  1/1000000 th second
1 nanosecond 1/1000000000 th second
1 picosecond 1/1000000000000 th second
  • Accuracy

A computer is believed as an accurate machine because the results obtained from the computer are error free. If the data and instructions given to the computer are correct, it will always produce accurate results or output. Sometimes it also may produce undesirable results which is due to wrong input. In computer terminology, it is known as garbage in garbage-out (GIGO).

  • Diligence

A computer can perform repetitive  job continuously and never gets tired or bored while working. It can regularly work for long a long time without losing its speed and accuracy. It also can do the same task again and again. Therefore, it is called a diligent machine.

  • Versatility

Computer is a versatile and flexible machine because it can do wide varieties of jobs depending upon the instructions fed to it. It can perform different kinds of tasks in the various fields such as calculations. drawing pictures, playing games, playing music, writing letters, sending emails, etc.

The working capacity of computer is dependent on the software. Due to this feature we can use the same computer in different fields of work such as education, business, communication, entertainment, desktop publishing, etc.

  • Storage

A computer can store huge amount of data in its internal or external memory. In primary memory it stores data and program for current purpose whereas in secondary memory it stores data and program for future purpose. The stored data and programs are available any time for processing. The following are the measurement units used to count the stored data in computer system.

0 or 1 1 bit
4 bit 1 nibble
8 bit 1 byte/ 2 nibble
1024 bytes 1 kilobyte
1024 kilobytes 1 Megabyte
1024 Megabytes 1 Gigabyte
1024 Gigabytes 1 Terabyte
  • Communications

Now- a- days computer is mostly used in the field of communication to exchange messages or data through Internet all over the world. With the help of a computer, you can quickly receive or send information throughout the world. There are many services available on computer through which communications are possible such as email, chatting, video conferencing, net-phone, skype, etc.

Limitations of Computer

The main limitations of computers are as follows :

  1. Computer has no intelligence of its own.
  2. Computer fully depends upon human beings.
  3. Computers have no feelings and no emotion because they are machine.
  4. Computer cannot learn from the past experience.
  5. Computer cannot change the execution steps itself.
  6. Computer needs power backup (electricity) to work.

Application Fields of Computer

Computer is one of the most useful electronic machines for our daily life. After the invention of the personal computer it has revolutionised the world and could be used in every field. Today we cannot imagine the field where computer is not used. The major and common application fields of computers are as follows.

Uses of Computer

Important Points to Remember

  1. Computer is an electronic machine that can perform several tasks according to the given instructions.
  2. The word “Computer” is derived from the word “computare” which means to calculate.
  3. A computer has four main parts: keyboard, mouse, monitor and system unit.
  4. Some features of a computer are: Speed, Accuracy, Diligence, Versatility, Storage, Communications etc.
  5. Today computers are used in almost all the fields such as homes, education, entertainment, business, health care, agriculture etc.

History of the Computer

Modern computers are developed after a gradual change over a long period of time. In ancient times, human beings started counting using own fingers. However, the limited numbers of fingers had made it difficult for them to remember more facts. Thus, they started different methods to count using stones, sticks, scratches on a rock or wall or a knot in a string. As a result, during the fifth century, Hindu philosophy developed a new method of counting using the numbers of 0 to 9. The history of computer implies the gradual change in the concept over a long period of time. In the following section, we explain about the history of computing machines from their early forms to the most modern high speed electronic computers.

Abacus

Abacus Computer Operator
Abacus

The history of computers can be traced back to 3000 B.C. The Stone Age human being used small round stones for counting cattle. Later, a device called Abacus was developed by the Chinese to perform simple calculations such as addition, subtraction, multiplication and division. This is regarded as the first mechanical computing device. It is a rectangular box, divided into two parts by mid bar, upper part is called heaven that consists of two beads and each bead equal to value 5 and lower part is called earth, consists of five beads and each bead is equal to value 1. Calculations are performed by manipulating the beads in an Abacus.

Napier’s Bones

Napiers bones Computer Operator
Napiers bones Computer Operator

In 1614 A.D., John Napier, a Scottish mathematician developed device, which was called Napier’s Bones. With the help of this device, multiplication and addition were possible. Multiplication tables were renowned on strips of wood or bone. It is possible to perform calculations with two numbers and mainly used for multiplication table.

Slide Rule

Slide Rule Computer Operator
Slide Rule

Slide rule was invented by William Oughtred in 1620A.D. He was an English mathematician. Slide Rule was the first analog device that used the principle of logarithms. It could perform simple multiplication and division problems. It consists of 2 sets of rulers joined together with a marginal space between them. The proper alignment of two rulers enables to perform multiplication and division by the method of addition and subtraction.

Pascaline

Pascaline Computer Operator
Pascaline

Pascaline was developed by Blaise Pascal in 1642 A.D. It contains eight dials, gears and toothed metal wheels. It was capable of performing additions and subtractions up to 8 digits. It could add and subtract by the movement of wheels and not used for division and multiplication. odometer works with the same principle of pascaline.

Stepped Reckoner 

Stepped Reckoner Computer Operator
Stepped Reckoner

It was developed by Gottfried Wilhelm Von Leibniz, a German Mathematician and philosopher in 1694A.D. The centerpiece of this machine was its stepped drum gear design also known as modified version of Pascaline. It was the first calculator to perform all four of the basic arithmetic functions, addition, subtraction, multiplication and division. It could also evaluate square roots by a series of stepped additions.

Jacquard’s Loom

Jacquard Loom Computer Operator
Jacquard Loom

A French inventor Joseph Marie Jacquard invented an automatic weaving machine called Loom in 1801 A.D. This loom used punched cards to produce certain pattern in the woven cloth. The function of loom depends on the absence or presence of holes on the punched cards. This concept of loom gave the idea of Binary Digits, 0 or 1 (Yes or No). This concept can be considered as an important contribution to the evolution of the modern computer.

Difference Engine and Analytical Engine 

Difference and Analytical Engine Computer Operator
Difference and Analytical Engine

In 1822 A.D, Charles Babbage, a professor of mathematics at Cambridge University, devised an automatic calculating machine called Differential Engine. This machine was used to perform simple computation needed for setting up trigonometric and logarithmic tables.

Atanasoff Berry Computer (ABC)

Professor of physics and mathematics, John Vincent Atanasoff and his assistant Clifford Berry in 1942 A.D, designed the first electronic and digital computer popularly known as Atanasoff Berry Computer (ABC). It has used vacuum tubes as the main memory.

ABC Computer Operator
ABC Computer

Electronic Numerical Integrator and Calculator (ENIAC)

ENIAC was the first general purpose electronic computer developed by John William Mauchly and John Presper Eckert in 1946 A.D. It contained 18000 vacuum tubes as the main memory and based on decimal numbers. It could perform many complex arithmetic operations within a second.

ENIAC Computer Operator Nepal
ENIAC Computer

Electronic Discrete Variable Automatic Computer (EDVAC)

John William Mauchly, John Presper Eckert in 1952 A.D, developed EDVAC. A Hungarian mathematician, John Von Newman in 1947 A.D, had already introduced this concept. It contained a magnetic tape as a memory device. It was based on binary number system and known as first stored program computer.

Electronic Delay Storage Automatic Computer (EDSAC)

EDSAC was the first operational stored program computer developed by Professor Maurice Wilkes and his team. It was started in 1947 A.D. and executed the first program in 1949 A.D. at the University of Cambridge, Mathematical Laboratory. It contained 6000 vacuum tubes and it required 30 kilowatts of electric power. In this, program was input using paper tape and output results were printed on a teletype page printer.

Universal Automatic Computer (UNIVAC-I)

UNIVAC-I was developed by John William Mauchly, John Presper Eckert in 1951 AD. It was the first general purpose electronic digital computer for commercial users. It could handle both numbers and letters. This computer consisted of magnetic tape for data input and output. This computer was used for data processing until 1963 A.D. in America. All the above discussed conspicuous contributions were considerably relevant in the development of today’s computers.

GENERATION OF COMPUTER

The modern computer which we use today is not the result of the first attempt made by the engineers and mathematicians. It has taken a big leap forward with each technological breakthrough during the development process. The computer’s functions and speed of their operation has been changing. Not only that, its size and cost also has been changing. Technological breakthrough in hardware and software brought more and more advanced computer system. It has been identified that there are five major stages in the continuous development process of the computer generation. Each generation is based on particular technological class.

First Generation of Computers

The first generation computers were developed during 1946 to 1958 A.D. The technology used in these computers was Vacuum Tube. This technology was first developed by Lee De Forest in 1908 A.D.First generation computers relied on machine language to perform operations, and they could only solve one problem at a time Input was based on punched cards and paper tape, and output was displayed on printouts. ENIAC, EDVAC, EDSAC, UNIVAC-I, IBM 650 are examples of the first generation computers.

First Generation of Computer
First Generation of Computer
  • Characteristics of the first generation Computers
    • These computers used vacuum tubes as the main electronic component.
    • These computers were very big in size.
    • These computers were slow in speed and had less storage capacity.
    • These computers occupied very large space.
    • These computers had low level of accuracy and reliability.
    • These computers used only machine language and could do only specific tasks.
    • These computers were mainly used in commercial and scientific applications.
    • The operating speed of these machines was measured in milliseconds.

Second Generation of Computers

The second generation computers were developed during 1959 to 1964 A.D. The technology used in these computers was Transistors. This technology was first developed by three scientists named, William Shockley, John Bardeen and Walter Brattain in 1947 A.D. Second-generation computers still relied on punched cards for input and printouts for output. Second-generation computers moved from cryptic binary machine language to symbolic, or assembly languages, which allowed programmers to specify instructions in words. IBM 1620, IBM 1401, Controlled Data Corporation 3600 are examples of second generation computers.

Second Generation of Computer
Second Generation of Computer
  • Features of Second generation Computers
    • These computers used transistors as the main electronic component.
    • These computers were much smaller and generates less heat than the first generation computers.
    • These computers had more storage capacity.
    • These computers consumed less electric power than the first generation computers.
    • These computers were faster, less expensive and more reliable than the first generation computers.
    • Assembly and high-level language could be used in the second generation computers.
    • These computers were more accurate than the first generation Computers.
    • The first computers of this generation were developed for the atomic energy industry.

Third Generation of Computers

The third generation computers were developed during 1965 to 1974 A.D. The technology used in these computers was Integrated Circuit Chip (IC Chip). This technology was first developed by Jack Kilby in 1958 A.D. The development of the integrated circuit was the hallmark of the third generation of computers. Instead of punched cards and printouts, users interacted with third generation computers through keyboards and monitors and interfaced with an operating system, which allowed the device to run many different applications at one time with a central program that monitored the memory. Computers for the first time became accessible to a mass audience because they were smaller and cheaper than their predecessors. IBM 360, ICL 900 Series, IBM 370 series are examples of third-generation computers.

Third Generation of Computer
Third Generation of Computer
  • Features of Third Generation Computer
    • These computers used IC chip as the main electronic component.
    • IC Chip are much smaller than transistors, draw less power, and generate less heat in these machines.
    • The size of computers became much smaller it was a vast improvement over the second generation computer.
    • The operating speed of these machines was measured in nanoseconds.
    • They used assembly and high-level language for programming.
    • These computers were more accurate and reliable than the second generation computers.
    • They had larger storage capacity.

Fourth Generation of Computers

The fourth generation computers (intel were developed during 1975 till present. The technology used in these computers was Microprocessor (LSIC = Large Scale Integration Circuit, VLSIC= Very Large Scale Integration Circuit). This technology was first developed by American Intel Corporation in 1971 A.D. The microprocessor brought the fourth generation of computers, as thousands of integrated circuits were built onto a single silicon chip. The Intel 4004 chip, developed in 1971 A.D., located A.D., located all the components of the computer from the central processing unit 18 unit and memory to input/output controls on a single In 1981 A.D.

4th Generation of computer
4th Generation of computer

IBM introduced its first computer for the home user, and in 1984 AD Apple introduced the Macintosh. Microprocessors also moved out of the realm of desktop computers and into many areas of life as more and more everyday products began to use microprocessors. As these small computers became more powerful, they could be linked together to form networks, which eventually led to the development of the Internet. Fourth generation computers also saw the development of GUIs, the mouse and handheld devices. IBM PC, Apple/Macintosh, SUPER BRAIN, STAR 1000, PUP 11 etc. are the examples of fourth generation computers.

  • Features of Fourth Generation Computer
    • Microprocessors were used as the main electronic component.
    • The size of computer became very much smaller.
    • The speed, accuracy and reliability of computers were improved.
    • It was a vast improvement over the third generation computer.
    • The operating speed of these machines is measured in picoseconds,
    • These computers were highly reliable and more accurate than second generation computers.
    • They had larger storage capacity. Magnetic disk is the comma source of external storage in these computers.

Fifth Generation of Computers

The fifth generation computer is on the way of development starting from present to future. The technology that will be used in these computers is BIO Chip also called Artificial Intelligence (ULSIC=Ultra Large Scale Integration Circuit). 

This technology was first developed by Japanese Computer Manufacturers Companies. Fifth generation computing devices, based on artificial intelligence, are still in development, though there are some applications, such as voice recognition, that are being used today. The goal of fifth-generation computing is to develop devices that respond to natural language input and are capable of learning and self-organization.

5th Generation of Computer
5th Generation of Computer
  • Features of Fifth Generation Computer
    • These computers will be based on biochips.
    • They will able to think and decide themselves.
    • These computers will be use parallel processing.
    • These computers will be used in intelligent robots.
    • These computers will have the ability to solve the problem themselves.
    • These computers will be able to recognize voice, images etc.
    • These computers will have extra high processing speed.
    • They will have the ability to communicate using natural languages.

History of Computers in Nepal

The first computer brought in Nepal was IBM 1401 in 2028 BS for the population census. Later in 2031 BS, Electronic Data Processing Center was established which was later called as National Computer Center. ICL 2950/10 was brought in Nepal for the population census of 2038 BS in aid of UNDP After 2039 BS, different microcomputers like Apple, Vector, Sirus were introduced in Nepal. From the time, computers have been used in different government sectors like banking, agriculture, universities and all private organizations.

TYPES OF COMPUTERS

Computers can be classified based on their principles of operation their configuration. By configuration, we mean the size, speed of doing computation and storage capacity of a computer. Since the application area of computers are not limited, computers used in different sector are of different types. A computer used at your home is somehow different from the computer used at banks to store banks database.

Types of Computers My Digital Nepal
Types of Computers

Broadly, computers are of two types, specific purpose and general purpose. Specific purpose computers can carry out only a specific task where as a general purpose computer can carry out a variety of tasks.

There are three different types of computers according to the principles of operation. Those three types of computers are:

  • Analog computer
  • Digital computer
  • Hybrid computer

Analog Computer

Analog Computer
Analog Computer

Analog computers work on continuous signals. Analog computers simply measure physical quantities (e.g. pressure, temperature, length etc.) and convert them into numeric values. For example, thermometer does not perform any calculations but measures the temperature of the body by comparing the relative expansion of mercury. Analog computers are mainly used to control scientific equipment and engineering purposes because they deal with quantities that vary constantly. They give only approximate results.

Digital Computer

Digital Computer
Digital Computer

Digital computers work on digital data. The general purpose digital computers uses discrete data can be in any form like letters, numbers, symbols and figures etc. These discrete data are processed in the form of binary digits. They are mostly used in home, office, school etc. Special purpose digital computers can be fixed permanently into the machine. For example, processors are installed in automobiles to control fuel, banking systems etc. Digital computers work on binary digits. All the operations in the digital computer are performed in sequential or one operation at a time. On the basis of size and processing speed, digital computers can be further classified into four types. They are:

  • Supercomputer
  • Mainframe computer
  • Mini computer
  • Microcomputer

Super Computer

Super Computer
Super Computer

Supercomputers are the largest and most expensive digital computers. Supercomputers contain several processors that work together to make it the most powerful and the fastest computer. They have a large memory capacity and very high processing speeds for solving scientific and engineering problems. They are mostly used to forecast the weather and global climates, biomedical research aircraft design, robots design, military research and other areas of science and technology. Seismograph, plasma and nuclear research in encrypting and decoding sensitive intelligence information are also other application areas of these computers. Examples: CRAY-XMP, NEC Super SXII, CYBER 205, SX-3, etc.

Mainframe Computer

Mainframe Computer
Mainframe Computer

Mainframe computers are next powerful computers specially designed As multi-user computer. They use several CPU for data processing and more than 100 users can use these computers at a time. They allow the user to maintain large information storage at a centralized location and can be able to access and process from different computers located at different locations. These computers are used in large business organizations, examination, industries, credit card processing, air traffic control system and security to process complex data. Examples: IBM S/390, ICL 39, IBM 3081, etc.

Mini Computer

Mini Computer
Mini Computer

Minicomputers are also multi user computers less powerful and smaller in size than mainframe computers. They support more than dozens of people at a time working in the various terminals of minicomputer. These are mainly used in university, large business organizations to process complex data. Examples: PDP-11 (Programmed Data Processor), VAX, IBM 9375, etc. 

Micro Computer

Micro Computer
Micro Computer

Microcomputers are the digital computers that works with a microprocessor. It is designed as a single-user machine i.e. only one user can work at a time. These are commonly used in offices, homes, schools, shops to perform different data processing jobs. Examples: IBM PCs, Apple Mac., IBM Compatible PCs, etc.

Hybrid Computer

Hybrid Computer

A hybrid computer is a type of computer that is designed to provide the features and functions that are found by both the digital and analog computers. A hybrid computer system offers a much cost effective method that is used to perform complex simulations. These computers are the combined form of analog and digital computers. These computers are used in industrial application, airplanes, ships, hospitals and in scientific research centers. Pulse Electrocardiogram (ECG), Echo cardiogram (ECHO), Ultrasound machine, CT-Scan machine etc are examples of hybrid computers used in hospitals.

A Computer System

Work Flow of Computer System
Work Flow of Computer System

A computer system is made up of two major components. They are Computer Hardware and Computer Software. There is nothing else in a computer system except hardware and software. There should be co-operation between hardware and software to perform any task by a computer. A computer cannot function in the absence of any of its components.

Hardware are the physical parts of the computer which make up the complete computer system whereas software are the logical parts that direct the hardware what to do and how to do.

You can compare the hardware to your physical parts of the body and software to the knowledge in your mind. Your body parts can be seen and touched but your knowledge in your mind cannot be touched and seen.

Computer Hardware

Computer hardware is the physical parts of the computer, which make up complete computer system. Hardware are those parts of computer system, which can be touched or felt physically. Therefore, hardware can be defined as: The physical parts of a computer system that you can touch, feel and see. In other words, Computer hardware is the electromechanical equipment which make computer system.

All the physical components of a computer such as a keyboard, mouse, monitor, system unit, CPU, printer, scanner, webcam, CD/DVD-ROM, etc. are examples of computer hardware.

Most of the hardware components such as motherboard, CPU, hard disk, RAM, ROM, etc. are contained inside the system unit so they are not seen outside. You can see only those components of computer which are outside the system unit such as a keyboard, mouse, monitor, speaker.etc.

  • Printer
  • Keyboard
  • Monitor
  • Mouse
  • Hard disk
  • Speaker
  • Joystick
  • Scanner

Some of the hardware devices are discussed below:

Input Devices

A computer cannot perform any task without giving data and instructions to it. We can give data and instructions to the computer using input devices. It is not possible to operate a computer without input devices. The input devices are used to enter data and instructions into the computer for processing.

The devices such as a keyboard, mouse, joystick, scanner, microphone, digital camera, webcam, etc. are known as input devices or input hardware. Today various types of input devices are used in computers. Some of the commonly used input devices are described below:

  • keyboard

Keyboard is the basic and fundamental input device of a computer. You can give input to the computer through keyboard. The input may be data such as letters, numbers, symbols and instructions. There are different types of keys on the keyboard. The keys on the keyboard are marked alphabets, numbers and other special characters.

Keyboard
Keyboard

The standard keyboards used in PC have 104 keys and the multimedia keyboards have more than 104 keys. The laptop computers have fewer keys. The different keys perform different functions. You can input data and instructions into a computer by pressing keys on the keyboard. Different companies are manufacturing keyboards with different layout. The most common English language key layout is the ‘QWERTY’ layout. 

  • Mouse

The mouse is another commonly used input device with GUI programs in the personal computer (PC). It is also called a pointing input device because it points any items seen in the monitor. Mouse is used to point objects and give commands to the computer. You can move objects, open them, change them, and perform other actions using mouse. When you move the mouse on the mouse pad, the mouse pointer on the screen moves in the corresponding direction. You can point objects moving this mouse pointer and select them by clicking or double clicking over them.

Computer Mouse
Computer Mouse

Generally, a mouse contains two buttons: a left button that is called the primary button and right button that is called secondary button. The primary button is the one you will use most often. Different buttons have different functions depending on the running program. The newly developing mouse also includes a scroll wheel between the buttons. That helps you to scroll through documents and long pages in websites more easily.

  • Joystick
Joystic
Joystic

Joystick is an input device. It is also a pointing input device like a mouse that is used to point and move objects on the screen. It is specially used for playing computer games. It has one or more push buttons through which we can play and control computer games. We can compare it with gear lever of motorcar.

  • Trackball
Trackball
Trackball

Trackball is similar pointing device like a mouse which consists of a movable ball in a socket. You can roll with your fingers or palm to move the pointer on the screen.  As you move the ball, the pointer moves on the screen in the same direction. It is mostly used on portable computers such as laptop, palmtop, notebook, etc. For pointing and choosing GUI icons.

  • Touch Screen
Touch Screen
Touch Screen

Touch Screen is a kind of video display screen that consists of touch sensitive display panel covering the screen. It is a screen with touch sensitive points or program Icons which you can use with your finger or a stylus. A stylus is a pen-shaped pointing tool. You can use your fingers to select objects on the screen and give commands to the computer like a mouse. It replaces the use of mouse or light pen as a pointing device. Touch screens are mostly used on portable computers such as laptop, palmtop, notebook, mobiles, Ipads, Iphones, etc.

  • Touch Pad
Computer TouchPad
Computer TouchPad

Touch Pad is one of the latest input devices consisting with a touch sensitive pad that is used as a pointing device. By putting your fingers on the touchpad, you can point the objects on the screen and give commands to the computer. This pad is also used in some portable computers such as laptop, palmtop, notebook, etc.

  • Scanner
Scanner
Scanner

A scanner is an input device that optically scans (copies) images, printed text, handwriting, or an object, and sends them to the computer. The scanner converts the images, printed text, handwriting, or an object into digital form (binary format) and sends to the computer for processing. The scanner can perform such a task which can not be done by keyboard and mouse. So, it is also called an indirect input device.

  • Web Camera
Web Camera
Web Camera

This is one of the latest inventions of computer hardware that takes photos or videos and sends into the computer. It is widely used in Internet chatting and video conferencing. It is specially used in messenger programs such as Yahoo! Messenger, Windows Live Messenger and Skype. It is connected to a computer often using a USB (Universal Serial Bus) port.

  • Microphone
Microphone
Microphone

A microphone is an input device that is used to input voice or sound into the computer. You can record speech, songs, etc. in the computer using a microphone. A computer stores recorded voice and sound in the digital format so that they can be processed as required.

Processing Devices

The Central Processing Unit (CPU) Is main processing device of the computer. It is also called microprocessor. The microprocessor can be considered as the brain of the computer. The microprocessor performs all the arithmetic and logical operations on the computer. It processes the data according to the given instructions and gives result. The processing speed of the computer also depends on the microprocessor. The modern CPUs are small square in shape and contain multiple metallic connectors called pins on the underside.

The devices which are used to process the input data according to the given set of instructions are called processing devices.

Central processing Unit (CPU)
Central processing Unit (CPU)

Parts of Microprocessor (CPU)

Basically the microprocessor has three main parts. They are:

  • Control Unit (CU)
  • Arithmetic Logic Unit (ALU)
  • Registers
  • Control Unit (CU)

The control unit controls and coordinates all the activities of the computer system. It directs all the parts of a computer system to perform their tasks. The control unit controls the execution of instructions given to the computer. It also controls the movement of data inside as well as outside the CPU. The control unit coordinates to receive data and instructions from the input device and stores them in the main memory. It communicates between ALU registers.and memory. It. also communicates between the CPU and all input, output and storage devices. So, it can be considered as the manager of the CPU.

  • Arithmetic Logic Unit (ALU)

The Arithmetic Logic Unit (ALU) performs all the arithmetic and logical operations on the computer. In arithmetic operations, ALU performs the addition, subtraction, multiplication and division of numeric data. In logical operations, ALU compares the numerical data as well as alphabetic data. For example, it checks whether the first number is greater than the second, less than the second or equal to the second, the first string is longer than the second string, similarly shorter than second string, etc. 

  • Registers

The CPU also consists of a number of registers in it. It is a temporary storage device which holds data and instructions as long as it is being interpreted and executed. The register can contain the address of memory location of data rather than the actual data itself. When the data and instructions are fetched from main memory for processing then these data have to be stored in one of the registers of the CPU.

Output Devices

Computer gives result after processing raw data, which is called output. The output devices are used by computer to give its result of processing. The output devices give the output in human understandable format. The output may be in the form of text, picture, graphics, audio and video. The monitor and printer are the most commonly used output devices. Some other output devices are speaker, plotter, projector, etc.

The devices, which are used to give the processed result (output) of the computer are called output devices. The following are the common output devices used to display result of computer processing.

  • i. Monitor
Monitor
Monitor

Monitor is a primary output device of the computer. It is a compulsory part of computer system. It is also called the Visual Display Unit (VDU) that provides visual output on the screen. It displays the output in the form of text, pictures and video. The output displayed on the monitor screen is known as soft copy output because the output will be for temporary purpose. A monitor has different control buttons that allows you to adjust the brightness and color contrast on the screen.

Now-a-days monitors are available in three main types. They are:

  • Cathode Ray Tube (CRT) Monitor
  • Liquid Crystal Display (LCD) Monitor
  • Light Emitting Diode (LED) Monitor
  • ii. Speakers
Speaker
Speaker

The speaker is an output device, which produces sound from the computer. Speakers allow you to listen to music and hear sound effects from your computer. The speakers are used to play music and songs from the computer. Some speakers are also inbuilt inside the system unit and they give different sounds while using computer.

  • iii. Printer

Printer is the basic output device that is used to print the output on the paper. The output printed on the paper is called hard-copy output because the printed-output-will.be long term permanent purpose. Different types of printers are available in the market. Some of the most commonly used printers are dot matrix printer, inkjet printer and laser printer, Dot Matrix Laser Inkjet 

Printer
Printer
  • Dot Matrix Printer:

This is an ordinary type of printer which prints text and graphics on paper by physically striking pins against an inked ribbon. The inked ribbon is placed between the print head he paper. The more pins, the better the print quality. The printing speed of this printer is slow and it produces low quality of print.

  • Inkjet Printer:

This is a type of printer which prints text and graphics on the paper by spraying small drops of ink into paper. It is quite faster and produces very high quality of print than dot matrix printer. Inkjet printers are the most common type of printer. 

  • Laser Printer:

It is the most widely used printer today. The laser printer uses a laser beam to print high quality text and graphics on the paper. The printing speed of this printer is higher than dot matrix and inkjet printers. It produces a high quality of print than dot matrix and inkjet printers.

Memory and Storage Devices

The devices which are used to store data and program in the computer is called storage or memory devices. The storage or memory devices can be categorized into two types. They are:

  1. Primary Memory or Main Memory
  2. Secondary Memory or Storage Devices
Primary Memory or Main Memory

The primary memory is also known as the main memory or internal memory of the computer. It stores data and instructions for processing while executing the program. It communicates directly with the CPU. The primary memory is fixed on the motherboard inside the casing box. There are two types of primary memory.

  1. Read Only Memory (ROM)
  2. Random Access Memory (RAM)
  • a. Read Only Memory (ROM)

ROM is permanent memory of the computer. It is called non- volatile memory. It provides startup instructions when the computer is turned on. The instructions in ROM are stored at the time of manufacturing of the computer. The instructions stored in ROM cannot be changed by the user. We cannot store any data into the ROM. We can only read data from it.

  • b. Random Access Memory (RAM)

RAM is the temporary memory of the computer. The data stored in RAM are lost forever when the computer is turned off, RAM is also called volatile memory. This is the memory where data and program instructions are stored while the computer is in operation. So, it is considered CONNAIM as working memory of the computer. We can read data from it. write data into it, too.

Difference Between RAM and ROM
RAMROM
It stands for Random Access
Memory.
It stands for Read Only Memory.
It is a volatile or temporary memory. It is non volatile or permanent
memory.
It is comparatively expensive. It is comparatively cheaper.
It is startup memory of the computer which stores the startup information. It is working memory of computer which stores data being currently processed.
Secondary Memory/ Storage Device

The secondary memory is also known as storage devices. The data stored in secondary memory do not get erased when the computer is turned off. When you store some data on the second stored there until you erase them. The commonly used secondary memory devices Hard disk, Floppy disk, CD-ROM, DVD-ROM, Pen drive, etc.

  • Hard disk
Hard Drive
Hard Drive

Hard disk is the main and the largest data storage device in the computer. It is also called the HDD (Hard Disk Drive), hard drive or fixed disk. It can store a large amount of data permanently. It is fixed inside the casing box and connected to the motherboard with a data cable. The operating system software, other programs and most other files are stored in the hard disk.

  • Floppy Disk (Diskette)
Floppy Disk
Floppy Disk

Floppy disks also called floppies or diskettes. It is a very popular magnetic storage disk of early days. It is a light and portable secondary storage device. The floppy disk is used to transfer small amount of data from one computer to another. We can read data from floppy disk and also write into it. A floppy disk drive is needed to read data from floppy disk and write into it. Floppy disks are going to be outdated. Now instead of floppy disks CDs, DVDs and Pen drives are used to store and transfer data. Compared to CDs and DVDs, floppy disks can store only a small amount of data. They also retrieve information more slowly and are more prone to damage. For these reasons, floppy disk drives are less popular than they used to be, although some computers still include them. 

Floppy disks are available in different sizes and capacities. The most common size of floppy disk is 3.5″ in diameter and it has a storage capacity of 1.44MB. (Megabyte)

  • CD-ROM
CD ROM
CD ROM

Compact Disk Read Only Memory is an optical device which is the most popular and widely used storage. It uses laser beams to read data from it and to write data into it. It has large storage capacity than floppy disks. The normal CD-ROM can store up to 700 MB of data. We can read data from it and also Inkscape Vector Graphic harte write data into it. 

A CD-ROM drive is required to read data from it and to write data into it. Nowadays CDs are most commonly used for storing programs (Software) music, video, The Classic Archives films, games or data files for personal computer. They are cheaper and portable to use.

  • DVD
DVD
DVD

DVD stands for Digital Versatile Disk or Digital Video Disc. A DVD is also an optical disk but it has very high storage capacity than CD-ROM. A DVD looks like CD but it is developed for a Compact Digital Video format. Its storage capacity ranges from 4.7 GB to 200GB. A single sided DVD can normally store up to 4.7 GB (Gigabytes) of data. Like CD, we can read data from it and also write data into it. A DVD-ROM drive is required to read data from it and to write data into it. Nowadays, DVDs are the most widely used for storing software, 16GB games, music, videos and data.

  • Pen Drive (USB flash drive)
USB Pend Drives
USB Pend Drives

Pen drive is also called flash drive, or USB (Universal Serial Bus) drive or Thumb drive. It is small in size and can be carried in a pocket like a pen so it is named as pen drive. It is a very popular and most widely used storage device today. It is a convenient way of transferring data from one computer to another. It can be considered as a small external hard disk. Its storage capacity ranges from 128Mb to a few Gigabytes.

Important Points to Remember

  • A computer system is made up of two major components: Hardware and Software.
  • Hardware are the physical parts of the computer which make up the complete computer system.
  • Basically, computer hardware can be divided into four categories: Input Devices, Processing Devices, Output Devices and Storage/ Memory Devices.
  • The devices that are used to enter data and instructions into the computer are called input devices.
  • The devices which are used to process the input data according to the given set of instructions are called processing devices.
  • The Central Processing Unit (CPU) is the main processing unit of the computer.
  • The devices, which are used to give the processed result of the computer are called output devices.
  • The output displayed on the monitor and the output produced by the speaker is called softcopy output. 
  • The output produced by the printer by printing on the Paper is called hard copy output.
  • The devices which are used to store data and program in the computer are called storage or memory devices.
  • The primary memory stores data and instructions for processing while executing the program.
  • The secondary storage also known as permanent storage, which stores data, program, software etc. for future purpose.

COMPUTER SOFTWARE

A set of instructions written to instruct the computer to solve a particular, problem is called a program. A set of such program is known software. Computer software is a collection of computer programs and related data that provides the instructions for telling a computer what to do and how to do it.

operating-system-OS
operating-system-OS

Software is an organized collection of programs which is responsible for controlling and managing the hardware components of a computer system to perform specific tasks. Software is the invisible part of computer system which users can’t touch. It is non-touchable part of computer that makes the computer hardware to function in order to perform tasks. The software guides and controls the hardware to carry out the instructions to perform the different operations in computer system. Microsoft Word, Microsoft Excel, Adobe Page Maker, Adobe Photoshop, Linux, Windows 7/8, etc., are the examples of computer software.

Types of Computer Software

Computer software can be classified into two categories. They are.

  1. System software
  2. Application software
System software

System software is a collection of programs that controls and manages the internal operation of the computer. It is designed to operate the computer hardware, to provide basics functionality, and to provide platform for running application software. System software works as the interface between hardware and the users. System software refers to the files and programs that make up your computer’s operating system. Depending on the basis of functionality, system software can be classified as follows:

System-Software
System-Software
  • Operating System Software
  • Utility Software
  • Programming Language Translators
Operating System Software

An operating system (OS) is a collection of software that manages computer hardware resources and provides its users with an interface. So, every computer needs to have its own operating system, which takes care of the effective and efficient utilization of all the hardware and software components of the computer. It is the master controller for all the internal operations of the computer system.

Every operating system performs the basic functions such as managing resources, providing user interface and running application. The operating system in the computer works like an interface between a user and application software. Some popular operating systems are MS-DOS, Windows 98, Windows XP, Windows 7/8, Windows Vista, Windows NT Server, Windows Advanced Server 2003, Novell Netware Server, Mac OS X, Linux, Unix etc.

Some basic functions of an operating system software are:

  • It provides easy interaction between a user and a computer.
  • It starts the computer and controls its entire functioning.
  • It controls and manages input/output devices.
  • It manages various types of memories such as primary, secondary, cache, etc.
  • It interprets and executes the commands of application programs.
  • It provides platform to run other software programs.
  • It provides security to users’ jobs and files.
  • It allows users to share data and software among themselves
  • It notifies the users about any fault that may occur in the computer.

Types of Operating System

The operating system is divided into two types. They are:

  1. Single User Operating System
  2. Multi User Operating System

Single User Operating System

As the name implies, Single-user-operating system is designed to manage the computer so that a user can effectively do one thing at a time. The Palm OS for Palm handheld computers is a good example of a modern single-user, single-task operating system. This is the most common type of OS used on a home computer, as well as on computers in offices and other work environments. There are two general types of single-user operating system: single task and multitasking systems. MS-DOS, Windows 3X, Windows 95/97/98 are examples of single user operating system.

Multi User Operating System

A multi-user operating system allows multiple users to use the same computer at the same time and / or different times. In other words, a multi-user operating system is a computer operating system (OS) that allows multiple users on different computers or terminals to access a single system with one OS on it. These programs are often quite complicated and must be able to properly manage the necessary tasks required by the different users connected to it. Windows NT Server Windows Advanced Server 2003, Novell Netware Server, Mac OS X, Linux, Unix are examples of multi-user operating system.

Programming Language Translator

Programming Language translator or language processor is a type system software that translates programs prepared by program any other languages into machine language. It converts the programming instructions written in human convenient form into machine language. codes that computers understand and process. The programs written in any programming language needs to be converted to binary form using language translator.

Language translators are classified into three types:

  •  Assembler
  •  Interpreter
  •  Compiler

Assembler

Assembler is a type of language translator that translates programs written in assembly language into machine or low-level language. The assembly language program is called source code and the machine language program is called object code. The assembler takes the source code as input and translates it into object code for processing.

Interpreter

Interpreter is a type of language translator that translates program written in high level language (human language) into machine language line by line or statement by statement. After the translation of first statement of the program then only it translates the next statement of the program and so on. In other words, an interpreter translates a statement in a program and executes the statement immediately before translating the next source language statement.

During the converting of the statement, if any error occurs then it immediately shows the error message and terminates the execution of the next statement. Some of the programming languages such as GWBASIC, QBASIC, LISP, LOGO etc. use interpreter language translator.

Compiler

Compiler is a type of language translator that translates program written in high level language into machine language in a single operation. It reads all the statements of the program and translates the source code into machine code (binary form). During the complication the program, if any error is found then it reports all the errors of the program along with the line numbers at the end of complication.

Some programming languages such as C, C++, Visual Basic, Java, FORTRAN etc. use compiler as language translator.

Packaged Software

Packaged software is a type of generalized set of application software that allows the computer to perform specific task for different users. It is user friendly ready-made program designed to meet the common requirements of a wide variety of users for particular type of work in more than one environment.

Some examples of the most commonly used packaged software are: word processing software, spreadsheet software, presentation software, database software, graphics software, multimedia software, accounting software etc.

Customized or Tailored Software
Customized or tailored software
Customized or tailored software

Customized or Tailored software is a type of specialized set of application software designed to meet the specific requirements of an organization or individual. It is developed on the demand of only single organization or user to satisfy their needs and such software that may not be useful for another organization or user. Some examples of customized software are: school management software, telephone bill processing software, air ticket reservation software, payroll software, SEE result processing software, hospital management software etc.

DATA COMMUNICATION AND COMPUTER NETWORK

Data Communication

The word communication means sending and receiving information between two or more devices or persons through different medium Telecommunication is a system of sounds, images, texts or data in the form of electronic signals transferred through the communication mediums. The fastest growing field of telecommunication is data communication.

Data Communication
Data Communication

A data communication system is a collection of hardware, software and other devices that allows exchanging data, information between two or more devices through wire or wireless mediums. Communication can be in one direction or both directions.

Computer Network

A computer network is simply two or more computers connected together so they can exchange information. A small network can be as simple as two computers linked together by a single cable or it may be a group of several computers connected at a central networking device through wired or wireless medium.

Computer Network
Computer Network

A computer network is a group of interconnected computers through transmission media in order to communicate and share resources. The computer in a network can be connected within room or building or different places with the help of wires or wireless media. When computers and other resources are interconnected, they can share data, hardware, software.

Advantages of computer network

The advantages of computer networks are:

  1. communication is easy and fast. 
  2. Data and software sharing are possible.
  3. Sharing of hardware devices like printers, hard disk, DVD drives, Scanner, MODEM etc.
  4. Sharing and transferring files within networks.
  5. The network computers can communicate with each other.
  6. Only authorized user can use the facilities of the network.
Computer Network Components

There are different components of a network. Following are the basic components of network.

  • Server
  • Workstation
  • Network Adapter
  • Transmission Media
  • Cable connectors
  • Network Connecting Device
  • Network Operating System
Server
Server
Server

A server computer is a powerful computer that controls and manages other computers and computing devices on the network. It provides Internet services such as print service, file Clients Vice, web service etc. to the other Server computers on the network. The Important data or information can be Stored on the server computer and other computers on the network can access the data whenever needed.

Workstation
Computer Workstation
Computer Workstation

A workstation computer is a computer on the network that uses the services provided by the server computer. It is the computer which is used by client in order to perform application tasks and also known as client computer. The client is less powerful than server.

Network Adapter
Network Adapter
Network Adapter

Network adapter or network interface card (NIC) is a circuit board with the components necessary for sending and receiving data. The NIC provides the physical connection between the network and the computer workstation through communication media. Most NICs are internal, with the card fitting into an expansion slot inside the computer. Nowadays, it is built-in on the computer motherboard.

Transmission Media

A transmission media is a channel through which data or signals can be transmitted from one point to another. It is a physical connection between the devices on a network. Basically, there are two types of transmission medium: Guided (wired) and Unguided (wireless).

Transmission Medium
Transmission Medium

Guided Transmission Media uses a “cabling” system that guides the data signals along a specific path while Unguided Transmission Media transfers the data without using any cables in the form of radio frequency (RF) signals.

  1. Twisted Pair Cable
  2. Coaxial Cable
  3. Fiber Optic Cable
Cable Connectors

A cable connector is a connecting device that physically connects network cable to the network device like NIC. Hub, switch etc. it is attached at both sides of the network cables. The cable with Connectors is joined at the port of the networking device. Different types of connectors are used to join the cables with the network interfaces of nodes (computer, hub, switch etc.).

  • BNC
  • ST Connector
  • RJ-11 (Telephone)
  • RJ-45
  • BNC (Bayonet Neill-Concelman) T-connector
  • ST Connector
Network Connecting Devices

Physical parts and devices used to connect computers in the network environment are called network devices. Some basic network connecting devices are discussed below:

MODEM (Modulator-Demodulator)

A modem is a network connecting device that directly converts digital signal from a computer or other digital devices into analog form for transmission over analog link (telephone line) and vice versa. It is a device that connects a personal computer to the network through the telephone line. There are two zoom types of modem. They are Internal and External modem.

MODEM
MODEM

Internal modem is circuit board that plugs into one of the expansion slots on the motherboard. External modem is kept outside the computer. The different modems are:

  • Analog Modem
  • Digital Subscriber Line (DSL) Modem
  • Integrated Services Digital Network (ISDN) Modem
  • Cable Modem
  • Asymmetric Digital Subscriber Line (ADSL) Modem
Hub
Internet Hub
Internet Hub

A hub is a network connecting device with multiple points or ports. It is used to connect computers or other network devices through its ports. Each port on the hub accepts one end of the network cable with connector running from a computer. So, the hub connects more than one computer in order to form a Link network. A hub forwards the data or signals to the computers connected with it.

Switch
Network Switch
Network Switch

A switch is a network connecting device that has multiple connecting ports like a hub. It is used to connect computers, network devices and network segments. It can determine the source and destination so it can forward data to the particular computer only. So, it reduces the amount of unnecessary network traffic improves the network performance. Because of this smart feature, switch is also known as smart Hub.

Network Operating System (NOS)
network operating system-NOS
network operating system-NOS

Network Operating System is a multi-user computer operating that is designed primarily to support workstations, servers and other networking devices. Windows NT, Windows Server, Novell’s Operating system Netware, Linux, UNIX etc. are examples of network operating systems.

Type of Computer Network

Computer network is classified on the basis of scope and the role of individual computers in the network, the size of the network, the distance it covers and the type of line used in communication. They are: 

  • Local Area Network (LAN)
  • Metropolitan Area Network (MAN)
  • Wide Area Network (WAN)
Local Area Network (LAN)

The Local Area Network LAN) is a small network of Computers that are relatively near with each other. LAN is a type of computer network where computers are connected within rooms, buildings or local area with the help of wire or wireless medium to share resources among each other. The LAN where wireless media are used is known as Wireless Local Area Network (WLAN). The networks of computers in an office room, cyber are the examples of the LAN.

Local Area network-LAN
Local Area network-LAN

Features of LAN:

  • Owned by a single organization.
  • Diameter of not more than three kilometers.
  • It is not affected by environmental factors.
Metropolitan Area Network (MAN)

The interconnection of computers within a city or in between Boring cities is known as Metropolitan Area Network (MAN). It is a combination of two or more individual Local Area Networks but with criterion of the boundary of the network not exceeding the city limits. Metropolitan Area Network is basically an extension of the Local Area Network except for the fact that the size of the network extends to very large area. The network between bank and its branches, school and its branches within city or neighboring cities are examples of the MAN.

Metropolitan Area Network-MAN
Metropolitan Area Network-MAN

Features of MAN:

  • Owned by a single or multiple organization.
  • The transmission speed can be higher for shorter distances.
  • Include one or more LANS as well as telecommunications equipment.
Wide Area Network (WAN)

The interconnection of computers within a country, neighboring countries or continents is known as Wide Area Network (WAN). The WAN Covers a very large geographic area i.e. the whole world. In the WAN, computers are interconnected using telephone line, microwave, Client Server radio wave or satellite communication system. The Internet is an example of Wide Area Network.

Wide Area Network-WAN
Wide Area Network-WAN

Features of WAN:

  • Owned by multiple organizations.
  • Covers a large geographical area.
  • It may be disturbed by environmental factors.
Network Topologies

The cabling structure of interconnected computers in LAN is known as network topology. It is also known as LAN topology. The LAN topology describes how the computers are connected with the help of wires and the data flow from one computer to another. There are three basic topologies. They are Bus, Ring and Star.

Bus Topology
Bus Topology
Bus Topology

Bus topology is a type of LAN topology where all the nodes on the network are connected through a single communication line called bus or trunk in linear form. It uses a common backbone to connect all the network devices in a network. A single cable is actually the small Terminator  segment of the coaxial cables connected with Node the help of T-connectors at both sides of the main cable.

Ring Topology
Ring Topology
Ring Topology

A ring topology is a network topology where all the nodes on the network are connected to each other in the form of ring or circle without any end point. In this topology, the signal travels in a circle passing through each computer on the network because there are no terminated ends to the cable. Each device in the network that is also referred to as node handles every message that flows through the ring. Each node in the ring has a unique address. It supports coaxial, twisted pair, and fiber optic cables.

Star Topology
Star Topology
Star Topology

A star topology is a network topology where all the nodes on the network are connected through a central device called a hub or switch. In the computer networking world, the most commonly used topology in LAN is the star topology. In this topology all the nodes are separately connected with the help of different length of twisted pair cables. Data on a star network passes through the central device that manages and controls all functions of the network.

Internet

The Internet is the largest computer network that connects millions of computers around the world. Internet is a global collection of high-powered computers that are connected to each other with network cables, telephone lines, microwave dishes, satellites etc. It connects several thousand computer networks all over the world. So, it is known as network of networks. The internet is an information superhighway and has logically connected the world into a cyber village.

Internet
Internet
Services of the Internet

Some important services provided by the Internet are:

  • World Wide Web
  • Electronic Mail
  • E-commerce
  • Video conference
  • Internet Relay Chat
  • Uploading and Downloading
World Wide Web

The World Wide Web (WWW) is one of the most popular services of the Internet. WWW is a huge collection of pages of information linked to each other around the globe on various topics. It allows the user to exchange and share data through the Internet using a protocol known hypertext Transfer Protocol (HTTP). It is also known as the Web. information on the web is presented in the form of web pages. Each pages can be a combination of text, pictures, audio clips, video clips, animations, and other electronically presentable hyperlinked material.

E-mail

E-mail or Electronic mail is one of the most popular services provided by the Internet. It can be defined as the exchange of messages and computer files between computers over a computer network. E-Mail is the world’s largest electronic message system that is transferred from one computer to another through the Internet.

E-commerce

E-Commerce is also one of the important services of Internet through which you can sell or buy goods. In simple terms, it is doing business through the Internet or doing business virtually. You can use the e-commerce service of the Internet through some special web sites. Some e-commerce sites are: kaymu.com.np, muncha.com.np, eBay. com, amazon.com, alibaba.com, meroshopping.com, kinmel.com, www.sajhapasal.com etc.

Internet Relay Chat (IRC)

Internet Relay Chat (IRC) or simply chat is one of the services provided by the internet that allows people to communicate with each other in real time. It supports people at different locations to send and receive both text and instant voice messages.

Internet Relay Chat (IRC)
Internet Relay Chat (IRC)
Video Conference

Video conference is popular and extends service of the internet through which the people at different locations can communicate with each other in real time face to face, it uses the same technology of IRC including text and pictures.

Uploading and Downloading

Uploading and Downloading is the important services of the Internet that allows the user to transfer a large volume of file from one computer to another through File Transfer Protocol (FTP). The process of copying a copy of a file or document or program etc. from a user’s computer to the remote computer (Web Server) is called uploading. 

The process copying a copy of a file or data or program etc. from a remote computer (Web Server) to the requesting computer (user’s computer) is called downloading.

Telnet

Telnet is one of the simplest tools or facility of the Internet that allows user to use a remote computer (far distance computer) through Internet. When the Telnet program connects your computer to the remote computer, the remote computer usually asks you to enter a username and password.

Number System

Number system is a basis for counting various items. On hearing the word ‘number’, all of us immediately think of the familiar decimal number system with its 10 digits: 0,1,2,3,4,5,6,7,8 and 9.

Modem computers communicate and operate with binary numbers which use only The digits 0 and 1. Let us consider decimal number 18. This number is represented in binary as 10010. In the example, if decimal number is considered, we require only two digits to represent the number, whereas if binary number is considered we require five digits. Therefore we can say that, when decimal quantities are represented in binary form, they take more digits. 

For large decimal number people have to deal with very large binary strings and therefore, they do not like working with binary number. This fact gave rise to three new number system: octal, Hexadecimal and Binary Coded Decimal (BCD). These number system represents binary number in compressed form. Therefore, these number systems are now widely used to compress long strings of binary numbers.

Before, considering any number system, let us consider the familiar decimal number system In decimal number system we can express any decimal number in units, tens, hundreds, thousands and so on. When we write a decimal number say, 5678.9 we know it can be represented as:

5000 + 600 + 70 + 8 +0.9=5678.9

The decimal number 5678.9 can also be written as 5678910 where the 10 subscript indicates the radix or base. In power of 10, we can write as

5 x 10^3 + 6 x 10^2 + 7 10^1+ 8 x 10° + 9 x 10^-1

This says that, the position of a digit with reference to the decimal point determines its value/weight. The sum of all the digits multiplied by their weights gives the total number being represented. The leftmost digit, which has the greatest weight is called the most significant digit and the rightmost digit, which has the least weight, is called the least significant digit.

Special Notes: Number system refers to the digits, its arrangements, positional value and base of the number system.

Introduction to positional and non-positional number system

Normally, number system is categorized into two types: positional number system and non-positional number system. In positional) number system, each digit of a number has its unique positional weight or place value. Examples of positional number system are decimal, binary, octal, hexadecimal etc. In non- positional number system, each digit/symbol of a number has no positional weight or place value. Example of non-positional number system is Roman Number System. 

There are basically two number systems

  1. Non-positional Number System
  2. Positional Number system

Non-Positional Number System:

Non positional number systems were used in the early days of human civilization. People used to count any things on fingers. When ten fingers were not adequate, stones, pebbles or sticks were used to indicate the values. In this system the symbols such as

I for 1,

II for 2

III for 3

IIII for 4

IIIII for 5 etc…

Each symbol represents the same value, regardless of the position in the number and we symbols are simply added to find the values of a particular number. It is not easy to perform arithmetic operation in this number system so the positional number systems were developed.

Positional Number System:

The positional number system is one in which the position of a number represent different values depending upon the position they occupy in the number. There are only few symbols are used, And the value of each digit is determined by three considerations.

  1. The digit itself
  2. The position of the digit in the number
  3. The base of the number system.

Special Note: A digit/bit having maximum positional weight is called Most Significant Digit (MSD)/Most Significant Bit (MSB) and a digit having minimum positional weight is called Least Significant Digit (LSD)/Least digit or bit is called LSD or LSB. Significant Bit (LSB). In other words, the leftmost digit or bit is called MSD or MSB and the right most digit or bit is called LSD or LSB.

The characteristics of positional number systems are

  • The value of the base determines the total number of different symbols or digits available in the number system and the first digit is always zero (0).
  • The maximum value of a single digit is always equal to one less than the value of the base.
Types of Positional Number System
  1. Decimal Number System
  2. Binary Number System
  3. Octal Number System
  4. Hexadecimal Number System
Decimal Number System

The decimal number system is very popular in our day-to-day life. In decimal number system ten symbols are used and the base of the system is equal to 10. The ten symbols or digits are (0, 1. 2. 3. 4, 5, 6, 7, 8 and 9). The first symbol or digit is 0 and the last symbol or digit is 9 (one less than the base), Each position in a decimal number represents a power of base (10). Right most position is the upit (10^0) position, the second position from the right is the tens (10^1) position, the third position from the right is the hundred (10^2) position, the fourth position from the right is the thousand (10^3) position and so on.

Things to Remember (TTR): A number system having base 10 is called decimal number system.

Following are the characteristics of a decimal number system.

  • Uses ten digits 0,1,2,3,4,5,6,7,8, and 9.
  • Called base 10 number system.
  • Radix (r) = 10
  • Symbols = 0 through r-1 =0 through 10-1 = {0, 1, 2… 8,9}
  • Each position in a decimal number represents a 0 power of the base (10). Example: 10°
  • Last position in a decimal number represents an x power of the base (10).
Binary Number System

Binary number system is one whose base is 2. That means there are only two symbols or digits (0 and 1) are used. The first digit is 0 and the next digit or last digit is 1 (one less than the base). Each position in a binary number represents a power of base (2). Right most position is the unit (2^0) position, the second position from the right is the two’s (2^1) position, the third position from the right is the fourth’s (2^2) position, the fourth position from the right is the eight’s (2^3) position and so on.

Things to Remember (TTR): A number system having base 2 is called binary number system

Following are the characteristics of a binary number system.

  • Uses two digits, 0 and 1.
  • Called base 2 number system
  • Radix (r) = 2
  • Symbols = 0 through r-1 = 0 through 2-1 = {0, 1}
  • Each position in a binary number represents a 0 power of the base (2). Example: 2°
  • Last position in a binary number represents an x power of the base (2). Example: 2^x where x represents the last position – 1.
  • Digits in a binary number are called bits (Binary digits).

A binary numbers are expressed with a string of 1’s and 0’s and, possibly, a binary point within it. The decimal equivalent of a binary number can be found by expanding the number into a power series with a base of 2.

Octal Number System

Octal number system is one whose base is 8. Eight symbols or digits (0, 1, 2, 3, 4, 5, 6 and 7) are used. The first digit is 0 and the last digit is 7 (one less than the base). Each position in an octal number represents a power of base (8). Right most position is the unit (8^0) position, the second position from the right is the eight (8^1) position, the third position from the right is the sixty fourths (8^2) position, the fourth position from the right is the five hundred twelve (8^3) position and so on. 

Things to Remember (TTR): A number system having base 8 is called octal number system.

Following are the characteristics of an octal number system.

  • Uses eight digits 0,1,2,3,4,5,6, and 7.
  • Called base 8 number system.
  • Radix (r) = 8
  • Symbols = 0 through r-1 = 0 through 8-1 {0, 1, 2…6, 7}
  • Each position in an octal number represents a 0 power of the base (8). Example: 8°
  • Last position in an octal number represents an x power of the base (8). Example: 8^x where x represents the last position – 1.
Hexadecimal Number System

Hexadecimal number system is one with base is 16. That means there are 16 symbols or digits (0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E and F) are used. The first ten digits are decimal number and the remaining six digits are denoted by the symbol A, B, C, D, E and F representing the decimal values 10,11,12,13,14, and 15. The first digit is 0 and the next digit or last digit is F (15) (one less than the base). Each position in a hexadecimal number represents à power of base (16). Right most position is the unit (16^0) position, the second position from the right is the sixteen’s (16^2) position, the third position from the right is (16) position, the fourth position from the right is (16^3) position and so on.

Things to Remember (TTR): A number system having base 16 is called Hexa-Decimal number system.

Following are the characteristics of a hexadecimal number system.

  • Uses 10 digits and 6 letters, 0,1,2,3, 4, 5, 6, 7, 8, 9, A, B, C, D, E and F.
  • Letters represent numbers starting from 10. A = 10, B = 11, C = 12, D = 13, E= 14, F = 15.
  • Called base 16 number system.
  • Radix (r) = 16
  • Symbols = 0 through r-1 = 0 through 16-1 = {0, 1, 2…9, A, B, C, D, E, F}
  • Each position in a hexadecimal number represents a 0 power of the base (16). Example 16°

NUMBER BASE CONVERSION SYSTEM

The human beings use decimal number system while computer uses binary number system. Therefore, it is necessary to convert a decimal number into its equivalent binary while feeding number puter and to convert binary number into its decimal equivalent while displaying result of in to the human beings. However, dealing with large quantity of binary numbers of many bits is inconvenient for human beings. Therefore, octal and hexadecimal numbers are used as a shorthand means of expressing large binary numbers. But it is necessary to keep in mind that digital circuits and systems work strictly in binary; we are using octal and hexadecimal only as a convenience for the operation of the system. Before going to see conversions between binary, octal and hexadecimal numbers we see the number of digits in several systems. Table 1.3 shows the decimal, binary, octal and hexadecimal numbers.

Decimal Number(Base-10)Binary Number(Base-2)Octal Number(Base-8)Hexadecimal Number(Base-16)
0000000
1000111
2001022
3001133
4010044
5010155
6011066
7011177
81000108
91001119
10101012A
11101113B
12110014C
13110115D
14111016E
15111117F

ASCII Character

  • The acronyms ASCII stands for American Standard Code for Information Interchange.
  • Latest coding system that represents the character of different language.
  • When a key is pressed on the keyboard, ANSI standard is used for converting the keystroke into the corresponding bits.
  • ASCII was developed by American National Standard Institute (ANSI).
  • Used to represent character.
  • Each character is coded as a byte (combination of eight bits).
  • It was originally 7-bit code and it is possible to 128(2^7=128)
  • Different arrangement with seven bits. That is ASCII-7 represents 128 character and ASCII-8 represents 256 characters.
  • But nowadays It is an 8-bit code possible to 256(29=256) different arrangement with eight bits and commonly used with microprocessor for representing alphanumeric codes.
  • Out of the 8 bits first seven bits are used to represent character while the eight bits is used to test for errors in communication system referred to as a parity bit. 
  • 8th bit is unused (or used for a parity bit)
  • The parity bit can be set to 1 or 0 so that the number of 1-bits in the byte is always
  • odd or even.
  • The practical use of ASCII characters can be observed from the way in which the letter (A, B, C…….), numbers (0, 1. ……) and other characters (-? @!) are typed from keyboard and are converted to a format readable by the computer.

ASCII code for number 0 to 9

DigitDecimalHexadecimal
048D30H
149D31H
250D32H
351D33H
452D34H
553D35H
654D36H
755D37H
856D38H
957D39H

Bit (Binary Digit)

  • Only two possible values/ two stable state i. e. O or 1.
  • The smallest unit of data on a binary computer is a single bit.
  • A single bit is capable of representing only two different values such as zero (0) or one (1), true or false, on or off or right or wrong etc.

Nibble

  • A nibble is a collection of 4-bits on a 4-bit boundary.
  • 4 bits=1 nibble or half byte (4 bits) = 1 nibble.
  • With a nibble we can represent up to 16 distinct values.
  • Bit at position 0(right most) is known as the Least Significant Bit (LSB). Similarly, bit at the leftmost position is called Most Significant Bit (MSB). All other bits are referred by their respective bit number.

Bytes

  • Bytes are a unit of computer memory.
  • The combination of eight (8 bit=10000000= 1 byte) bit is called Byte.

BCD (Binary Coded Decimal):

  • Stands for Binary Coded Decimal.
  • Defined by IBM for one of it’s early computer.
  • BCD computer could work only uppercase letter.
  • Combination of four bits pattern.

Unicode

Unicode is a universal encoding system to provide a comprehensive character set and was created by the Unicode consortium (a group of multilingual software manufacturers). Unicode simplified software localization and improves multilingual text processing. It overcomes the difficulty inherent in ASCII and extended ASCII.

Unicode typically uses 16 bits to store a character. This allows for the unique representation of characters in all languages and platforms. The standard encoding forms are: UTF-8, UTF-16 & UTF-32, with 8, 16 & 32 bits respectively.

  • 16 bit standard. 
  • Universal character.
  • 2^16=65536, used to represent different character or symbol.
  • Developed by a consortia.
  • Character Encoding System
  • Unicode is a superset of ASCII.
  • Usually, Unicode is used in internationalization and localization of computer software. This standard is also used in operating systems, XML, .NET framework and programming languages such as Java.
  • Requires more space.
ASCII vs Unicode
ASCII vs Unicode

Baudot Code

  • This is a 5 bit code used for teleprinters.
  • With 5 bits 32 combinations are possible but in this code, there are 58 symbols.
  • Hence, the same code is used for two symbols using letter shift/figure shift keys which change the meaning of a code.

Gray Code

  • The single bit change characteristic of the Gray code minimizes the chance for error.
  • The reflected binary code, also known as Gray code after Frank Gray, is a binary numeral system where two successive values differ in only one bit (binary digit).
  • The reflected binary code was originally designed to prevent spurious output from electromechanical switches.
  • Today, Gray codes are widely used to facilitate error correction in digital communications such as digital terrestrial television and some cable TV systems.

Alsan Parajuli

Hello! Viewers, He is Mr. Alsan Parajuli. He is a WordPress enthusiast, a hardworking and highly positive person. He always believes in practicality rather than theoretical knowledge. He managed to learn everything on his own, with his curiosity and fast learning skills. Despite of being from a non-IT background he loves coding, editing, writing and rummaging around Internet. He is passionate about digital marketing, website designing, and reviewing. Recently he is working as a Computer Operator in Department of National ID and Civil Registration. Moreover, he has been contributing to WordPress Biratnagar as an active member since 2018.

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We try our best to cover as many aspects of every topic making it a complete platform to prepare for your Computer Operator exams. The multiple-choice questions sets are presented in a quiz format. You can read the question and mark the correct answer from Four given options. Once you complete attempting any sets, you can request for results that will present the score, ranking along with your selections and correct answers.

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