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INTRODUCTION TO COMPUTERS

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Published in: Basic Computer
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Computer, Characteristics  Computer System  Types of Memories  Types of Input/Output devices  Processor  Graphical User Interface (GUI)  S/w & H/w  Network, Types of Networks

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  1. Unit 1 Introduct ion to computers Computer, Characteristics Computer System Types of Memories Types of Input/Output devices Processor Graphical User Interface (GUI) s/w & H/w Network, Types of Networks Introduction: Introduction to computers Quick view Note: Italic questions are most important. Computers are termed as 'Man of the Year' in a magazine recently. The term computer is derived from a latin word 'computare' meaning 'to compute' (to calculate). • A computer is an electronic machine, devised for performing calculations and controlling operations that can be expressed either in logical or numerical terms. In simple terms, computer is an electronic device which accepts the input (Data) from the user, processes it and produces the output (Information). Explain the Character istics of Computers? The human race developed computers so that it could perform intricate operations, such as calculation and data processing, or simply for entertainment. Today, much of the world's infrastructure runs on computers and it has profoundly changed our lives, mostly for the better. Let us discuss some of the characteristics of computers, which make them an essential part of every emerging technology and such a desirable tool in human development. Speed: The computer process data at an extremely fast rate, at millions or billions of instructions per second. A computer can perform a huge task in a few seconds that otherwise a normal human being may take days or even years to complete. The speed of a computer is calculated in MHz (Megahertz), that is, one million instructions per second. At present, a powerful computer can perform billions of operations in just one second. Accuracy: Besides the efficiency, the computers are also very accurate. The level of accuracy depends on the instructions and the type of machines being used. Since the computer is capable of doing only what it is instructed to do, faulty instructions for data processing may lead to faulty results. This is known as GIGO (Garbage In Garbage Out) Diligence: Computer, being a machine, does not suffer from the human traits of tiredness and lack of concentration. If four million calculations have to be performed, then the computer will perform the last, four-millionth calculation with the same accuracy and speed as the first calculation. 1
  2. Unit 1 Introduction to computers Reliability: Generally, reliability is the measurement of the performance of a computer, which is measured against some predetermined standard for operation without any failure. The major reasons behind the reliability of computers are that, at hardware level, it does not require any human intervention between its processing operations. Moreover, computers have built-in diagnostic capabilities, which help in continuous monitoring of the system. Storage Capability: Computers can store large amounts of data and can recall the required information almost instantaneously. The main memory of the computer is relatively small and it can hold only a certain amount of data, therefore, the data is stored on secondary storage devices such as magnetic tape or disks. Small sections of data can be accessed very quickly from these storage devices and brought into the main memory, as and when required, for processing. Versatility: Computers are quite versatile in nature. It can perform multiple task simultaneously with equal ease. For example, at one moment it can be used to draft a letter, another moment it can be used to play music and in between, one can print a document as well. All this work is possible by changing the program (computer instructions) Resource Sharing: In the initial stages of development, computers used to be isolated machines. With the tremendous growth in computer technologies, computers today have the capability to connect with each other. • This has made the sharing of costly resources like printers possible. Apart from device sharing, data and information can also be shared among groups of computers, thus creating a large information and knowledge base. LIMITATIONS OF A COMPUTER: A computer can only perform what it is programmed to do. The computer needs well-defined instructions to perform any operation. Hence, computers are unable to give any conclusion without going through intermediate steps. A computer's use is limited in areas where qualitative considerations are important. For instance, it can make plans based on situations and information but it cannot foresee whether they will succeed. Explain the types of storage devices? There are two types of storage devices used in computers — a 'primary storage' device and a 'secondary storage' device. (A). PRIMARY OR MAIN MEMORY: A storage location that holds memory for short periods of times. RAM and ROM are examples of a primary storage device. This storage unit is often called either 'main memory' or 'primary memory'. The primary memory of CPU is the place where compute program and data is stored during processing. RANDOM ACCESS MEMORY (RAM): Pronounced ram acronym of Random Access Memory, a type of computer-memory that can be accessed randomly; that is, any byte of memory can accessed without touching the preceding bytes. This is the memory that the computer uses while it is executing programs. RAM is the most common type of memory found in computers and other devices, such as printers. liiiiiiiitdftt
  3. Unit 1 Introduction to computers There are two basic types of RAM: Dynamic RAM (DRAM), Static RAM (SRAM). • Dynamic RAM needs to be refreshed thousands of time per second. • Static RAM needs to be refreshed less often, which makes it faster but it is also more expensive than dynamic RAM. Both types of RAM are volatile, meaning that they lose their contents when the power is turned off. READ ONLY MEMORY (ROM): Pronounced rom, acronym for Read-Only Memory, a computer memory on which has been prerecorded. The information stored on the ROM, chips is permanent and is stored when it's manufactured. • Unlike the main memory (RAM), ROM retains its contents even when the computer is turned off. ROM is referred to as being nonvolatile whereas RAM is volatile. Used at: • Most personal computers contain a small amount of Rom that stores critic programs such as the program that boots the computer. ' ROMs are used extensively in calculators and peripheral devices such as laser printers, whose fonts are often stored in ROMs. PROM: Pronounced prom, an acronym for programmable read-only memory. PROMs are manufactured as blank chips on which data can be written. A PROM is a memory chip on which data can be written only once. Once a program has been written onto a PROM, it remains there forever. • Unlike the main memory, PROMs retain the contents when the computer is turned off. • The difference between a PROM and a ROM (read-only memory) is that PROM is manufactured as blank memory, whereas a ROM is programmed during the manufacturing process. • To write data onto a PROM chip you need a special device called a PROM programmer or a PROM burner. The process of programming a PROM is sometimes called burning the PROM. EPROM: Acronym for Erasable Programmable Read-Only Memory and pronounced eeprom. EPROM is a special type of memory that retains its contents until it is exposed to ultraviolet light. The ultraviolet light clears its contents, making it possible to reprogram the memory. EEPROM: Acronym for eclectically Erasable Programmable Read-Only Memory. Pronounced double ee- prom • An EEPROM is a special type of PROM that can be erased by exposing it to an electrical charge. Like other types of PROM, EEPROM retains its contents even when the power is turned off. Also like all other types of ROM, EEPROM is not as fast as RAM. VIRTUAL MEMORY: Because computer has a finite amount of RAM, it is possible to run out of memory when too many programs are running at one time. This is where virtual memory comes in. Virtual memory increases the available memory of computer by enlarging the "address space", or places in allocation. CPU CACHE MEMORY RAM VIRTUAL MEMORY memory where data can be stored. It does this by using hard disk space for additional memory 3
  4. Unit 1 Introduction to computers The area of the hard disk that stores the RAM image is called a page file. It holds pages of RAM on the hard disk, and the operating system moves data back and forth between the page file and RAM. When the operating system has to constantly swap information back and forth between RAM and the hard disk. This is called thrashing, which can make the computer incredibly slow. This means that the more virtual memory is used, the more it will slow the computer down. While virtual memory enables the computer to run more programs than it could otherwise, it is best to have as much physical memory as possible. Cache memory: A special temporary memory assigned with a processor, allowing the processor's speed in executing instructions. Cache memory stores the frequent instructions & data which are required to finish the job by the processor, thus saving the time of the processor instead of loading those frequent instructions & data from RAM. (B). SECONDARY STORAGE DEVICES: CPU CACHE MEMORY RAM A storage medium that holds information until it is deleted or overwritten. The memory capacity of the computer can be increased by using secondary or external or auxiliary memory units to the computer. MAGNETIC TAPE: They are convenient, inexpensive devices which can be used to store large volumes of data. The magnetic tape is similar to the commonly used audio tape recorders. The tape is wound on a spool and threaded manually on the take-up spool. Data on tapes is stored as blocks, therefore recording and retrieving is sequential. The access time in the cases of magnetic tapes is quite high. MAGNETIC DISKS: A magnetic disk is a circular platter that is made of smooth metal or mylar plastic. It is coated with magnetic material. • Data is stored or retrieved from the disk using a conducting coil called the head. ' During read/write the head is stationary while the platter rotates beneath it. A : Track B : Geometrical Sector C: Track Sector D: Cluster • With disks it is possible to directly access records by specifying the address or location. That is why disks are called direct access storage devices. FLOPPY DISK: Floppy disk is a soft magnetic disk. Unlike most hard disks, floppy disks (often called floppies or diskettes) are portable, because you can remove them from a disk drive. C 4
  5. Unit 1 Introduction to computers • Disk drives for floppy disks are called floppy drives. Floppy disks are slower to access than hard disks and have less storage capacity, but they are less expensive and portable. HARD DISK: Hard disk is a magnetic disk on which one can store computer data. The hard disk is faster than floppy than floppy disks. For example, hard disk can store anywhere from one megabytes to several gigabytes, whereas most floppies have a maximum storage capacity of 1.4 megabytes. • A single hard disk usually consists of several platters. Each platter requires two read/write heads, one of each side. In general, these are less portable than floppies, although it is possible to buy removable hard disks. FLASH DRIVE: A USB flash drive consists of a flash memory data storage device integrated with a USB interface. USB flash drives are typically removable and rewritable, and much smaller than a floppy disk. Most weigh less than 30g. Storage capacities can be as large as 256 GB with steady improvements in size and price per capacity expected. It is also called 'thumb drive' or 'pen drive' These is a portable memory device that can be used to quickly transfer to audio, video and data files from the hard drive of one computer to another. OPTICAL DISK: Optical disks can store much more data up to 6 gigabytes (6 billion bytes) than magnetic media, such as floppies and hard disks. Optical disk is an electronic data storage medium from which data is read and written to by using a low- powered laser beam. It is flat, circular, plastic or glass disk on which data is stored in the form of light and dark pits. The laser beam reads the pits and the data can accessed. Optical disks differ from magnetic disks by the way data is stored and read. In optical disks a laser beam is used to read and write data on these reflective disks. Optical disks support direct access to data and have more storage capacity than magnetic disks. Optical disks are popularly known as compact disks (CDs). CD-ROM: A CD-ROM is a CD that contains computer data, which cannot be read or rewritten. In computer, CD- ROM is the most commonly used optical storage technology. CD-ROM is a compact disc that contains information, which is accessible by a computer. A laser beam reads the pits and the data can be accessed. 5
  6. Unit DVD-ROM: 1 Introduction to computers DVD-ROM is an abbreviation of Digital Versatile Disc-read only memory. DVD-ROM is an optical disc storage media format that can be used for data storage, which includes movies with high video and sound quality. A DVD is composed of several layers of plastic, totaling about 1.2 millimeters thick. Each layer is created by injection molding polycarbonate plastic. Explain the Computer System / Basic Components of a Computer? A computer can be viewed as a system, which consists of a number of interrelated components that work together with aim of converting the data into the meaningful information. Data/lnput entered through such data is Input unit, processed by CPU, & the input Unit output/result displayed through Output unit. Input Unit: It contains devices like keyboard, mouse etc...by which we enter data into CPU Unit Control & Unit Cenyponents of a corn puter computer. This unit makes link between user and computer. The input devices translate the human being information into the form understandable by computer. CPU (Central Processing Unit): CPU is considered as the brain of the computer. CPU performs all types of data processing operations. It stores data, intermediate results and instructions (program). It controls the operations of all parts of computer. CPU itself has the following three components Memory Unit Control Unit ALU (Arithmetic Logic Unit) Memory or Storage Unit: This unit can store instructions, data and intermediate results; it is also known as internal storage unit or main memory or primary storage or Random access memory (RAM). Its size affects speed, power and capability. There are primary memory and secondary memory, two types of memories in the computer. Primary memory stores all the data & instructions to be processed during the course of processing, it intermediate results of processing. These results are accessed by the C stores PU and are transferred to Output Unit. Secondary storage memory supplies the stored information to other units of the computer as and when required. All inputs and outputs are transmitted through main memory. Control Unit: This unit controls the operations of all parts of computer. It does not carry out any actual data processing operations. It is responsible for controlling the transfer of data and instructions among other units of a computer. It manages and coordinates all the units of the computer. 6
  7. Unit 1 Introduction to computers It obtains the instructions from the memory, interprets them and directs the operation of the computer. It communicates with Input/output devices for transfer of data or results from storage. It does not process or store data. ALU (Arithmetic Logic Unit): This unit consists of two subsections namely: Arithmetic Section & Logic Section ARITHMETIC SECTION: Function of Arithmetic section is to perform arithmetic operations like addition, subtraction, multiplication and division. All complex operations are done by making repetitive use of above operations. LOGIC SECTION: Function of logic section is to perform logic operations such as comparing, selecting, matching and merging of data. Registers: Registers are the special purpose, high-speed temporary storage area units within the CPU When CPU executes the instructions, there is a transfer of information between various units of the computer. CPU uses the registers to handle the process of execution effectively & efficiently. Registers receive the information, hold it temporarily & pass it on as directed by the Control Unit. Ex: If two numbers are to be multiplied, both numbers must be in registers, and the result is also placed in a register. (The register can contain the address of a memory location where data is stored rather than the actual data itself.) Output Unit: Output unit consists of devices with the help of which we get the information from computer. An output device is used to present the processed form of data (results) to the user. It receives the result in machine-coded form from the cpu, and then converts them into user understandable format such as graphics/audio/video/text etc... Output devices translate the computer's output into the form understandable by users. Explain the Input & Output devices? A computer accepts input either manually or directly. In the case of manual data entry, the user enters the data into the computer by hand, say using keyboard & mouse. A user can also enter the data directly by transferring the information from a source document into the computer (EX: Bar code reader). There are many Input & Output devices, let's have a look on most commonly used Input & Output devices. An input device is a machine that feeds data into a computer. Without input device the computer is much like a TV. Input devices help the users to interact with the computer. Parts of a Keyboard 1 Escape Key Function Keys Typewriter Keys S ace Bar ontrolKeys Extra Keys * E'3Z Cursor Keys Shift Keys Numeric Enter Key 1 1 1 1 1 1 1 1 Alt Keys Windows
  8. Unit 1 Introduction to computers Keyboard: It is the standard Input device for CUI Systems (Character User Interface). Keyboard resembles a regular typewriter with few additional keys. The layout of the keyboard keeps on changing according to the requirement; the number of keys on the keyboard varies from 84 keys to 104 keys. Portable computers such as laptops quite often have custom keyboards instead of standard keyboard arrangement. Keyboard: easy to use, less in price, difficult for people with muscular disorder. Pointing devices: Hey, Keyboard is not convenient for some applications (inputting data). For example if you want to select an item from a list, the user can identify and position those items by selecting them through keyboard. However this action would be more easily & quicker if you have any pointing device, which can quickly move on your screen from corner-corner, ease to drag the items etc. Some of the Pointing devices like mouse, trackball, joystick, pen, touch screen. Mouse: The mouse is the standard input device for GUI systems. Mouse is a small hand-held pointing device that controls the movement of the cursor (pointer) on the screen. There are 2 types of mouse, Mechanical & Optical mouse. ' Mechanical mouse uses a rubber ball at the bottom surface, which rotates as the mouse is moved over a flat surface. • An optical mouse uses a light beam instead of rotating ball. Mouse allows us to create graphic elements on the screen such as lines, curves etc... so it is very important for GUI (Graphical User Interface). Hey, the function of the work depends on what the application you're running. Trackball: Trackball is another pointing device that serves as an alternate to mouse. Trackball is a mouse which is turned upside down. It has a ball inside a square cradle. To move the pointer, you rotate the ball with your fingers/thumb instead of moving the entire arm, the user can get more precision and accuracy, so the designers interested in using it. It takes less space. Joystick: Joysticks are mostly used in games, flight simulators, training simulators, CAD/CAM systems & for controlling industrial robots; they allow the movements in all directions up to 360 . Joystick - A lever that moves in all directions and controls the movement of the cursor • A joystick is similar to mouse except that with a mouse the pointer stops moving as soon as you stop moving the mouse. With a joystick, the pointer continues moving in the direction the joystick is pointing to. To stop the pointer, one must return the joystick to its upright position. 8
  9. Unit Light Pen: 1 Introduction to computers An input device that utilizes a light-sensitive detector to select objects on a display screen. A light pen is similar to a mouse, except that with a light pen you can move the pointer and select objects on the display screen by directly pointing to the objects with the pen Touch screen: The display has a touch sensitive transparent panel covering the screen. It is a special kind of input device allows the user to select the desired menu item or icon with the touch of a finger. It is not useful to input large amounts of data. - - - -- - hey pointing devices ends here- - -- - - Digital Camera: stores images in the form of digital files rather than recording them on a film. Take the picture, transfer to the computer, if required - make the changes by the help of software and get printed. Best quality, Speed & in-expensive. Microphone: A speech recognition program converts the audio input to machine recognized commands. It is abbreviated as 'mic' a hardware peripheral invented by Emile Berliner in 1877. Scanners: A scanner is an input device that converts a document into an electronic format that can be stored on your disk, that electronic image can be edited, manipulated, combined, and printed by using the image editing software. Scanners also called Optical scanners as they use a light beam to scan the input data. Hand-held scanner It consists of emitting diodes, placed over the document to be scanned. It performs scanning slowly with its light from top to bottom, finally the document converts & stored as an image. It is used where much accuracy is not important. Size is small, available in different resolutions. These devices read the data on price tags, shipping labels, inventory part number, book ISBN etc... Flat-bed scanner It looks similar to photocopier machine. It consists of a box containing a glass plate on its top and a lid that covers the glass plate, this glass plate is used to place the document to be scanned. Light beam is placed below the glass plate, moves left-right when it gets activated. Scans line by line, Scanning A4 size paper takes 20 seconds. 9
  10. Unit Help 1 Introduction to computers Larger in size-More expensive as it produces better quality image. OMR (Optical Mark Reader): Optical Mark Recognition is the process of detecting the presence of intended marked responses. Optical mark reading is done by a special device OMR; it is commonly used to find the scoring in tests. It can read 2,000 documents per hour. It can also be used for applications such as order writing, payroll, questionnaires etc MICR (Magnetic Ink Character Reader): You must have seen special magnetic encoding characters printed on the bottom of a cheque, Those characters are printed using special ink, which contains iron particles that can be magnetized. To recognize these magnetic ink characters, MICR is used. It reads the characters by examining the shape of characters in matrix form. Very efficient — Time saving for data processing InvestmentKit.com PAY RUPEES 'CW DELHI • RTGStNEFT IFS : PUNBOOt4700 CURRENT PAYAmE AT ALL BRANCHES IFSC Code OAT oh OR BEARER 9 Digit MICR Code ••q 20580" "00 Barcode reader: Bar-Code is a machine readable code in the form of a pattern of parallel vertical lines of varying widths. You can see the bar code on goods in super market etc... this code is read by a Bar Code Reader using reflective light. This reader fed the code to the computer, which recognizes the info from thickness, spacing, numbers etc. Super markets use a bar code system called Universal Product Key (UPC). Output is the data that has been processed into useful information. It can be displayed or viewed on a monitor, printed on a printer, or listened through speakers/headset. The output, which can be easily understand by human beings are Soft Copy & Hard Copy. Soft copy output is displayed on screen, is temporary, and cannot be touched; It includes Audio &/Video/Text/lmage. Hard copy is the physical form of output. It is the information copied from computer onto paper or some other durable surfaces. It is permanent & physical. 10
  11. Unit Printers: 1 Introduction to computers A printer prints information & data from the computer onto a paper. Generally, the printer prints 80 or 132 columns of characters in each line & prints either on single sheets, or on a continuous roll of paper. The quality of the print is determined by the Resolution, higher resolution, the better print. For printers resolution is measured in dpi (number of dots per inch); more dots, more quality. Ex: 600 dpi printers can print 360,000 dots per square inch. (Resolution is used to describe the sharpness & clarity of image) Printers are classified into 2 categories: Impact & Non-Impact printers. Impact printers • Impact printers: work by physically striking a head or needle against an ink ribbon to make a mark on the paper. Ex: Dot matrix printer, Daisy wheel printer, Drum printer etc... They can produce multiple copies at a time. Dot matrix printer (Wire matrix printer): Uses oldest printing technology; Prints one character at a time. Speed of Dot matrix printer is measured in characters per second (CPS: 200 to 500 in-general) The print quality depends on the number of pins it has (vary from 9 to 24) Non-impact Printers In contrast to Impact printers, Non- Impact printers use the techniques other than physical striking the page to transfer ink onto the page. Ex: Ink-jet printers, Laser printers etc... They cannot produce multiple copies as there is no mechanical force to produce output on the paper. More pins per inch = More resolution = More quality output. (Resolution vary from 72-360 dpi) Inexpensive, you can print in different types of fonts Only prints in Black & White. It is commonly used for low-quality applications. Daisy wheel printer (Letter quality printers/Smart printers): Dot matrix prints are unprofessional in look, if you're looking for professional letter quality documents Daisy wheel printer is the best option. Prints slow when compared with dot matrix, more expensive but produces better quality prints. Produce high resolution; Printing speed up to 90 cps. Daisy is named to this printer because the print head of this printer resembles a daisy flower, with printing arms that appear like petals of the flower. 11
  12. Unit 1 Introduction to computers Internal Working: Daisy wheel printer has a wheel with a number of spokes made up of metal and plastic, each spoke carries a typeface at the lower end; the wheel rotates until the appropriate character comes under the hammer, which strikes to produce the impression on the paper. Wheels are inexpensive & removable, if you want to change the font style you've to replace the wheel. Drum printer: It is a line printer = it prints one line of characters at a time. It has a drum that rotates at high speed Printing speed: 300-2000 lines per minute with 96-160 characters on a 15-inch line Commonly used for heavy printing applications Expensive & character fonts cannot be changed. Ink-jet printers: Can print 6 pages per minute It is a non-impact printer, most common type of printer found in homes today Ink-jet printer has a series of nozzles to spray drops of ink directly onto the paper Able to print in the combination of CMYK colours (Cyan, Magenta, Yellow & Black) High quality prints, graphics & text &/special characters even with different sizes. Resolution = 600 dpi or moree Laser Printers: Ham me-s Cone far RI b bon indrie.* I Arum with cfizracters Tot-al ru.rr-bqr af is tha Tia * irruw-n number of characters (print goslt ons) on a llne Fly. 5.1 r Prlntlnø Machanlsm of a Drum Prlnter Actuator current ca using to vbrate Ink pushed—— out the rna nåold v b rates Ink drop only - Actual size not Plotter: These are non-impact page printers. They use laser lights to produce the dots needed to form the characters to be printed on a page. Advantages: Very high speed - Very high quality output - Gives good graphics quality - Supports many fonts and different character sizes. Disadvantages: Expensive - Cannot be used to produce multiple copies of a document in a single printing A plotter is a pen-based output device that is attached to a computer for making vector graphics, i.e., images created by a series of many straight lines. Used to draw high-resolution charts, graphs, blueprints, maps, circuit diagrams Used in CAD, CAM, AUTOCAD etc... (CAD-Computer aided design; CAM=Computer aided Manufacturing) 12
  13. Unit 1 Introduction to computers Monitor: The monitor is the most frequently used output for producing soft-copy output. A monitor is a TV like display attached to the computer on which the output is viewed. They available in different sizes (14-21 inches & more) CRT Monitors: Computer monitors uses CRT technology (Cathode Ray Tube) A Beam of electrons (cathode rays) emitted by the electron gun falls on the phosphor-coated screen, in a short period (10-60 microseconds) image will be appeared on the monitor Most screens are capable of displaying 80 characters of data horizontally and 25 lines vertically. Disadvantages of CRT: Large in Size, High power consumption Flat-Panel Display Monitor: The flat-panel display refers to a class of video devices that have reduced volume, weight and power requirement compared to the CRT. You can hang them on walls or wear them on your wrists. Current uses for flat-panel displays include calculators, video games, monitors, laptop computer, graphics display. The flat-panel display are divided into two categories: O LCD Monitors: Emissive Displays - The emissive displays are devices that convert electrical energy into light. Ex: Plasma panel and LED (Light-Emitting Diodes). Non-Emissive Displays - Use optical effects to convert sunlight or light from some other source into graphics patterns. Ex: LCD (Liquid-Crystal Device) With the widespread use of smaller computers like PDAs & laptops, a new display technology LCD (Liquid Crystal Diode) has made its impact on computer market. The main advantage of LCD displays is that they take up less desk space and are lighter. Currently, however, they are also much more expensive. LCD displays utilize two sheets of polarizing material with a liquid crystal solution between them. An electric current passed through the liquid causes the crystals to align so that light cannot pass through them. Each crystal, Liquid Crystal. Voltage Polarizer Color fitter Color filter glas Polarizer Backlight therefore, is like a shutter, either allowing light to pass through or blocking the light. LCD belongs to Flat-Panel display, other Flat-Panel displays include Electro Luminescent (EL) display & Gas Plasma (GP) displays etc... 13
  14. Unit 1 Introduction to computers LED monitor: • An LED monitor is basically the new version of the LCD monitor that you connect to your computer. LCD monitors used to be lit primarily with CCFL (cold-cathode fluorescent lamps) backlights which contain mercury. LED backlighting is generally thought to be better for the environment since it contains no mercury and uses less power than a CCFL system. There are a few other advantages to an LED monitor. One is that the screen gets brighter faster. A CCFL light has to heat up for a few seconds before it reaches full brightness. This isn't a big deal but it's nice to have. Another advantage of an LED monitor is that the lighting distribution is more even. Since it is lit with many small LEDs rather than one big light source it will generally have less dark or light spots. You will find LED technology in fancy new LCD TVs that are on the market today. The same technology is available in computer monitors and there are many options available. Gas Plasma Displays: This is also called a gas panel or a plasma panel and is another flat screen technology. A plasma panel contains a grid of electrodes in a flat, gas filled panel. the Oeæctrk Oiei•ctric 'aver Font p•ate •ass p hot A schematic matrix electrode configuration in an AC PDP Audio: Composition of plasma display panel The image can persist for a long time without refreshing in this panel. The disadvantages of the gas plasma displays are that they must use AC power and cannot show sharp contrast. Audio is also a type of soft copy. The audio output is through the speakers, headphones etc... Now-a-days a text can be able to convert into Audio too. Digital audio Refers to the reproduction and transmission of sound stored in a digital format. Sound cards enable the computer to output sound through speakers connected to the board, to record sound input from a microphone connected to the computer, and manipulate sound stored on a disk. 14
  15. Unit 1 Introduction to computers Define Operating System? Explain the types of Operat ing Systems? OS is a collection of system programs that together controls the operation of a computer system. Operating system is a platform between hardware and user which is responsible for the management and coordination of activities and the sharing of the resources of a computer. (It hosts the several applications that run on a computer and handles the operations of computer hardware.) There are different types of operating systems. These are as follows: Real-time operating system (RTOS) - Real-time operating systems are used to control machinery, scientific instruments and industrial systems. This system is designed to respond to an event within a pre-determined time. It respond quickly, which are used in flight reservation system, railway reservation system, military applications..etc... (A very important part of an RTOS is managing the resources of the computer so that a particular operation executes in precisely the same amount of time, every time it occurs.) Time-sharing (Multi-user)operating systems: Time sharing is a technique which enables many people, located at various terminals, to use a particular computer system at the same time. Time-sharing or multitasking is a logical extension of multiprogramming. Processor's time which is shared among multiple users simultaneously is termed as time-sharing. Time-Sharing Systems objective is to minimize response time. Multiple jobs are executed by the CPU by switching between them, but the switches occur so frequently. Thus, the user can receive an immediate response. For example, in a transaction processing, processor execute each user program in a short burst or quantum of computation. That is if n users are present, each user can get time quantum. When the user submits the command, the response time is in few seconds at most. Advantages Provide advantage of quick response. Avoids duplication of software. Reduces CPU idle time. Disadvantages Problem of reliability. Question of security and integrity of user programs and data. Problem of data communication Multi-processor OS: It incorporates more than one processor dedicated to the running processors. This technique of using more than one processor is also called parallel processing. The advantage of this system is throughput of processor increased in less time. Multi-programming os: Multiprogramming is a rudimentary form of parallel processing in which several programs are run at the same time on a uni-processor. Since there is only one processor, there can be no true simultaneous execution of different programs. Instead, the operating system executes part of one program, then part of another, and so on. To the user it appears that all programs are executing at the same time. 15
  16. Unit 1 Introduction to computers Embedded System: The operating systems designed for being used in embedded computer systems are known as embedded operating systems. An os that is self-contained in the device and resident in ROM. xplain the graphical user interface (GUI) USER INTERFACE: Operating system organizes applications so that users can easily access them, use them, and store application data. When an application is opened, the operating system lets the application provide the majority of the user interface. The operating system still has the responsibility of providing access to the hardware for whatever the application needs. If the program cannot function properly, the operating system again takes control, stops the application, and displays and error message. An effective interface of an operating system does not concern the user with the internal workings of the system. A good user interface should attempt to anticipate the user's requirements and assist him to gather information and use necessary tools. Common interfaces provided by different operating systems can be categorized as Command Line Interface (CLI) and Graphical User Interface (GUI) COMMAND LINE INTERFACE (CLI): In early days of computing, operating systems provided the user with the facility of entering commands via an interactive terminal. Those were the only means of communication between a program and its user, based solely on textual input and output. Commands were used to initiate programs, applications, and .exe Microsoft Windows LUeps ion 6 -1 .7600] Copyright (c) 2009 Microsoft Corporat ion . Q 11 rights reserved. DOS IS AN EXAMPLE OF LINE INTERFACE THIS IS MS-DOS so on. A user had to learn many commands for proper operation of the system. GRAPHICAL USER INTERFACE (GUI): With the development in chip designing technology, computer hardware became quicker and cheaper, which led to the birth of GUI-based operating system. These operating systems provide users with pictures rather than just characters to interact with the machine. The operating system displays icons, buttons, dialog boxes, etc., on the screen. The user sends instructions by moving pointer on the screen (generally mouse) and selecting certain objects by pressing buttons on the mouse while the mouse pointer is pointing at them. Computer Recycle Bin avast! Free Antivirus Microsoft OfficeWord2007 TypingMaster Pro Paint Pictures Getting Started Windows Media Center Calculator Sticky Notes Control panel pTorrent Dß'ices and Printers Snipping Tool Default Programs Configure Java Help and Support All Programs Search prcyrarns and Ides 2 4 8 10:56 PM 04-Jul-14
  17. Unit 1 Introduction to computers Explain Software, Hardware & relat ion between them? HARD WARE: The term 'hardware' and 'software' are frequently used in computer system. The hardware consists of the physical equipments which makes up the computer system like Monitor, Keyboard, CPU, Hard Disk, Floppy drive, Printer etc. Normally all the items which can seen and touched are hardware items. Thus, storage, processing and control unit, I/O device (input/output device) and peripherals devices — all are hardware. Computer hardware is the physical part of the computer including the digital circuits inside the computer. Hardware includes not only the computer parts but also the cables, connectors, power supply units and peripheral devices such as the keyboard, mouse, audio speakers and printer. Entering and displaying information is carried out on a wide variety of accessory devices called peripherals, also known as input/output (I/O) devices. Some peripherals, such as keyboard is only input devices, other peripherals, such as printer is only output devices and some are both. SOFTWARE: The term 'software' was first used by John W. Tukey in 1958 as the following sense — "In computer science and software engineering, computer software is all computer programs". The most modern software theory was first proposed by Alan Turing in 1935 is — "Computer software, consisting of programs, codes or instructions that enables a computer to perform specific tasks". Software is an ordered sequence of instructions for changing the state of the computer hardware in a particular sequence. In computers, software is loaded into RAM and executed in the central processing unit. RELATIONSHIP BETWEEN HARDWARE AND SOFTWARE: Computer software and computer hardware can exist independently of each other just as a human soul and a human body. The human body does nothing when not indwelt by a soul and the human soul is inaccessible to us on earth after it has separated from its body in death. Likewise, a computer program (software) cannot operate without the computer hardware. The hardware also cannot perform the processes that the software is programmed to perform, unless it has had access to the software to gain the needed instructions, "A Application control operating systems users software keyboard/Mouse printer hardware CPU others computer requires programs to function and a computer program does nothing unless its instructions are executed by a central processor" ("computer program") 17
  18. Unit 1 Introduction to computers Computer software acts as an interface between user and hardware. Software is so called in contrast to computer hardware, which encompasses the physical interconnections and devices required to store and execute (or run) the software. In computer system, both hardware and software work together. Actually, work is done by hardware, whereas software governs what and how to do that. Without software, a computer is just a piece of metal. Explain the CPU? CPU is considered as the brain of the computer; It sends the signals to various parts of the computer, controlling what goes on. A CPU built on a single chip is called a "Microprocessor/Processor". A microprocessor incorporates most or all of the functions of a computers CPU on a single chip Integrated Circuit (IC or Microchip). IC's are made up of capacitors, transistors, and resistors etc... which are hooked up on a fiber-glass board called circuit boards. In a computer, the printed circuit board that connects all parts of the computer together is called motherboard. The CPU performs all types of data processing operations. It receives the input (Data) from the user and converts it into meaningful information (Output). It controls all the internal & external devices connected to it. CPU consists of three main subsystems, which work together to provide operational capabilities to the computer. Arithmetic & Logic Unit: It is responsible for performing the actual computing & carrying out the arithmetic operations & logical operations at very high speed. Control Unit: • Control unit of CPU contains circuitry that uses electrical signals to direct the entire computer system to carry out, or execute, stored program instructions. • This unit checks the correctness of the sequence of operations. It fetches program instructions from RAM, interpret them, & ensure correctness of the program. It controls all parts of the computer & directs the functioning of the other units. Registers: A special purpose, high-speed temporary storage area within the CPU When CPU executes the instructions, there is a transfer of information between various units of the computer. CPU uses the registers to handle the process of execution effectively & efficiently. Registers receive the information, hold it temporarily & pass it on as directed by the Control Unit. Ex: If two numbers are to be multiplied, both numbers must be in registers, and the result is also placed in a register. (The register can contain the address of a memory location where data is stored rather than the actual data itself.) The number of registers that a CPU has and the size of each (number of bits) help determine the power and speed of a CPU. For example a 32-bit CPU is one in which each register is 32 bits wide. Therefore, each CPU instruction can manipulate 32 bits of data. 18
  19. Unit 1 Introduction to computers Define Network? Explain the types of networks € A network is a group of two or more computer systems linked together. Or A computer network or data network is a telecommunications network that allows computers to exchange data. In computer networks, networked computing devices pass data to each other along data connections. The connections (network links) between nodes are established using either cable media or wireless media. LAN - Local-area network: LAN is a computer network that spans a relatively small area. Most LANs are confined to a single building or group of buildings, However, one LAN can be connected to other LANs over any distance via telephone lines and radio waves One computer is designated as File server (which stores all the software that server printer controls the network) and all other computers which are connected to it acts as work stations. This means that many users can share expensive devices, such as laser printers, as well as data. Users can also use the LAN to communicate with each other, by sending e-mail or engaging in chat sessions. LANs are capable of transmitting data at very fast rates, much faster than data can be transmitted over a telephone line; but the distances are limited, and there is also a limit on the number of computers that can be attached to a single LAN. (10 to 100 mbps) CAN — (campus-area network): An interconnection of local-area networks within a limited geographical space, such as a school campus or a military base Campus Area Network (CAN) Buildirg 1 B'Odhg 4 computertipsdo•nload.com The n •st
  20. Unit 1 MAN - (Metropolitan Area Network): A data network designed for a town or city. In terms of geographic breadth, MANs are larger than local- area networks (LANs), but smaller than wide-area networks (WANs). MANs are usually characterized by very high-speed connections using fiber optical cable or other digital media. MAN is a network where all the LAN's are connected each other or the computers are connected by a single network (back bone) MAN may be operated by one organization or be shared resources by several organizations in the same city. WAN - wide area network: WAN is a computer network that spans a relatively large geographical area. Typically, a Introduction to computers MAN ALAN 8 A LAN — City Q.Qa Metropolitan Area Network (MAN) WAN consists of two or more local-area networks (LANs). Computers connected to a wide-area network are often connected through public networks, such as the telephone system. They can also be connected through leased lines or satellites. The largest WAN in existence is the Internet. WAN Wide Area Netwcn Reti Ki!i MAN Metropolitan Area Reti LAN Local Area Reti 'i 20

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