Computer Fundamentals PDF

Shyam Gopal Timsina Computer A computer is an electronic device which takes raw data as input, processes the data and produces meaningful information to the user. It works based on instructions provided by a software or hardware program. It is designed to execute applications and provides a variety...

Shyam Gopal Timsina Computer A computer is an electronic device which takes raw data as input, processes the data and produces meaningful information to the user. It works based on instructions provided by a software or hardware program. It is designed to execute applications and provides a variety of solutions by combining integrated hardware and software components. A computer is made up of multiple parts and components that help user to perform task. A computer has two primary categories: Hardware: Physical component of a computer system which can be touched and felt is computer hardware. For example: Mouse, monitor, keyboard etc. Software: The set of computer programs combined together to execute a specific task is software. For example: MS-office, Photoshop, Windows OS etc. A computer hardware always works with software programs for reading, interpretation and execution. The combination of computer hardware and software is called computer system. IPO cycle Computer takes input from the user using input devices, processes the data using processor, stores the data for future reference using secondary storage device and produces meaningful output using output device. The process of working principle of computer system is IPO cycle. Different devices used in computer system SmartGk : “Nepal’s 1st & No.1 Online Institute” For online Class Contact Us @ 9869995445 Buddhanagar ; Kathmandu ( Near Butwal Power Company) www.smartgkonline.com  Shyam Gopal Timsina First electronic computer The ENIAC was invented by J. Presper Eckert and John Mauchly at the University of Pennsylvania and began construction in 1943 and was completed 1946. First computer in Nepal In Nepali Computer is known as (Su-saan-khya). It all started with use of IBM 1401, a second- generation mainframe computer which was used in 1971 AD (2028 BS) census. History of Computer Device Name Inventor Date Abacus Chinese 3000 BC Napier Bone John Napier 1614 AD Slide Rule William Oughtred 1622 AD Pascaline Blaise Pascal 1642 AD Stepped Reckoner Gottfried Wilhelm Leibniz 1672 AD Jacquard Loom Joseph Jacquard 1881 Difference Engine Charles Babbage 1822 Analytical Engine Charles Babbage 1834 Ada Programming Lady Augusta Ada Lovelace 1840 Tabulating Machine Dr. Herman Hollerith 1890 Mark 1 Howard H. Aiken 1943 Atanasoff-Berry Computer John Vincent Atanasoff 1942 ENIAC John Presper Eckert and John W. 1946 Mauchly SmartGk : “Nepal’s 1st & No.1 Online Institute” For online Class Contact Us @ 9869995445 Buddhanagar ; Kathmandu ( Near Butwal Power Company) www.smartgkonline.com  Shyam Gopal Timsina UNIVAC 1 John Presper Eckert and John W. 1948 Mauchly EDVAC (electronic discrete Von Neumann 1952 variable automatic computer) EDSAC (Electronic Delay Professor Sir Maurice Wilkes 1947 Storage Automatic Calculator) Computer Generation Generation in computer terminology is a change in technology a computer is being used. Initially, the generation term was used to distinguish between varying hardware technologies. Nowadays, generation includes both hardware and software, which together make up an entire computer system. There are five computer generations known till date. Each generation has been discussed in detail along with their time period and characteristics. In the following table, approximate dates against each generation has been mentioned. SmartGk : “Nepal’s 1st & No.1 Online Institute” For online Class Contact Us @ 9869995445 Buddhanagar ; Kathmandu ( Near Butwal Power Company) www.smartgkonline.com  Shyam Gopal Timsina Characteristics of a Computer 1. Speed Computers work at a very high speed. They are much faster than humans. A computer can perform billions of calculations in a second. Units Equivalent 1 Milliseconds 1000th of a second (1/1,000 of a second) (MS) SmartGk : “Nepal’s 1st & No.1 Online Institute” For online Class Contact Us @ 9869995445 Buddhanagar ; Kathmandu ( Near Butwal Power Company) www.smartgkonline.com  Shyam Gopal Timsina 1000th of a millisecond (1/1,000,000 of a second) 1 Microsecond (μs) 1000th of a microsecond (1/1,000,000,000 of a second) 1 Nanosecond (ns) 1000th of a nanosecond (1/1,000,000,000,000 of a second) 1 Picoseconds (ps) 1000th of a picosecond (1/1,000,000,000,000,000 of a 1 Femtosecond (fs) second) 2. Storage A computer can store huge amount of data. Computers use secondary storage devices to store data for future use. Computer uses Hard-Drive to store large amount of data. We can use SSD (Solid State Drive) for faster storage and access of data. Data Storage Units Chart Unit Shortened Capacity Bit b 1 or 0 (on or off) Byte B 8 bits Kilobyte KB 1024 bytes Megabyte MB 1024 kilobytes Gigabyte GB 1024 megabytes Terabyte TB 1024 gigabytes Petabyte PB 1024 terabytes Exabyte EB 1024 petabytes SmartGk : “Nepal’s 1st & No.1 Online Institute” For online Class Contact Us @ 9869995445 Buddhanagar ; Kathmandu ( Near Butwal Power Company) www.smartgkonline.com  Shyam Gopal Timsina Zettabyte ZB 1024 exabytes Yottabyte YB 1024 zettabytes 3. Processing A computer can perform different types of tasks like addition, subtraction, multiplication and division. Computer uses CPU (Central Processing Unit) to process data. SmartGk : “Nepal’s 1st & No.1 Online Institute” For online Class Contact Us @ 9869995445 Buddhanagar ; Kathmandu ( Near Butwal Power Company) www.smartgkonline.com  Shyam Gopal Timsina What is clock speed? A computer’s processor clock speed determines how quickly the central processing unit (CPU) can retrieve and interpret instructions. This helps computer complete more tasks by getting them done faster. Clock speeds are measured in gigahertz (GHz), with a higher number equating to higher clock speed. Faster clock speeds mean that you’ll see tasks ordered from your CPU completed quicker, making your experience seamless and reducing the time you wait to with your favorite applications and programs. SmartGk : “Nepal’s 1st & No.1 Online Institute” For online Class Contact Us @ 9869995445 Buddhanagar ; Kathmandu ( Near Butwal Power Company) www.smartgkonline.com  Shyam Gopal Timsina 4. Accuracy Accuracy means the capability to process data without any errors. Computer can process large amounts of data and produce accurate results. 5. Cost Reduction Computer can reduce cost. We can do a work in less time and cost by computer. A single person, with computer, can do work of many people in an office. 6. Versatile A computer can perform different types of tasks. We can use computers in different sectors. Computers are being used in banks, medical, science and engineering fields etc. 7. Diligence A computer can perform the same task repeatedly with same level of speed and accuracy without getting tired. Components of a computer System Computer system contains the combination of hardware and software. Computer hardware is group of the all the physical components that are easily manageable. Computer software is the collection of computer programs. Computer Hardware The physical component of computer is called computer hardware. There are different types of hardware devices used in the computer system. They are: 1. Input Unit Input unit consists of input devices. Input devices are used to enter data and instructions into computer memory. Examples of input devices are Keyboard, mouse, joystick, microphone, SmartGk : “Nepal’s 1st & No.1 Online Institute” For online Class Contact Us @ 9869995445 Buddhanagar ; Kathmandu ( Near Butwal Power Company) www.smartgkonline.com  Shyam Gopal Timsina Business code reader(BCR), Optical character recognition(OCR), Magnetic Ink Character Recognition(MICR), QR(Quick Response) Scanner 2. Output Unit Output unit consists of output devices. Output devices are used to show results produced by computer after data processing. There are mainly two types of output devices. They are: a) Hard copy output device: The device which gives output in printed format is called as Hard copy output device. The output given by Hard copy output device is permanent in nature. Examples: Printer, plotter etc. Printer Printers are used to produce hard copy output. They print processing results on paper. Printers are divided into two main categories: Impact Printer Non-Impact printer Impact Printer: These printers print with striking of hammers or pins on ribbon. For example: Dot Matrix printer and daisy wheel printers are impact printers. Non-Impact Printer: These printers do not use striking mechanism for printing. They use electrostatic and laser technology. Quality and speed of these printers is better than Impact printers. For example: Laser printer and Inkjet printers are non-impact printers. b) Soft copy output device: The device which gives output temporarily with the help of monitor or speaker is called soft copy output device. Examples: Monitor, Speaker etc. Monitor Monitor is the most commonly used output device used to display results of processing. It has a TV like shape. Pictures on monitor are formed with picture elements called PIXEL. Monitor produces soft copy output. Different version of monitors are: i) CRT (Cathode Ray Tube) ii) LCD (Liquid Crystal Display) iii) LED (Light Emitting Diode) SmartGk : “Nepal’s 1st & No.1 Online Institute” For online Class Contact Us @ 9869995445 Buddhanagar ; Kathmandu ( Near Butwal Power Company) www.smartgkonline.com  Shyam Gopal Timsina Resolution Resolution is how many pixels the monitor can display at a given time. The smallest resolution Windows supports is 640x480 pixels (meaning 640 dots horizontally by 480 vertically). Better video cards and monitors are capable of much higher resolutions. Refresh Rate A refresh rate is the number of times your monitor updates with new images each second. For example, a 60 Hz refresh rate means the display updates 60 times per second. A higher refresh rate results in a smoother picture. Aspect Ratio Aspect ratio describes the ratio between the width and height of an image or screen. A The first number always refers to the width, and the second number refers to the height. If the ratio of an image is different than the ratio of your screen, you may not see the whole image. Images won’t fit properly if the screen is narrower than the image. 1:1 aspect ratio, for example, is a square. 3. Central Processing Unit Central processing unit is also called CPU or Processor. It is the brain of the computer. It performs data processing. It controls overall operations and components of the computer. 4. Memory Unit Memory unit consists of memory devices to store data. For Example: RAM, ROM are the most common example of memory. RAM RAM stands for Random Access Memory. Data in RAM can be accessed directly. That is, we can access data directly from any location of RAM in the same time. This Random Access SmartGk : “Nepal’s 1st & No.1 Online Institute” For online Class Contact Us @ 9869995445 Buddhanagar ; Kathmandu ( Near Butwal Power Company) www.smartgkonline.com  Shyam Gopal Timsina quality makes RAM a very fast memory. RAM is volatile. Data and programs in RAM are erased when computer is turned off. There are two main types of RAM. a) Dynamic Random Access Memory (DRAM) Dynamic RAM is widely used in personal computers. It is a cheaper kind of RAM. DRAM stores data in the form of an electric charge. DRAM loses electric charge with the passage of time, so DRAM needs to be refreshed frequently. Otherwise, it may lose data. Dram is recharged many times in a second. Therefore, it is slower than SRAM. Since CPU cannot access the data from DRAM while it is in the process of refreshing or recharging. b) Static Random Access Memory (SRAM) Static RAM does not need to be refreshed again and again. So processor can access data from static RAM faster than DRAM. There is no time wastage in refreshing the memory again and again. Static RAM is more expensive and faster than DRAM. Static Ram is used to build a very fast memory called CACHE (pronounces 'cash' ) memory. ROM ROM stands for Read Only Memory, because its contents can be read and used only and we cannot change or delete its contents. It is a non volatile memory. It retains its contents even after switching off the computer. Therefore, ROM does not require electricity to retain its contents. ROM is a permanent memory. The instructions in ROM are written at the time of manufacturing by the manufacturer. Types of ROM a) PROM PROM stands for Programmable Read Only Memory. Instructions can be stored in PROM only once. Then it becomes ROM and we cannot change instructions in it. Initially PROM is a blank chip. Once instructions are written on it, then it become ROM. Now we cannot change or delete the instructions. If there is any error in writing instructions then PROM chip becomes unusable. b) EPROM SmartGk : “Nepal’s 1st & No.1 Online Institute” For online Class Contact Us @ 9869995445 Buddhanagar ; Kathmandu ( Near Butwal Power Company) www.smartgkonline.com  Shyam Gopal Timsina EPROM stands for Erasable Programmable Read Only Memory. Program instructions written on EPROM can be erased and changed with the help of ultra violet rays. So if once we write instruction on this chip with errors, we can erase wrong instructions and rewrite new instructions. c) EEPROM EPROM stands for Electrically Erasable Programmable Read Only Memory. Program instructions written on EEPROM can be erased with the help of electricity and rewritten. Difference between RAM and ROM RAM ROM RAM stands for Random Access Memory ROM stands for Read Only Memory. RAM is a temporary memory. ROM is a permanent memory. RAM is a volatile memory. ROM is a nonvolatile memory. When computer is turned off, all data and When computer is turned off, all data programs are and programs are erased from RAM. retained in ROM. RAM is a Read / Write memory. Data can be read ROM is a read only memory. Data and written from ROM only can be read to RAM. and not written. The instructions and data are written (loaded) in The instructions in ROM are written at RAM the time of at execution time, when computer is working. manufacturing. SmartGk : “Nepal’s 1st & No.1 Online Institute” For online Class Contact Us @ 9869995445 Buddhanagar ; Kathmandu ( Near Butwal Power Company) www.smartgkonline.com  Shyam Gopal Timsina ROM contains the instructions that RAM is used to load data and programs currently help the computer to running. start-up and make it ready for work. RAM is much faster than ROM. ROM is slower than RAM. RAM has two main types: Static RAM and ROM has three types: PROM, Dynamic RAM EPROM and EEPROM Physically ROM chip is smaller than Physically RAM chip is larger than ROM chip. RAM chip. Cache Memory Cache memory is an extremely fast memory type that acts as a buffer between RAM and the CPU. It holds frequently requested data and instructions so that they are immediately available to the CPU when needed. Cache memory is used to reduce the average time to access data from the Main memory. Computer Registers Registers are a type of computer memory used to quickly accept, store, and transfer data and instructions that are being used immediately by the CPU. The registers used by the CPU are often termed as Processor registers. A processor register may hold an instruction, a storage address, or any data (such as bit sequence or individual characters). The computer needs processor registers for manipulating data and a register for holding a memory address. The register holding the memory location is used to calculate the address of the next instruction after the execution of the current instruction is completed. SmartGk : “Nepal’s 1st & No.1 Online Institute” For online Class Contact Us @ 9869995445 Buddhanagar ; Kathmandu ( Near Butwal Power Company) www.smartgkonline.com  Shyam Gopal Timsina 5. Storage Unit Storage unit consists of storage media. Storage media are used to store large amounts of data permanently. Examples of storage media are Hard disk, CD, DVD and Zip disk etc. Types of Computer a) On the basis of working principle 1) Analog Computer 2) Digital Computer 3) Hybrid Computer 1. Analog Computer Analog computer is used to measure continuous values. It measures a physical value like voltage, pressure, speed, time and temperature. An analog computer takes input in analog form and gives output in analog form. Its output is usually displayed on a meter or scale. Analog computer has low memory and fewer functions. Analog computer is mainly used in the field of engineering and medicine. Examples of Analog Computers include: Thermometer, Speedometer, Analog clock etc. 2. Digital Computers SmartGk : “Nepal’s 1st & No.1 Online Institute” For online Class Contact Us @ 9869995445 Buddhanagar ; Kathmandu ( Near Butwal Power Company) www.smartgkonline.com  Shyam Gopal Timsina A digital computer works with digital data. Digital computer uses binary number system. Binary number system consists of only two digits 0 and 1. A digital computer represents data in digital signals. A 0 represents OFF and a 1 represents ON. Digital computers are very fast. They have large Memory. Today most of the computers used in offices and homes are Digital computers. Examples: Personal Computer, Digital Score board, Digital watch 3. Hybrid Computers A hybrid computer is a combination of both analog and digital computer. Hybrid computer can handle both analog and digital data. A hybrid computer combines the best characteristics of both the analog and digital computer. It can accept data in both analog and digital form. Hybrid computer devices are used in hospitals that may calculate patient's heart function, temperature and blood pressure etc. This calculation may be converted into numbers and shown in digital form. For example: CT Scan Machine b) on the basis of size, speed and price 1) Super Computer 2) Mainframe Computer 3) Mini Computer 4) Microcomputer or Personal Computer 1) Super Computer Super computers were introduced in 1980s. Super computer is the fastest computer. Super computer is the biggest in size and the most expensive in price than any other computers. It is the most sophisticated, complex and advanced computer. It has a very large storage capacity. It can process trillions of instructions in one second. Super Computer is the fastest and most powerful computer of a time. Supercomputers are very expensive. Supercomputers are used for highly calculation-intensive tasks. Super computers are used for specialized applications that require immense amounts of mathematical calculations. Supercomputers were designed primarily by computer scientist - Seymour Cray at Control Data Corporation (CDC). Examples: Titan IBM Sequoia, K Computer, Tianhe-I SmartGk : “Nepal’s 1st & No.1 Online Institute” For online Class Contact Us @ 9869995445 Buddhanagar ; Kathmandu ( Near Butwal Power Company) www.smartgkonline.com  Shyam Gopal Timsina Uses of Super Computer include: 1. Weather forecasting, 2. animated graphics like in Hollywood movies, 3. fluid dynamic calculations, 4. nuclear energy research, 5. space science 6. Weapon and missile design 2) Mainframe Computers Mainframe computers were introduced in 1975. A mainframe computer is a very large computer in size. It is more powerful than mini computer. It consists of multiple processors. It is designed to perform multiple tasks for multiple users at the same time. Mainframe computers can serve up to 50,000 users at the same time. The users access a mainframe computer through terminal or personal computer. A typical mainframe computer can execute 16 million instructions per second. Examples of mainframe computers are NEC 610 DEC 10 Uses of Mainframe Computers Mainframe computers are used in large organizations. For example, airlines use these computers for ticket reservation system. NADRA - The Computerized National Idenity Card Issuer in Pakistan - uses mainframe computers to maintain the information of population. 3) Mini Computers Mini computers were introduced in the 1960s. Mini Computer is larger and more powerful computer than personal computer. It can execute five million instructions per second. It generally consists of two or more processors. Mini computer can serve up to 4000 connected users simultaneously. It is normally accessed by users via personal computer or terminal. A device with a monitor and keyboard is called terminal. It is also known as dumb terminal. It has no processing power and cannot work as stand-alone computer. Examples of mini computers are: VAX-8800 AS 400. Uses of Mini Computers Mini computers are often used by small and medium-sized companies to provide centralized store of information. 4. Micro Computers Micro computer is also called personal computer. It was introduced in 1970. It contains input devices, output device, storage device, memory and processor. It is used by one person at a time. SmartGk : “Nepal’s 1st & No.1 Online Institute” For online Class Contact Us @ 9869995445 Buddhanagar ; Kathmandu ( Near Butwal Power Company) www.smartgkonline.com  Shyam Gopal Timsina Examples of personal computers are PC and Apple Macintosh. The major types of personal computers are desktop computer and portable computer. Desktop Computers These computers can easily fit on a table or desktop, hence the name. These computers come in two models or casings. In Desktop model, the system unit is placed on the desktop or table. Monitor is placed on the system unit. In Tower model, both monitor and system unit are placed on the table. Portable Computer Portable is a personal computer that can be carried from one place to other easily. Notebook computer and handheld computer (smart phone) are examples of portable computers. Notebook computer is also called laptop computer. Laptop computers are very small in size and can be placed easily on lap. Hand held computer Handheld Computers (like smart phone) are also portable. Handheld computer is also known as palmtop computer. It easily fits in the hand of the user. Uses of Micro Computer The PC is the most common type of computer used in the office. It is now widely used in many homes. These are also used for business and engineering application. Types of Computer (On the basis of Brand & Model) Types of Computer(On the basis of Brand): There are three types (brand) computers that are given below: IBM PC IBM Compatibles Apple Macintosh IBM PC : The computers that are manufactured by IBM are IBM PC. The full form of IBM is International Business Machine is one of the leading companies of the world manufacturing computers. It was established in 1924 and started manufacturing mainframe, mini and micro computer in 1945 on wards. SmartGk : “Nepal’s 1st & No.1 Online Institute” For online Class Contact Us @ 9869995445 Buddhanagar ; Kathmandu ( Near Butwal Power Company) www.smartgkonline.com  Shyam Gopal Timsina IBM Compatibles: The computers that are manufactured by other computer manufacturing companies but having the same technology and features are known as IBM Compatibles. Examples are AST, ALR, Sherry, etc. Apple Macintosh : The computers that are manufactured by Apple Company but having different architecture and configuration than IBM Compatibles are known as Apple Macintosh. Apple Company was established in late 1970s and giving a good competition to IBM company. Types ( Model) There are three types (model) of computer that are as follows: XT Computers (Extended Technology) AT Computers (Advanced Technology) PS/2 Computers (Personal System 2) XT Computers : The computers having 8086 or 8088 microprocessor and processing speed of 4.77 Mhz are known as XT Computers. These computers are outdated now because they cannot run on latest software versions. AT Computers : The computers having 80286 or later versions of microprocessors are known as AT Computers. Their storage capacity as well as speed is much higher than XT computers. Besides that they have math co-processor to support main processors to perform complex mathematical calculations. PS/2 Computers: IBM developed another model of computer in 1990 that have much advanced architecture design that AT computers. They are known as PS/2 computers. They are much faster than AT computers. Most of the laptop computers based on PS/2 model use OS/2 or UNIX operating system and 1.44 MB floppy diskette. SmartGk : “Nepal’s 1st & No.1 Online Institute” For online Class Contact Us @ 9869995445 Buddhanagar ; Kathmandu ( Near Butwal Power Company) www.smartgkonline.com  Shyam Gopal Timsina Importance of ROM 1. One important reason a computer needs ROM is that instructions stored in ROM (called ROM BIOS - Basic Input/Output System) execute on start-up of computer and guide the computer what to do. They make the computer ready for work. 2. ROM contains a set of start-up instructions to check that memory is functioning well and check for other hardware devices. 3. These instructions also check for an operating system and load its necessary part into RAM, so that a user interface for example "Windows Desktop" is displayed on computer screen. Now computer is ready to work with. A user now can easily perform work on computer. Storage Devices Storage devices are used to store data and instructions permanently. Storage devices are also called secondary storage devices / backing storage devices / external storage devices or auxiliary storage devices. Examples of storage devices include Hard Disk, CD and DVD etc. Why Secondary Storage Devices are Used? 1. Primary memory(RAM) is volatile and temporary. When computer is switched off, all data in ram is erased. 2. Storage devices can store large amounts of data and instructions permanently whereas Primary memory has less capacity of storing data. Types of Storage Devices There are three main types of storage devices: 1. Magnetic Tape 2. Magnetic Disk 3. Optical Disk SmartGk : “Nepal’s 1st & No.1 Online Institute” For online Class Contact Us @ 9869995445 Buddhanagar ; Kathmandu ( Near Butwal Power Company) www.smartgkonline.com  Shyam Gopal Timsina 1. Magnetic Tape Magnetic tape is the oldest storage device. It is made of plastic coated with magnetic material. Data is stored on magnetic tape in the form of magnetic spots. Tape drive is used to read and write data on tape. Magnetic disk is sequential access device. It is slower device than magnetic disk or optical disk. Magnetic tapes are used in reels of different lengths, for example 200, 600, 1200 feet etc. 2. Magnetic Disk A magnetic disk is a thin circular metal or plastic disk coated with magnetic material. Data is stored in the form of magnetic spots. Magnetic disk is random access device. It is faster than magnetic tape. There are three main types of magnetic disk: a. Hard Disk b. Floppy Disk c. Zip Disk a. Hard Disk The hard disk is also called fixed disk. It consists of one or more metal plates. The plates are fixed in the drive. Metal plates are coated with magnetic material to store data. A motor rotates disks. There is also an access arm and read / write heads to read and write data on disks. Following are major characteristics of hard disk: - The storage capacity of hard disk is much greater than floppy disk. - Nowadays hard disks of size 1TB is also available. b. Floppy Disk Floppy disk is a small plastic plate coated with magnetic material. Data is stored in magnetic spots. Main advantage of floppy disk is that it is used to transfer data from one computer to another. Floppy disk drive is used to read and write data on floppy disk. c. Zip Disk Zip disk is similar to 3 ½ inch floppy disk. But it can store 100 MB or more data. Zip disk drive is used to read and write data on a zip disk. SmartGk : “Nepal’s 1st & No.1 Online Institute” For online Class Contact Us @ 9869995445 Buddhanagar ; Kathmandu ( Near Butwal Power Company) www.smartgkonline.com  Shyam Gopal Timsina 3. Optical Disk LASER technology is used to read and write data on Optical disk. LASER stands for Light Amplification through Emission of Radiation. Laser beam writes on the surface of optical disk by creating very small holes. The presence of hole represents a One and absence of the hole represents a Zero. There are following main types of optical disk. 1.CD-ROM 2. CD-R or WORM 3. CD-RW 4.DVD-ROM, 5. DVD-R, 6. DVD-RW 1. CD-ROM CD-ROM stands for Compact Disk-Read Only Memory. The data stored on Cd-Rom can only be read. It cannot be deleted or changed. It is a portable storage device. Data can be easily transferred by CD Rom from one computer to another. Commonly it can store 650 MB / 700 MB/ 750 MB data. It is used to store large amounts of data like Software or audio/video data.We purchase Software, movies, dramas, lectures, books, wallpapers and other data on Cd-Rom. There are many Advantages of Compact Disk. 2. CD-R (CD Recordable) Or WORM (Write Once Read Many) CD-R stands for Compact Disk -Recordable. Initially, it is a blank disk. User can store data on it only once. This is why it is also called WORM(Write Once Read Many) disk too. Because we can write data on it only once and later we can read many times. The devices to store data on CD-R are called CD Writers or CD Burners. We can write data on CD-R only once, but can read data many times. Because of this write once read many quality, CD-R is often known as WORM(write once read many). 3. CD-RW ( CD Rewritable ) CD-RW stands for Compact Disk Rewritable. This is a special type of CD. User can write data on it, if there is an error in writing data, he may erase the contents and rewrite again. CD-Writers are used to store data on CD-RW. SmartGk : “Nepal’s 1st & No.1 Online Institute” For online Class Contact Us @ 9869995445 Buddhanagar ; Kathmandu ( Near Butwal Power Company) www.smartgkonline.com  Shyam Gopal Timsina 4. DVD - Digital Video Disk (DVD-ROM) DVD stands for Digital Video Disk. A laser beam with a short wave length is used to create very very small holes on the surface of disk. So there are much more tiny holes on the surface of DVD as compared to that of CD. Therefore, storage capacity of DVD is much larger than CD. It can store up to 17 GB or more data. DVD-ROM is pre recorded and it can contain data like movies, videos and software etc. User cannot change or delete data from DVD-ROM. It is read only. There are several Benefits of using Digital Video Disk or DVD. 5. DVD-R (DVD-Recordable) DVD-R stands for Digital Video Disk Recordable. Initially it is a blank disk. User can store data on disk only once. Then it becomes read only. It is normally used to store high definition video movies. DVD-Writers are used to store data on DVD-R. 6. DVD-RW (DVD Rewritable) DVD-RW stands for Digital Video Disk Rewritable. User can write data on disk many times by erasing the old data. 7. Blu-Ray Disk Blu-Ray Disk is an optical disk used to store digital information such as high-definition video, and able to store more information than a standard DVD Blu-ray Disk pronounced as Blue-ray Disk is the name of a new type of optical disc format. The format offers more than five times the storage capacity of traditional DVDs. A Blu Ray disk can hold up to 25GB on a single-layer disc and 50GB on a dual-layer disc. Moreover an other difference between DVD and Blu-Ray disk is that current optical disc technologies such as DVDs rely on a red laser to read and write data, whereas the new format ( Blu-Ray disk) uses a blue-violet laser instead, hence the name Blu-ray Disk. Software Software is a set of instructions that tell a computer what to do. Software is the set of instructions given to computer to perform a task or to control operations of computer. Software cannot be touched. There are different types of software used in computer system. The hardware cannot SmartGk : “Nepal’s 1st & No.1 Online Institute” For online Class Contact Us @ 9869995445 Buddhanagar ; Kathmandu ( Near Butwal Power Company) www.smartgkonline.com  Shyam Gopal Timsina perform any task without software. Software is installed on computer system. When we use any software it is loaded into computer’s memory. Types of Software The main types of software are system software and application software. 1. System Software System software is a set of programs used to implement certain functions in a computer system. System software controls the overall operations and components of a computer system. We can say that system software is the base on which application programs are executed. System software provides an interface between user and computer. Users use this interface to interact with the computer and perform different jobs on computer. Operating systems like Windows, Linux and Unix are the main example of system software. Similarly device drivers are also examples of system software. Examples of system software are as follows: SmartGk : “Nepal’s 1st & No.1 Online Institute” For online Class Contact Us @ 9869995445 Buddhanagar ; Kathmandu ( Near Butwal Power Company) www.smartgkonline.com  Shyam Gopal Timsina Operating System Operating system is software to control overall operations and components of a computer system. e.g., Windows, UNIX, Linux and Dos etc. Utility Programs Utility program is used to solve a particular problem of software or hardware, for example, Antivirus program, disk scanner and File Viewer etc. Device Drivers Device driver is software that permits a computer system to communicate with a device. e.g., device driver software for a printer comes with it on CD. We have to install device driver before using a device. Language Processor Language processor is software that converts a source program into object program. For example C- compiler converts a program written in C language into object (machine code). Other examples are assembler, compiler etc. 2. Application Software Application software is a program needed to perform various applications on the computer by the user. It helps a computer user to solve specific problems like to prepare letters and other documents, to create pictures and advertisements, to perform large calculations quickly etc.The application software runs on top of the operating system software. Examples of application software are Word Processing, Spreadsheets, Database etc. There are two types of application software. They are: 1. Packaged software is a collection of programs that perform similar functions or have similar features. For example, Microsoft Office includes multiple applications such as Excel, Word, and PowerPoint. Video and audio editing software may also be SmartGk : “Nepal’s 1st & No.1 Online Institute” For online Class Contact Us @ 9869995445 Buddhanagar ; Kathmandu ( Near Butwal Power Company) www.smartgkonline.com  Shyam Gopal Timsina available as packaged software, used for editing music and video files used in a movie. 2. Tailored/Customized software is made for an individual or business that performs tasks specific to their needs is called customized software. For example, software used for result processing in school, college etc. Programming Language Programming language is the platform to write computer programs. Thus, programming language is the medium of communication between you (a person) and a computer system. It is the set of some instructions written in a specific style (coding) to instruct the computer to do some specific task. Types of computer programming languages There are two types of computer programming languages, they are 1. Low level programming language 2. High level programming language 1) Low level programming language There are mainly two types of low-level programming language. They are: a) Assembly Language Assembly language uses mnemonics to write program codes. It needs to be converted in equivalent Binary code. So, computer cannot understand the instructions written in Assembly language directly. Assembler is used to convert an assembly code to its equivalent Binary code. b) Machine Language Machine language is machine dependent programming language. Since computer only understand the Binary language that means instructions in the form of 0’s and 1’s, so machine language is the best way to give signals (Binary Instructions) to the computer directly. Machine Code (Binary Language) does not need any interpreter or compiler to convert language in any SmartGk : “Nepal’s 1st & No.1 Online Institute” For online Class Contact Us @ 9869995445 Buddhanagar ; Kathmandu ( Near Butwal Power Company) www.smartgkonline.com  Shyam Gopal Timsina form because computer understands these signals directly. It is the mother tongue of computer. The codes written in such kind of languages are difficult to write, read, edit and understand the programs are not portable to any other computer system. 2) High level programming language These are the machine independent programming languages, which are easy to write, read, edit and understand. The languages like Java,.Net, Pascal, Python, COBOL, C++, C, C# are very popular now to develop user end applications. These languages come under the high-level programming language category. High level programming languages have some special keywords, functions and class libraries by using them we can easily build a program for the computer. Computer does not understand program written in such languages directly so, language translators are required to convert a high-level program to its equivalent Machine code. Language translators such as Compilers and Interpreters are the system software’s which converts a program written in particular programming languages to its equivalent Machine code. Firmware Firmware is a software program permanently attached into a hardware device such as a keyboards, hard drive, BIOS, or video card. It is programmed to give permanent instructions to communicate with other devices and perform functions like basic input/output tasks. Firmware is typically stored in the flash ROM (read only memory) of a hardware device. It can be erased and rewritten. Firmware was originally designed for high level software and could be changed without having to exchange the hardware for a newer device. Firmware also retains the basic instructions for hardware devices that make them operative. Without firmware, a hardware device would be non- functional. SmartGk : “Nepal’s 1st & No.1 Online Institute” For online Class Contact Us @ 9869995445 Buddhanagar ; Kathmandu ( Near Butwal Power Company) www.smartgkonline.com