Computer course

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1 COMPUTER COURSE

k.suresh

Introducing Computer Systems
What is Computer? Computer is an advanced electronic device that takes raw data as input from the user and processes these data under the control of set of instructions (called program) and gives the result (output) and saves output for the future use. It can process both numerical and non-numerical (arithmetic and logical) calculations. (OR) A Computer is an electronic device that can perform activities that involve Mathematical, logical and graphical manipulations. Generally, the term is used to describe a collection of devices that function together as a system. A computer has four functions: Input a. accepts data b. processes data c. produces output d. stores results Input (Data): Input is the raw information entered into a computer from the input devices. It is the collection of letters, numbers, images etc. Process: Process is the operation of data as per given instruction. It is totally internal process of the computer system. Output: Output is the processed data given by computer after data processing. Output is also called as Result. We can save these results in the storage devices for the future use. Processing Output Storage

Advantages of computers:
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1 COMPUTER COURSE

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1. High speed: Computers have the ability to perform routine tasks at a greater speed than human beings. They can perform millions of calculations in seconds. 2. Accuracy: Computers are used to perform tasks in a way that ensures accuracy. 3. Storage: Computers can store large amount of information. Any item of data or any instruction stored in the memory can be retrieved by the computer at lightning speeds. 4. Automation: Computers can be instructed to perform complex tasks automatically (which Increases the productivity). 5. Diligence: Computers can perform the same task repeatedly & with the same without getting tired. 6. Versatility: Computers are flexible to perform both simple and complex tasks. 7. Cost effectiveness: Computers reduce the amount of paper work and human effort, thereby reducing costs.



ORGANIZATION OF COMPUTER (OR) FUNCTIONAL UNITS OF A COMPUTER (OR) BLOCK DIAGRAM OF A COMPUTER:

A computer system has the following main components: DR C.S.N DEGREE & P.G COLLEGE BHIMAVARAM 2

1 COMPUTER COURSE 1) Input unit 2) Central Processing Unit (CPU). 3) Output unit.

k.suresh

Input unit:
Input unit accepts coded information from human operators through electromechanical devices such as the keyboard. The information received is either stored in the memory for later reference or immediately used by the Arithmetic and Logic circuitry to perform the desired operation. Finally the result is sent back to the outside through the output unit. Examples: keyboard, Joy stick, track ball, mouse (pointing devices), scanner etc.

Central Processing Unit:
Central Processing Unit (CPU) is the main component or “brain” of a computer. It performs all the processing of input data. Its examine and execute the instructions stored in the main memory of a computer. In microcomputers, CPU is built on a single chip or Integrated Circuit (IC) and is called a microprocessor. A CPU consists of the following distinct parts: • Arithmetic Logic Unit (ALU) • Control Unit (CU) • Registers • Buses • Clock

. Memory unit
Arithmetic Logic Unit (ALU): The arithmetic and logic unit of CPU is responsible for all arithmetic operations like addition, subtraction, multiplication and division as well as logical operations, such as less than, equal to and greater than. All calculations and comparisons are performed in arithmetic logic unit.

Control Unit: DR C.S.N DEGREE & P.G COLLEGE BHIMAVARAM 3

1 COMPUTER COURSE

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The control unit is responsible for controlling the transfer of data and instructions among other units of a computer. It is considered as the “central nervous system” of a computer as it manages and coordinates all the units of computer. It also performs the physical data transfer between memory and hardware devices. . Registers: Data is temporarily stored in small, local memory locations of 8, 16, 32 or 64 bits called registers. Depending on the type of processor, the overall number of registers can vary from about ten to many hundreds. The main registers are: The accumulators register (ACC), which stores the results of arithmetic and logical operations. The status register (PSW, Processor Status Word), which holds system status indicators (carry digits, overflow, etc.); The instructions register (RI), which contains the current instruction being processed; The ordinal counter (OC or PC for Program Counter), which contains the address of the next instruction to process; The buffer register, which temporarily stores data from the memory. Buses: Data is stored as a unit of eight bits (bit stands for binary digit, i.e. 0 or 1) in a register. Each bit is transferred from one register to another by means of a separate wire. This group of eight wires that is used as a common way to transfer data between registers is known as a bus. It is actually a connection between two components to transmit signal between them. A bus can be of three major types. These types are as follows: 1. Data bus-- It is used to move data. 2. Control bus-- It is used to move address or memory location. 3. Address bus-- It is used to send control signals between various components of a computer. Clock: A clock is another important component of CPU. It measures and allocates a fixed time slot for processing each and every micro computer. The clock speed of CPU varies from one model to another in the range 4.77 MHz (in 8088 processor) to 266 MHz (in Pentium II). The speed of CPU is also specified in terms of Millions of Instructions Per Second (MIPS) or Million of Floating Point Operations Per Second (MFLOPS). DR C.S.N DEGREE & P.G COLLEGE BHIMAVARAM 4

1 COMPUTER COURSE

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Memory Unit:
Memory unit is that component of a computer system which is used to store data, instructions and information before and after the processing by ALU. It is actually a work area within a computer where CPU stores data and instructions. It is also known as a main memory or primary or internal memory.

Output unit:
Output unit accept binary data from the computer and decodes it into original form and supplies this result to the outside world. E.g. monitor, Printer, Video terminals (provides both input & output functions), graphic displays etc GENERATION OF COMPUTERS (History of computers): The first electronic computer was designed and built at the University of Pennsylvania based on vacuum tube technology. Vacuum tubes were used to perform logic operations and to store data. Generations of computers has been divided into five according to the development of technologies used to fabricate the processors, memories and I/O units. I Generation: 1945 – 55 II Generation: 1955 – 65 III Generation: 1965 – 75 IV Generation: 1975 – 89 V Generation: 1989 to present



First Generation (1945 – 55):
1. In this generation “Vacuum tubes” were used for basic arithmetic operations. 2. Took few milliseconds for processing Bulky data. 3. This computer cost is very high and speed is low and consumes more power with limited performance. 4. In this time assembly language is used to prepare programs. These were translated into machine level language for execution. 5. Punched cards and paper tape were invented to store programs and data and to get results. 6. Magnetic tape / magnetic drum were used as secondary memory storage devices. 7. It was mainly used for scientific computations. DR C.S.N DEGREE & P.G COLLEGE BHIMAVARAM 5

1 COMPUTER COURSE 8. 1st generation computers are called: (ENIAC - Electronic Numerical Integrator and Calculator

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EDSAC – Electronic Delay Storage Automatic Calculator EDVAC–Electronic Discrete Variable Automatic computer UNIVAC – Universal Automatic Computer IBM 701)

Second Generation (1955 – 65):
1. In this generation “Transistors” were used in place of vacuum tubes. (Invented at AT&T Bell lab in 1947). 2. The size of computers is small and less power consumption and better performance, Lower cost. 3. In this generation, High level languages such as FORTRAN, COBOL etc were used for prepare programs, the high-level program translate into corresponding assembly language program which was then translated into machine language using with Compilers. 4. The Magnetic ferrite core memories were used as main memory which is a “randomaccess non-volatile memory”. 5. Magnetic tapes and magnetic disks were used as secondary memory, and also Punched cards continued during this period. 6. Hardware for floating point arithmetic operations was developed and Index registers were introduced which increased flexibility of programming. 7. Separate input-output processors were developed that could operate in parallel with CPU. 8. It was used in business, industry and commercial organizations for preparation of payroll, inventory control, marketing, production planning, research, scientific & engineering analysis and design etc. 9. In 2nd generation computers are called: (Manufacturers – IBM 7030, Digital Data Corporation’s PDP 1/5/8, Honeywell 400).

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Third Generation (1965 – 75):
1. In this generation “IC” (Integrated circuits) was used for basic operations. 2. Small Scale Integration and Medium Scale Integration technology were also implemented in CPU, I/O processors etc. 3. The size of computer is Smaller & better performance and lesser cost and Faster processors. 4. In the generation magnetic core memories were replaced by semiconductor memories (RAM & ROM) 5. The High level languages were standardized by ANSI eg. ANSI FORTRAN, ANSI COBOL. 6. Introducing Microprogramming, parallel processing, pipelining, multiprocessor system, multiprogramming, multi-user system (time shared system) etc. 7. The Operating system software was introduced (efficient sharing of a computer system by several user programs). 8. Cache and virtual memories were introduced (Cache memory makes the main memory appear faster than it really is. Virtual memory makes it appear larger) 9. It was used in Database management, multi-user application, online systems like closed loop process control, airline reservation, interactive query systems, automatic industrial control etc. 10. In 3rd generation computers are called: (System 360 Mainframe from IBM, PDP-8 Mini Computer Corporation). from Digital Equipment

Fourth Generation (1975 – 89):
1. VLSI (Very Large Scale Integrated Circuits) was used for basic operations. 2. VLSI design with Tens of thousands of transistors can be placed in a single chip. 3. It consumes less power with high performance, lower cost and very compact and much increase in the speed of operation. 4. In this time Semiconductor memory chips were used as the main memory. 5. CRT screen, laser & ink jet printers, scanners are also developed. 6. The Secondary storage memories, i.e. hard disks, Floppy disks & magnetic tapes were used for backup memory. DR C.S.N DEGREE & P.G COLLEGE BHIMAVARAM 7

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7. The Parallelism, pipelining cache memory and virtual memory were applied in a better way. 8. In this generation LAN and WANS were developed used for desktop work stations interconnected. 9. C language, Unix OS, and Graphical User Interface was introduced. 10. In 4th generation computers are called: (Intel’s 8088,80286,80386,80486 .., Motorola’s 68000, 68030, 68040, Apple II, CRAY I/2/X/MP etc).

Fifth Generation (1989 to at present):
1. Introduced ULSI (Ultra Large Scale Integration) technology is developed for operations. For example Intel’s Pentium 4 microprocessor contains 55 million transistors millions of components on a single IC chip. 2. In this generation also developed Superscalar processors, Vector processors, SIMD processors, 32 bit micro controllers and embedded processors, Digital Signal Processors (DSP) etc. 3. The Object oriented language like JAVA for developed internet programming and new operating systems Windows 95/98/XP/…, LINUX, etc were developed. 4. The Computers based on artificial intelligence and Portable note book computers introduced in this time. 5. Computers are used base on extensive parallel processing, multiple pipelines, multiple processors, massive parallel machines and extensively distributed system connected by communication networks etc. 6. In this time also Introduced World Wide Web and other existing applications like e-mail, e-Commerce, Virtual libraries/Classrooms, multimedia applications etc. 7. Memory chips up to 1 GB, hard disk drives up to 180 GB and optical disks up to 27 GB are available (still the capacity is increasing). Storage technology and advanced large main memory and disk storage available. 8. The Quantum mechanism and nanotechnology will radically change the phase and variation of computers. 9. In this generation computers are called: (IBM notebooks, Pentium PCs-Pentium 1/2/3/4/ Dual core/Quad core, SUN work stations, Origin 2000, PARAM 10000, IBM SP/2). DR C.S.N DEGREE & P.G COLLEGE BHIMAVARAM 8

1 COMPUTER COURSE  COMPUTERS FOR INDIVIDUAL USERS (or) TYPES OF COMPUTERS (or)

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CLASSIFICATIONS OF COMPUTERS (or) COMPUTERS FOR ORGANIZATIONS: Most computers arc meant to be used by only one person at a time. Such computers are often shared by several people (such as those in your school’s computer lab), but only one user can work with the machine at any given moment. The primary types of computers in this category are: 1. Mainframe Computers 2. Minicomputers: 3. Supercomputers

Mainframe Computers:
Mainframe computers are used in large organizations such as insurance companies and banks, where many people frequently need to use the same data. In a traditional mainframe environment, each user accesses the mainframe’s resources through a device called a terminal. There are two kinds of terminals, A dumb terminal does not process or store data; it is simply an input/output (I/O) device that functions as a window into a computer located somewhere else. An intelligent terminal can perform some processing operations, but it usually does not have any storage. In some mainframe environments, however, workers can use a standard personal computer to access the mainframe. Examples of mainframe computers are: Univac 1180, and DEC. IBM 3000 series, Burroughs B7900,

Minicomputers:
It was first released in the 1960s. Minicomputers are small size compared to other computers of the day. The capabilities of a minicomputer are somewhere between those of mainframes and personal computers. For this reason, minicomputers are often called “midrange computers”. Minicomputers can handle much more input and output than personal computers. Although some mini computers are designed for a single user, the most powerful minicomputers can serve the input and output needs of hundreds of users at a time. Users can access a central minicomputer through a terminal or a standard PC. Examples of mini computers are Digital Equipments PDP 11/45 and VAX 11. DR C.S.N DEGREE & P.G COLLEGE BHIMAVARAM 9

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Super computers
Supercomputers are the most powerful computers made, and physically they are some of the largest. These systems can process huge amounts of data, and the fastest. Super computers can perform more than one trillion calculations per second. Some supercomputers can contains thousands of processors. Supercomputers are ideal for handling large and highly complex problems that require extreme calculating power. For example, supercomputers have long been used in the mapping of the human genome, forecasting weather, and modeling complex processes like nuclear fission. Examples of super computers are CRAY Research :- CRAY-1 & CRAY-2, Fujitsu (VP2000), Hitachi (S820), NEC (SX20), PARAM 10000 by C-DAC, Anupam by BARC, PACE Series by DRDO.

Micro Computers:
They are designed to be used by only one person at a time. A microcomputer uses a microprocessor as its central Processing Unit (CPU). Microcomputers are tiny computers that can be different in size from a single chip to the size of a desktop model. It’s having Small to medium data storage capacities 500MB – 2GB.The common examples of microcomputers are chips used in washing machines, TVs, Cars and Note book/Personal computers. Examples of super computers are: IBM PC, PS/2 and Apple Macintosh This can be divided based on sizes as fallows: a. Desktop computers. b. Workstations. c. Notebook computers. d. Tablet computers. e. Handheld computers. f. Smart phones. Desktop computers: The desktop computer is a Personal Compute. That is designed to sit on (or under) a desk or table. These are the systems you sec all around you, in schools, homes, and offices. Desktop computers are more powerful and are used for an amazing array of tasks or jobs with greater easy and efficiency. But they can be also used to communicate, produce music, edit photographs and videos, play sophisticated games. But it was much more used by everyone from preschoolers (L.K.G) to nuclear physicists; desktop computers are indispensable for learning, work, and play. DR C.S.N DEGREE & P.G COLLEGE BHIMAVARAM 10

1 COMPUTER COURSE Workstations:

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A workstation is a specialized; single-user computer that typically has more power and features than a standard desktop PC. These machines are popular among scientists, engineers, and animators who need a system with greater-than-average speed and the power to perform sophisticated tasks. Workstations often have large, high-resolution monitors and accelerated graphics handling capabilities, making them suitable for advanced architectural or engineering design, modeling, animation, and video editing. Notebook Computers: Notebooks computers are approximate the shape of notebook and easily fit inside a briefcase. Because people frequently set these computers on their lap, they are also called laptop computers. Notebook computers can operate on alternating current or special batteries. These computers is generally weigh less than eight pounds, and some of weigh less than three pounds based on a thin monitor and a keyboard and easy storage. Notebooks are fully functional microcomputers; the people who use them need the power of a full-size desktop computer. Tablet PCs: The tablet PC is the newest development in portable, full-featured computers). Tablet PCs offer all the functionality of a notebook PC, but they are lighter and can accept input from a special pen called a stylus or a digital pen. That is used to tap or write directly on the screen. Many tablet PCs also have a built-in microphone and special software that accepts input from the user's voice. A few models even have a fold-out keyboard, so they can be transformed into a standard notebook PC. Tablet PCs run specialized versions of standard programs and can be connected to a network. Some models also can be connected to a keyboard and a full size monitor. Handheld PCs: Handheld personal computers are computing devices small enough to fit in your hand. A popular type of handheld computer is the personal digital assistant (PDA). A PDA is no larger than a small appointment book and is normally used for special applications, such as taking notes, displaying telephone numbers and addresses, and keeping track of dates or agendas. Many PDA’s can be connected to larger computers to exchange data. Most PDAs come with a pen that lets the user write on the screen. Some handheld computers feature tiny built-in keyboards or microphones that allow voice input. DR C.S.N DEGREE & P.G COLLEGE BHIMAVARAM 11

1 COMPUTER COURSE Smart Phones:

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Some cellular phones double as miniature PCs. Because these phones offer advanced features not typically found in cellular phones, they are sometimes called smart phones. These features can include Web and c-mail access, special software such as personal organizers, or special hardware such as digital cameras or music players. Some models even break in half to reveal a miniature keyboard.



WHAT ARE THE INITIAL PARTS OF A COMPUTER SYSTEM?
Computers come in many varieties, from the tiny computers built into household appliances, to the astounding supercomputers that have helped scientists map the human genome. But no matter how big it is or how it is used, every computer is part of a system. A complete computer system consists of four parts: 1. Hardware 2. Software 3. Data 4. User

Hardware:
The mechanical devices that make up the computer are called hardware. Hardware is any part of the computer you can touch. A computer’s hardware consists of interconnected electronic devices that you can use to control the computer’s operation, input, and output. (The generic term device refers to any piece of hardware.) Hardware refers to any physical component of computer. For example, CPU, monitor (VDU), keyboard, hard disk, floppy disk, printer etc. are physical components and, thus, are all hardware.

Software:
Software is a “set of instructions that makes the computer perform tasks and software tells the computer what to do”. (The term program refers to any piece of software.) Some programs exist primarily for the computer's use to help it perform tasks and manage its own resources. Other types of programs exist for the user, enabling him or her to perform tasks such as creating documents. Thousands of different software programs arc available for use on personal computers. DR C.S.N DEGREE & P.G COLLEGE BHIMAVARAM 12

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For example: DOS (Disk Operating System), BASIC, COBOL, dBase, Accounting Software etc.

Data:
Data consist of individual facts, figures or pieces of information that by themselves may not make much sense to a person. A computer’s primary job is to process these tiny pieces of data in various ways, converting them into useful information.

Users:
People are the computer operators, also known as users. It can be argued that some computer systems are complete without a person’s involvement; however, no computer is totally autonomous. Even if a computer can do its job without a person sitting in front of it, people still design, build, program, and repair computer systems. This lack of autonomy is especially true of personal computer systems, which arc the focus of this book and are designed specifically for use by people.



WHAT ARE THE “INPUT DEVICES”?
1. Keyboard: 2. Mouse: 3. Scanner: 4. Track ball: 5. Track pad or touchpad: 6. Touch Screen: 7. Light pen: 8. Joystick: 9. Optical Mark Reader (OMR): 10.Bar Code Reader: 11.Optical Character Reader (OCR): 12.Magnetic Ink Character Recognition (MICR):

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1 COMPUTER COURSE KEYBOARD:

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KEY BOARD: 1. Keyboard is the main input device of a computer (similar to a typewriter). 2. It contains three types of keys alphanumeric keys. Modifier keys. Numeric keys. Special keys. Function keys. 3. The function of each and every key can be well understood only after working on a PC. When any key is pressed, an electronic signal is produced. This signal is detected by a keyboard encoder that sends a binary code corresponding to the key pressed to the CPU. 4. There are many types of keyboards but 101 keys keyboard is the most popular one.

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1 COMPUTER COURSE The Alphanumeric Keys:

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The alphanumeric keys are looks like a typewriter's keys. Those are arranged the same way on almost every keyboard. Sometimes this common arrangement is called the QWERTY layout. Because the first six keys on the top row of letters are Q, W, E, R, T, and Y. Along with the keys that produce letters and numbers. The alphanumeric key group includes four keys having specific functions. The TAB, CAPS LOCK, BACKSPACE, and ENTER keys are described Alphanumeric keys. That are used to type all alphabets, numbers and special symbols like $, %, @, A etc. The Modifier Keys: The SHIFT, ALT (Alternate), and CTRL (Control) keys are called modifier keys. because they modify the input of other keys. In other words, if you hold down a modifier key while pressing another key, then you are changing the second key's input in some way. For example, if you press the J key, you input a small letter. But if you hold down the SHIFT key while pressing the J key, you input a capital. Modifier keys arc extremely useful because they give all other keys multiple capabilities. The Numeric keys: The numeric keypad is usually located on the right side of the keyboard. The numeric keypad looks like a calculator's keypad, with its 10 digits (0 to 9) mathematical operators (+, -, *, and /). The numeric keypad also features a NUM LOCK key, which forces the numeric keys to input numbers. When NUM LOCK is deactivated, the numeric keypad's keys perform cursor movement control and other functions. The Function Keys: The Function keys such as <Fl>, <F2>, <F3>……. <f12>.are used to give special commands depending upon the software used. They are usually arranged in a row along the top of the keyboard. They allow you to input commands without typing long strings of characters or navigating menus or dialog boxes. Each function key's purpose depends on the program you are using. For example, in most programs, Fl is the help key. When you press it, a special window appears to display information about the program you are using. Most IBM-compatible keyboards have 12 function keys. Many programs use function keys along with modifier keys to give the function keys more capabilities. DR C.S.N DEGREE & P.G COLLEGE BHIMAVARAM 15

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*(POINTING DEVICES) MOUSE:
A mouse is an input device that you can move around on a flat surface (usually on a desk or keyboard tray) and controls the pointer. The pointer (also called the mouse pointer) is an onscreen object, usually an arrow, that is used to select text; access menus; and interact with programs, files, or data that appear on the screen. Figure 2A.11 shows an example of a pointer in a program window. The mouse can mainly divided into two types: 1. The mechanical mouse 2. The optical mouse. The MECHANICAL MOUSE is the most common type of pointing device. A mechanical mouse contains a small rubber ball that can see through a hole in the bottom of the mouse's case. The ball rolls inside the case when you move the mouse around on a flat surface. So Inside the mouse, the rollers and sensors send signals to the computer, telling it the distance, direction, and speed of the ball's motions. The computer uses this data to position the mouse pointer on the screen.

The OPTICAL MOUSE is a non-mechanical mouse. This type of mouse emits a beam of light from its underside. It uses the light's reflection to judge the distance, direction, and speed of its travel.

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1 COMPUTER COURSE Uses of Mouse:

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You use a mouse to move the pointer to a location on the screen, a process called pointing. Everything you do with a mouse is accomplished by combining pointing with four techniques: a. Clicking b. Double-clicking c. Dragging d. Right-clicking Clicking is used for click an item with the mouse and move the pointer to the item on the screen. When the pointer touches the object, quickly press and release the primary mouse button once. Clicking or single clicking is the most important mouse action. To select any object on the screen, such as a menu, command, or button, you click it. Double-clicking means pointing to the item with the mouse pointer and then pressing and releasing the mouse button twice in rapid succession. Double-clicking is primarily used with desktop objects such as icons. For example, you can double-click a program's icon to launch the program. Dragging an item means positioning the mouse pointer over the item, pressing the left mouse button, and holding it down as you move the mouse. As you move the pointer, the item is “dragged” along with it across the screen. You can then drop the item in a new position on the screen. This technique is also called drag-and-drop editing, or just drags and drop. Right-clicking means pointing to an item on the screen, then pressing and releasing the right mouse button. Right-clicking usually opens a shortcut menu that contains commands and options that pertain to the item to which you are pointing.

SCANNER:
A scanner is widely used in Desktop Publishing (DTP) applications. It is used for digitizing images such as photographs, forms, documents etc. There are many types of scanners which can also read text by converting them to digital code. The scanners are very useful for converting the typed pages into word processing files. Graphic scanners convert a printed image into video image without converting it to digital code.\ DR C.S.N DEGREE & P.G COLLEGE BHIMAVARAM 17

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TRACK BALL:
A trackball is a pointing device. That works like an upside-down mouse. You put your second finger or thumb on an exposed ball, then place your other fingers on the buttons. You roll the ball with your second finger or thumb for move the pointer around the screen. But you do not move the whole device. a trackball requires less space than a mouse. Trackballs come in different models. Some trackballs are large and heavy with a ball about the same size as a cue ball. Most trackballs having two buttons, although three-button models are also available. Trackball units also are available in right- and left-handed models.

TRACKPAD OR TOUCHPAD:
The track pad also called a touchpad. It is a pointing device that many people find less tiring to use than a mouse or trackball. The movement of a finger across a small touch-sensitive surface is translated into pointer movement on the computer screen. The touch pad surface may be only 1.5 or 2 inches square. The track pad’s size also makes it suitable for a notebook computer. Some notebook models feature a built-in track pad rather than a mouse or trackball. Track pads include two or three buttons, which perform the same functions as mouse buttons. Some track pads arc also “strike sensitive," meaning you can tap the pad with your fingertip instead of using its buttons.

TOUCH SCREEN:
It allows the user to operate/selections by simply touching the display screen. Some special VDU devices have touch screens. These screens are sensitive to human fingers and act as tactile input devices. Using touch screen, the user can point to a selection on the screen instead of pressing keys. Touch screen helps users to get information quickly. It is mainly used in hotels or airports to convey information to visitors. Common examples of touch screen include information kiosks, and bank ATMs.

LIGHT PEN:
Light pen similar to a pen and it is a pointing device. This is used to select a displayed menu item or draw pictures on the monitor screen. It consists of a photocell and an optical system placed in a small tube. When its tip is moved over monitor and pen button is pressed, its photocell-sensing element detects the screen location and sends corresponding signal to CPU. DR C.S.N DEGREE & P.G COLLEGE BHIMAVARAM 18

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JOYSTICK:
Joystick is also a pointing device used to move cursor position on a monitor screen. It is a stick having a spherical ball at its both lower and upper ends. The lower spherical ball moves in a socket. It can be moved in all the four directions. The function of a joystick is similar to that of a mouse. It is mainly used in Computer-Aided Designing (CAD) and playing computer games.

OPTICAL MARK READER (OMR):
Optical Mark Reader (OMR) is a special type of optical scanner used to recognize the type of mark made by pen or pencil . It is especially used for checking answer sheets of examination having multiple-choice questions. The answer sheet contains special marks such as squares or bubbles. The student fills in these squares with soft pencil or ink to indicate the correct choice. The OMR detects these marks and sends corresponding signals to the processor. If a mark is present, the amount of reflected light is reduced. OMR detects the presence of mark for each and every answer. These are widely used for almost all competitive examinations having objective type questions.

BAR CODE READER:
Bar code reader is an optical scanner used for reading bar coded data (data in the form of light and dark lines). The bar coded data consists of a number of bars of varying thickness and spacing between them. The bar code reader reads the bar coded data and converts it into electrical pulses which are then processed by computer. Bar coded data is generally used in labeling goods, numbering the books, or encoding ID or A/c numbers.

OPTICAL CHARACTER READER (OCR):
Optical Character Reader (OCR) is an optical scanner which is capable of identifying Alphanumeric characters typed or printed on paper using an OCR font. The text which is to be scanned by a low frequency light source. The dark areas on the text collect the light while light areas reflect it. The photocells of OCR device receive this reflected light and provide binary data corresponding to dark and light areas. OCR devices are used for large volume applications like reading of passenger tickets, computer printed bills of credit card companies and ZIP codes in postal services. DR C.S.N DEGREE & P.G COLLEGE BHIMAVARAM 19

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MAGNETIC INK CHARACTER RECOGNITION (MICR):
“Magnetic Ink Character Recognition” (MICR) is used to recognize the magnetically charged characters mainly found on bank cheques. The magnetically charged characters are written by special ink called “magnetic ink”. MICR device reads the patterns of these characters and compares them with special patterns stored in memory.

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WHAT ARE THE OUTPUT DEVICES:
(Monitors, printers

and plotters)

MONITORS:
The monitor is the most commonly used output device on most personal computer systems. When you are typing a letter, copying files, or surfing the Internet that are looking at your monitor. They want to see whether the image is crisp and clear and how well graphics are displayed on the monitor. Two important hardware devices determine the quality of the image you see on any monitor: (1) The monitor (2) The video controller. Color monitors can display between 16 colors and 16 million colors. Today, most new monitors display in color. Many color monitors can be set to work in monochrome or grayscale mode. The monitors can be divided into to types based on color: Monochrome monitors: It can display only one color that is black. (Such as green, amber, or white) against a contrasting background. These monitors are used for only displays “text”. Where the user does not need to see color graphics. Grayscale monitors: It can display various intensities of gray from a very little gray to black against a white or off-white background. And these are essentially a type of monochrome monitor. Grayscale flat panel displays are used in low-end portable systems. There are two types of monitors are used with PCs. A cathode ray tube (CRT) A flat-panel display 1). A cathode ray tube (CRT): 1. The cathode ray tube (CRT) monitor comes with most desktop computers. 2. It looks a television screen. This type of monitor uses a large vacuum tube for display. 3. The CRT monitor works from back o f a monitor's housing is an electron gun. 4. The gun shoots a beam of electrons through a magnetic coil called a yoke. This aims the beam at the front of the monitor. 5. The back of the monitor’s screen is coated with phosphors, chemicals that glow when they are struck by the electron beam. 6. The screen’s phosphor coating is organized into a grid o f dots. 7. The smallest number of phosphor dots that the gun can focus on is called a pixel. DR C.S.N DEGREE & P.G COLLEGE BHIMAVARAM 21

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8. The Pixel is a contraction of the term picture element. Each pixel has a unique address, which the computer uses to locate the pixel and control its appearance. Some electron guns can focus on pixels as small as a single phosphor dot. 9. The electron gun does not just focus on a spot and shoot electrons at it. 10. It systematically aims at every pixel on the screen, starting at the top left corner and scanning to the right edge. Then it drops down a tiny distance and scans another line. 11. A CRT monitor contains a shadow mask, it is a fine mesh made of metal, fitted to the shape and size of the screen. 12. The holes in the shadow mask’s mesh are used to align the electron beams, to ensure that they strike precisely the correct phosphor dot. In most shadow masks, these holes are arranged in triangles. CRT monitors have long been the standard for use with desktop computers because they provide a bright, dear picture at a relatively low cost.

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1 COMPUTER COURSE 2). A flat-panel display:

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The Flat-panel monitors have been used primarily on portable computers. a new generation of large, high-resolution, flat-panel displays is gaining popularity among users of desktop systems. These new monitors provide the same viewable area as CRT monitors, but they take up less desk space and run cooler than traditional CRT monitors. There are several types of flat-panel monitors: I). Liquid crystal display (LCD): The LCD monitor creates images with a special kind of liquid crystal. That is normally transparent but becomes opaque when charged with electricity. LCD monitors is that their images can be difficult to see in bright light. For this reason, laptop computer users often look for shady places to sit when working outdoors or near windows. A bigger disadvantage of LCD monitor is their limited viewing angle. That is the angle from which the display's image can be viewed clearly. You can sec the image clearly even when standing at an angle to the screen with most CRT monitors. In LCD monitors the viewing angle shrinks and as you increase your angle to the screen, the image becomes fuzzy quickly. II). The passive matrix LCD: The passive matrix LCD works based on transistors for each row and each column of pixels. A grid that defines the location of each pixel. The color displayed by a pixel is determined by the electricity coming from the transistors at the end of the row and the top of the column. Another disadvantage is that they don’t “refresh” the pixels very quickly. If you move the pointer too quickly, it seems to disappear an effect known as submarining. Animated graphics can appear blurry on a passive matrix monitor. Other Types of Monitors Depending upon the resolution, monitors can be classified as follows: a. CGA: (Color Graphics Adapter): It is a circuit board introduced by IBM and the first graphics standard for the IBM PC. With a CGA monitor, it is harder to read than with a monochrome monitor, because the CGA (320 X 200) has much fewer pixels than the monochrome monitor (640 X 350). It supports 4 colors.

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1 COMPUTER COURSE b. EGA: (Enhanced Graphics Adapter):

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EGA is a video display standard that has a resolution of 640 by 350 pixels and supports 16 colors. EGA supports previous display modes and requires a new monitor. c. VGA: (Video Graphics Array) t This is a video display standard that provides medium to high resolution. In a text mode, the resolution of this board is 720 by 400 pixels. It supports 16 colors with a higher resolution of 640 by 480 pixels and 256 colors with 320 X 200 pixels. d. Super VGA: This is a very high resolution standard that displays up to 65,536 colors. Super VGA can support 16.8 million colors at 800 by 600 pixels and 256 colors at 1024 by 768 pixels. A high-priced super VGA allows 1280 by 1024 pixels. Larger monitors (17" or 21" and larger) with a high resolution of 1600 by 1280 pixels are available. VESA (Video Electronics Standards Association) has set a standard for super VGA.

PRINTERS:
A printer is an output device that produces a hard copy of data. The resolution of printer output is expressed as DPI. Printers can produce text and images on paper. Paper can be either separate sheets such as A4 A5 A3 etc. or they may be able to print on continuous (fanfold) paper that feed through the machine.

Daisy-Wheel, Chain Printer,

Drum printer

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1) Impact Printers:
In this hammers or pins strike against a ribbon and paper to print the text. This mechanism is known as electro-mechanical mechanism. They are of two types. (i) (ii) (iii) (iv) (v) (vi) Character Printer: It prints only one character at a time. It has relatively slower speed. E.g. Of them are Dot matrix printers. Dot Matrix Printer: Dot-matrix printers print about 40-300 characters per second (cps) and can print some graphics, although the reproduction quality is poor. Colour ribbons are available for limited use of colour. Dot-matrix printers are noisy, inexpensive, and they can print through multipart forms, creating several copies of a page at the same time, Line Printer: It is a high-speed printer capable of printing an entire line at one time. A fast line printer can print as many as 3,000 lines per minute. The disadvantages of line printers are that they cannot print graphics, the print quality is low, and they are very noisy. Daisy-Wheel Printer: Daisy-Wheel is a printer mechanism that uses any kind of hub (wheel) having a set of spokes at the margin of the hub. The wheel can be removed to use a different character set. The end of each spoke is a raised image of a type character. When the wheel is turned and the required character is aligned to the print hammer, the character is then struck into a ribbon and onto a paper with the hammer. Daisy-wheel printers cannot print graphics, and in general they are noisy and slow, printing from 10 to about 75 characters per second. DR C.S.N DEGREE & P.G COLLEGE BHIMAVARAM 25 Character Printer Dot matrix printer Line Printer Daisy-Wheel Printer Drum printer Chain Printer

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Drum printer: In which each complete set of characters for each print position on a line is on a continuously rotating drum behind an inked ribbon. In front of the ribbon identical character’s are printed continues with a ribbon at all required position on a line. Chain Printer: It is the character printer. The print element in a chain printer is a metallic band or chain containing the embossed characters that rotates horizontally in front of paper. A complete chain consists of the five sections; each section consists of 48 characters. As the print chain rotates, properly timed print hammers strike the paper along with linked ribbon, against the proper character on the chain as it passes. Chain printers are one of the fastest impact printers that can produce up to 400 to 2500 characters per second. Chain Printer also called band printers, contain characters on a rotation band. Speeds of up to 3000 lines a minute may be possible with these machines.

2) Non-Impact Printers:
There printers use non-Impact technology such as ink-jet or laser technology. There printers provide better quality of O/P at higher speed. Non-impact printers, used almost everywhere now, are faster and quieter than impact printers because they have fewer moving parts. Non-impact printers form characters and images without direct physical contact between the printing mechanism and the paper. These printers are of two types: 1. Ink-Jet Printer: 2. Laser Printer:

Ink-Jet Printer:
Ink-jet printers also print images with little dots. Ink-jet printers spray small, electrically charged droplets of ink from four nozzles through holes in a matrix at high speed onto paper. Ink-jet printers can print in colour and are quieter and much less expensive than a colour laser printer. However, they are slower and print in a somewhat lower resolution (300720 dpi) than laser printers. Some new, expensive ink-jet printers print up 1200 or 1400 dpi. DR C.S.N DEGREE & P.G COLLEGE BHIMAVARAM 26

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The another type of ink-jet technology is the bubble-jet printer, which use miniature heating elements to force specially formulated inks through print heads with 128 tiny nozzles. The multiple nozzles print fine images at high speeds . This technology is commonly used in portable printers.

Laser Printer:
Laser Printer is a type of printer that utilizes a laser beam to produce an image on a drum. The light of the laser alters the electrical charge on the drum wherever it hits. The drum is then rolled through a reservoir of toner, which is picked up by the charged portions of the drum. Finally, the toner is transferred to the paper through a combination of heat and pressure. This is also the way copy machines work. Because an entire page is transmitted to a drum before the toner is applied, laser printers are sometimes called page printers. There are two other types of page printers that fall under the category of laser printers even though they do not use lasers at all. One uses an array of LEDs to expose the drum and The other uses LCDs. Once the drum is charged, however, they both operate like a real laser printer. One of the chief characteristics of laser printers is their resolution – how many dots per inch (dpi) they lay down. The available resolutions range from 300 dpi at the low end to 1,200 dpi at the high end.

PLOTTERS:
A plotter is a computer printing device for printing vector graphics. In previous days, plotters were widely used in computer-aided design applications. Though they have generally been replaced with wide-format conventional printers. It is now common place to refer to such wide-format printers as "plotters," Plotter is a device that draws pictures on paper based on commands from a computer. Plotters different from printers in that they draw lines using a pen. As a result, they can produce continuous lines, whereas printers can only simulate lines by printing a closely spaced series of dots. Multi colour plotters use different-collared pens to draw different colours. In general, plotters are considerably more expensive than printers. They are used in engineering applications where precision is mandatory.

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PROCESSING DATA
 HOW REPRESENT DATA COMPUTERS? The data can be represented in computers in different ways. They are: 1) Number system( Binary number, and Decimal number ) 2) Bits and bytes. 3) Text codes (EBCDIC, ASCII,EASCII, and UNICODE) 1. Number system: Most modern computer systems do not represent numeric values using the decimal system. Instead, they typically use a binary or two’s complement numbering system. To understand the limitations of computer arithmetic, you must understand how computers represent numbers. These are two types of number system used to represent data: a. Binary Number System b. Decimal number system a. Binary Number System: Digital computers internally use the binary number system (base 2) to represent data and perform arithmetic calculations. The binary number system is very efficient for computers, but not for humans. Representing even relatively small numbers with the binary system requires working with long strings of 1 and 0. Most modern computer systems (including the IBM PC) operate using binary logic. These two values, co-incidentally, correspond to the two digits used by the binary numbering system. Therefore, it is very easy to convert a binary number to decimal. For each “1” in the binary string, add in 2n. Where “n” is the zero-based position of the binary digit.

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2. BITS AND BYTES: A bit is the smallest possible unit of data a computer can recognize or use. A binary digit is a single numeral in a binary number. Each 1 and 0 in the number below is a binary digit: – 1 0 0 1 0 1 0 1. The term “binary digit or binary integer” is commonly called a “Bit.” A group of eight bits is called a “Byte”. Half of a byte is called a “nibble”. With one byte, the computer can represent one of 256 different symbol s or characters because the eight 1s and 0 s is can be combined in 256 different ways. DR C.S.N DEGREE & P.G COLLEGE BHIMAVARAM 29

1 COMPUTER COURSE 3. TEXT CODES:

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Early programmers realized that they needed a standard text code that was agreeable to all of them. In such a system, numbers would represent the letters of the alphabet, punctuation marks, and other symbols. This standard code system would enable any programmer or program to use the same combinations of numbers to represent the same individual pieces of data. The four most popular text code systems invented are the following: I) EBCDIC: EBCDIC (pronounced EB-si- dic) stands for Extended Binary Coded Decimal interchange Code. EBCDIC b an eight-bi t code that defines 256 symbols. It is still used in IBM mainframe and midrange systems, but it is rarely encountered in personal computers. II) ASCII: ASCII (pronounced AS-key) stands for the American Standard Code for Information Interchange. Today, the ASCII character set is by far the most commonly used in computers of all types. ASCII is an eight-bi t code that specifics characters for values from 0 to 127 . III) EXTENDED ASCII: Extended ASCII is an eight-bi t code that specifies the characters for values from 12 8 to 255. The first 40 symbols represent pronunciation and special punctuation. The remaining symbols are graphic symbols. IV) UNICODE. The Unicode Worldwide Character Standard provides up to four bytes—32 bits—to represent each letter; number, or symbol. Unicode codes can be created to represent more than 4 billion different characters or symbols with four bytes. This total is enough for every unique character and symbol in the world, including the vast Chinese, Korean, and Japanese character sets and t hose found in known classical and historical texts. In addition to world letters, special mathematical and scientific symbols are represented in Unicode. One major advantage that Unicode has over other text code systems is its compatibility with ASCII codes. he first 256 codes in Unicode are identical to the 256 codes used by the ASCII and Extended ASCII systems.

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1 COMPUTER COURSE  HOW PROCESS THE DATA IN COMPUTER?

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Processing is the thinking that the computer does - the calculations, comparisons, and decisions. Computers process very large amounts of data because they can communicate the data much more quickly than a person. Most data processing is mundane, and would be prone to human error if not processed by computer. The processing can be done in computer at two places. They are • • CPU MEMORY

1. CPU :( Central Processing Unit ) The CPU, or Central Processing Unit, is the part of the computer where work gets done. In most computers, there is one processing chip. CPU performance is often measured in millions of instructions per second (MIPS). Newer CPUs can be measured in billions of instructions per second (BIPS). CPU has two parts called CONTROL UNIT and ALU. Control Unit: The control unit is responsible for controlling the transfer of data and instructions among other units of a computer. It is considered as the “central nervous system” of a computer as it manages and coordinates all the units of computer. It also performs the physical data transfer between memory and hardware devices. DR C.S.N DEGREE & P.G COLLEGE BHIMAVARAM 31

1 COMPUTER COURSE Arithmetic logic unit (ALU):

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ALU stands for Arithmetic/Logic Unit. This is the part that executes the computer's commands. A command must be either a basic arithmetic operation or one of the logical comparisons. Operations Performed by the Arithmetic Logic Unit (Arithmetic Operations) + * % Add Subtract Multiply Divide Rise by a power The ALU includes a group of registers with high-speed memory locations built directly into the CPU that are used to hold the data currently being processed. You can think of the register as a scratchpad. The ALU w ill use the register to hold the data currently being used for a calculation. For the data processing and execution CPU can take four steps: 1. Fetching: Before the CPU can execute an instruction, the control unit must retrieve (or fetch) a command or data from the computer’s memory. 2. Decoding: Before a command can be executed, the control unit must break down (or decode) the command into instruct ions that correspond to those in the CPU’s instruction set. 3. Executing: When the command is executed, the CPU carries out the instructions in order by converting them into microcode. 4. Storing.: The CPU may be required to store the results of an instruction in memory (but this condition is not always required). (Logical Operations) =, # equal to, not equal to >, !> greater than, not greater than <, ! < (Less than, not less than

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2. Memory:
The CPU contains the basic instructions needed to operate the computer; but it cannot store entire programs or large set s of data permanently. The CPU needs to have millions (or even trillions) of bytes of space where it can quickly read or write programs and data while they are being used. This area is called memory, and it consists of chips either on the motherboard or on a small circuit board attached to the motherboard. There are three types of built-in memory: permanent, non-permanent and flash memory. I) Permanent or Non-volatile Memory: Some memory chips contain or stores the data even when the computer is turned off. This type of permanent memory is called nonvolatile. The data in t these chip is only read and used but it can not changed the data. so the memory is called read only memory (RO M ). The ROM contains a set of start-up instructions called the “Basic input output system” (BIOS) for a computer. BIOS contains another set of routines, this routine is called the “power on self test” (POST). The Rom’s can be divided into PROM, EPROM and EEPROM. II) Non-permanent or Volatile Memory: Volatile memory requires power to store data. The volatile memory in a computer is called “random access memory” (RAM). RAM's job is to hold programs and data while they are in use. RAM's lose the programs and data when the computer is switch-off. RAM consists of chips on a small circuit board. Single in-line memory modules (SIMMs) and dual in-line memory module (DIMM) chips are found in “desktop computers”. Small outline DIMM (SO-DIMM) chips are found in “laptop computers”. III) Flash Memory: Flash memory is a special type of nonvolatile memory. It is often used in portable digital devices for storage. Digital cameras, portable MP3 players, USB “ key chain" storage devices, and game consoles all use flash memory. The flash memory works by having actual switches store the binary values that make up the data. Thus, on a camera with a flash card, the picture is stored on the card by turning millions of tiny switches on and off. Barring catastrophic damage to the card, the picture is stored indefinitely. DR C.S.N DEGREE & P.G COLLEGE BHIMAVARAM 33

1 COMPUTER COURSE  WHAT IS BUS? WHAT ARE THE DIFFERENT TYPES OF BUS’S?

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The Bus:
“A bus is a path between the components of a computer” There are two main b uses in a computer: “Internal or system bus”. “External or expansion bus”. a. The system bus displayed on the motherboard and connects the CPU to other devices that reside on the motherboard. Cables from disk drives and other internal devices are plugged into the bus. b. An external bus connects external devices, such as the keyboard, mouse, modem, and printer and so on, to the CPU. c. The system bus has two parts: “The data bus” “The address bus”

The Data Bus:
The data bus is an electrical path that connects the CPU, memory and the other hardware devices on the motherboard. The bus is a group of parallel wires. The number of wires in the bus affects the speed at which data can travel between hardware components. Because each wire can transfer one bit of data at a time. An eight wire bus can move 8 bits at a time. A 16 bit bus can transfer 2 Bytes at a time A 32-bit bus can transfer 4 Bytes at a time. The new model computers have a 64-bit data bus called the Front Side Bus that transfers 8 Bytes at a time. The bus's speed is measured in megahertz (MHz). The majority of today’s PCs have a bus speed of either 100 MHz or 133 MHz, but higher speeds of bus is 800 MHz. DR C.S.N DEGREE & P.G COLLEGE BHIMAVARAM 34

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The Address Bus:
The address bus is a set of wires similar to the data bus. The address bus connects only the CPU and RAM and carries only memory addresses. Remember each byte in RAM is associated with a number, which is its memory address.

Categories of bus’s:
1. ISA bus: The Industry Standard Architecture (ISA) bus. It is a 16 -bit data bus. It became the de facto industry standard on its release in the mid-1980s and is still used in many computers to attach slower devices (such as modems and input devices) to the CPU. 2. The Local bus: The Local bus was developed to attach faster devices to the CPU. A local bus is an internal system bus that runs between components on the motherboard. Most system buses uses some type of local bus technology today and are coupled with one or more kinds of expansion bus. 3. PCI bus: The Peripheral Component Interconnect (PC I) bus. It is a type of local bus designed by Intel to make it easier to integrate new data types, such as audio, video, and graphics. 4. AGP bus: The Accelerated Graphics Port (AGP) bus. It is incorporates a special architecture that allows the video card to access the system’s RAM directly. It is increasing the speed of graphics performance. The AGP standard has led to the development of many types of accelerated video DR C.S.N DEGREE & P.G COLLEGE BHIMAVARAM 35

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cards that support 3-D and full- Motherboard motion video. While AGP improves graphics performance, it cannot be used with all PCs. 5. USB bus: The Universal Serial Bus (USB) is a relatively new bus found on all modern machines. Unlike the PCI and AGP, USB is a hot swappable bus. This means that a user can connect then disconnect a USB device without affecting the machine. USB supports up to 127 devices connected in either a daisy chain or hub layout. 6. IEEE 1394: IEEE 1394 (Fire W ire) ports were once found only on Macintosh computers, but they are now increasingly common in IBM-compatible PCs. FireWire is used to connect video devices such as cameras and video cameras. Many digital TV connections also use FireWire. 7. PC Card bus: The PC Card bus is used exclusively on laptop computers. Like USB, PC Card is hot swappable. A PC Card is about the size of a stack of four credit cards. Common uses for PC Card include WiFi cards, network cards, and external modems.

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MEMORY
WHAT IS MEMORY (OR) STORAGE DEVICE? (Or) WHAT ARE THE DIFFERENT TYPES OF STORAGE DEVICES? (Or) EXPLAIN ABOUT DIFFERENT TYPES OF MEMORYS? *Primary memory devices:
Definition: 1. Memory or storage capacity is one of the important components of a computer.

Any storage unit of a computer system is classified on the basis of the following criteria: Access time: This is the time required to locate and retrieve stored data from the storage unit in response to program instructions. 2. Storage capacity: It is the amount of data that can be stored in the storage unit. 3. Cost per bit of storage. The computer stores a character in the storage cells with binary (0,1) mechanism. Thus the basic unit of memory is a bit (binary digit 0, 1). To store a character in a computer requires 8 bits or 1 byte. This is called the word length of the storage unit. The different units of measurement are 8 Bits = 1 Byte 210 (or) 1024 Bytes = 1 Kilo Byte (KB) 210 KB (or) 1024 KB = 1 Mega Byte (MB) 210 MB (or) 1024 MB = 1 Gega Byte (GB) 210 GB
( or)

1024 GB = 1 Terra Byte (TB) 1.Primary memory (main memory) 2. Secondary memory

There are mainly two types of memories:

1. Primary memory (main memory): a. Primary memory is the one of the main memory of the computer. b. Primary memory is accessible directly by the central processing unit.

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c. In Primary memory the contents or data is lost as soon as if the computer is switched off. You can store and retrieve data much faster with primary memory. d. But the Primary memory is more expensive and size is less. e. It can stores the necessary programs of the system software for execute user programs. The main memory or primary memory can be divided into two types: a. RAM (Random Access Memory) b. ROM (Read Only Memory).

Random Access Memory (RAM):
a) RAM stands for Random Access Memory. b) It is possible to select randomly and use any location of the memory directly store and retrieve data. c) It is also called read or write memory. d) The data or instructions can be stored in the RAM is temporarily. e) In RAM data is disappears as soon as the power to the computer is switched off. f) So now we can say that RAM is volatile memory. g) This can be divided into 2 types: STATIC RAM and DYNAMIC RAM. h) In the static ram the data or instruction can stores only as long as the power supply is ON. i) But in the dynamic ram the information or data can be stored very short time and it refreshed periodically.

Read Only Memory (ROM):
a) ROM stands for Read only Memory. b) This can store the programs and data is permanently. c) The ROM stores some standard processing programs supplied by the manufacturers to operate the personal computer. d) The ROM can only be read by the CPU but it cannot be changed or write any data. e) It does not loose their content, data or instructions if the power supply is failure or supply off. f) ROM also called as non-volatile memory. g) This can be divided into 3 types: PROM, EPROM, EEPROM and FLASH ROM

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PROM (Programmable Read Only Memory) memories were developed at the end of the 70s by a company called “Texas Instruments”. These memories are chips comprising thousands of fuses or diodes that can be "burnt" using a device called a “ROM programmer", applying high voltage (12V) to the memory boxes to be marked. The fuses thus burnt correspond to 0 and the others to 1. EPROM: EPROM (Erasable Programmable Read Only Memory) memories are PROMs that can be deleted. These chips have a glass panel that lets ultra-violet rays through. When the chip is subjected to ultra-violet rays with a certain wavelength, the fuses are reconstituted, meaning that all the memory bits return to 1. This is why this type of PROM is called erasable. EEPROM: EEPROM (Electrically Erasable Read Only Memory) memories are also erasable PROMs, but unlike EPROM’s, they can be erased by a simple electric current, meaning that they can be erased even when they are in position in the computer. Flash ROM: Flash ROM is also called flash BIOS or flash memory. It is a type of constantly powered nonvolatile memory that can be erased and re-programmed in blocks. It is a variation of EEPROM, which is erased and rewritten at the byte level. Flash memory is often used to hold the control code such as the BIOS in a personal computer. When BIOS needs to be changed or rewritten, the flash memory can be written in block (rather than byte) sizes, thus making it easier to update.

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*SECONDARY STORAGE MEMORY DEVICES: The secondary storage devices where used to overcome the problems with primary memory. The Secondary Memory is also known as Auxiliary Memory or Backup Memory. These are divided into two types’ magnetic memory and optical memories. There are so many types of secondary memory devices: 1. Floppy Disks 2. Hard Disk (Local Disk) 3. CD-R, CD-RW, DVD-R, DVD-RW 4. Pen Drive 5. Zip Drive 6. Memory Cards 7. External Hard Disk MAGNETIC MEMORY DEVICES: 1. Floppy disk: a) It is also referred as “Diskette”, and is made of flexible “Vinyl material”. b) It has a small hole on one side called “Right protect notch”, which protects accidental writing/deleting the information from the disk. c) There is a hole in the centre through which the “spindle” of drive unit rotates the disk. d) The disks are available in two sizes of 5.25 and 3.5 inches and these could be either lowdensity or high-density floppies. e) Storage capacities of floppies are measured in kilobytes (KB) and megabytes (MB). f) The details about the storage capacities of the floppies are presented below:

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1 COMPUTER COURSE (a) (a) (a) (a) (a) (a) 51/4-inch floppy disk 2. Hard disk:

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a) The hard disk can hold more information than the floppy disk and the retrieval of information from hard disk is faster when compared to floppies or tapes. b) A hard disk is fixed inside the CPU and its capacity ranges from 20 MB onwards. c) The hard disk is made up of a collection of discs (one below the other) known as “platters” on which the data is recorded. d) These platters are coated with “magnetic material”. It is less sensitive to external environmental disorders and hence the storage in hard disk is safe. e) The hard disk rotates while recording data. This rotation speed is measured in the unit of revolutions per minute (rpm). The normal speed of hard disks is 3600 revolutions per second. f) The read/write head of the hard disks moves across its surface. g) A small hard disk might be as much as 25 times larger than a floppy disk. h) Storage Capacity of hard disks varies from 20 MB to several Gega bytes like 80GB, 160GB.

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*OPTICAL MEMORIE DEVICES: 3. CD-R, CD-RW, DVD-R, DVD-RW: (i) CD-R (Compact disc Recordable): Data can be written onto it just once. The stored data can be read. Data once written onto it cannot be erased. Its main advantage is that it is portable and can hold a large amount of data. (ii) CD-RW (Compact disc Rewritable): It is also called erasable CD. Data once written onto it can be erased to write or record new information many times. The storage capacity of most CD-ROMs is approximately 650 MB or 700 MB. CD-ROM: CD-ROM stands for Compact Disk–Read Only Memory iii) DVD (Digital Versatile Disc): DVD stands for Digital Versatile Disc. It is similar to a CD-ROM, except that it can store larger amounts of data. The storage capacity of a DVD is at least 4.7MB. DVDs that can store up to 17GBs are also available. Because of their capacity, DVDs are generally used to store a very large multimedia presentations and movies that combine high quality sound and graphics.

4. pen drive(Flash Drive): It is a small, portable device that can be used to store, access and transfer data. Due to its small size, it is commonly called Pen drive. It is also called USB drive. We can read, write, copy, delete, and move data from computer to pen drive or pen drive to computer. It comes in various storage capacities of 2GB, 4GB, 8GB etc.

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This device is plugged into the USB port of the computer and the computer automatically detects this device. 5. Zip drive: A zip drive is a device for reading and writing data from removable storage Devices called Zip discs. Internal models typically take up a 2.5" drive bay (like a floppy disk drive). External models are about the size of a thick paperback book. A zip disk is about the size of 3 3.5" floppy disks stuck back to back, but has significantly larger capacity. Zip disks are now, like floppy disks, obsolete. They are physically larger, more expensive, slower, store less data and are less reliable then USB memory sticks. 6. Memory cards: A memory card or flash card is an electronic flash memory data storage device used for storing digital information. They are commonly used in many electronic devices, including digital cameras, mobile phones, laptop computers, MP3 players and video game consoles. They are small, re-recordable, and able to retain data without power. 7. External Hard disk: A hard drive that is outside of the computer case in its own enclosure. Most external hard drives support the IDE interface and are slightly bigger than a hard drive itself. When purchasing an external hard drive you can buy a full external hard drive system that consists of both the hard drive and the enclosure, or you can purchase just the enclosure to hold your own hard drive.

*Solid-State Storage Devices:
Solid state storage devices are unique, among today’s storage devices because they do not use disks or tapes and have no moving parts. Solid-state storage is either magnetic or optical. Instead, it relies on integrated circuits to hold data. Some solid-state storage devices are nonvolatile: means they can retain their data even when the system’s power is turned off. Others are volatile: means they require a constant supply of electricity or they will lose their data. The device’s volatility depends on the type of memory circuits it uses. They are divided into fallowing types: DR C.S.N DEGREE & P.G COLLEGE BHIMAVARAM 43

1 COMPUTER COURSE 1. Flash Memory 2. Smart Cards 3. Solid State Disks

k.suresh

1. Flash Memory: Flash memory is a special type of memory chip that combines the features of RA M and ROM. user or program access data randomly in flash memory and over write any or all of its contents at any time. Flash memory is nonvolatile memory, so data is retained even when power is off. Flash is commonly used in digital cameras and multimedia players’ i.e. M P3 players. These devices usually connect to a computer’s USB or FireWire port and can store 256 MB or more of data. 2. Smart Cards: Smart cord is a device with extraordinary potential and looks like an ordinary credit card. Smart cards contain a small chip that stores data. The user can read data from the card, add new data, or revise existing data from smart card using a special device called a smart card reader. Some smart cards, called “intelligent smart card”, also contain their own tiny microprocessor; and they function like a computer. 3. Solid State Disks: A solid-state disk (SSD) is not a disk at all. This device uses very last memory chips, such as synchronous dynamic RAM (SDRAM ) to store data. SDRAM is much faster than standard RAM. Large-scale SSD systems can store a terabyte or more of data. An SSD may be a free-standing unit that connects to a server computer or a card that plugs into one of the server' s expansion slots.

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Software & languages
*What is software & types of software’s?
SOFTWARE: Software is a program or set of instructions that causes the Hardware to
function in a desired way. There are two types of software - system software and application/ utility software.

Application software: Application software allows end users to accomplish one or more specific (non-computer related) tasks. Typical applications include industrial automation, business software, educational software, medical software, databases, and computer games. Businesses are probably the biggest users of application software, but almost every field of human activity now uses some form of application software. It is used to automate all sorts of functions. System Software or utility software: System Software enables an application software to interact with the computer hardware. System software is the ‘background’ software that helps the computer to manage its internal resources. The most important system software is the operating system. The system software performs important tasks such as running the program, storing data, processing data etc. Windows XP is an example of system software.

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What is language and what are the different types of languages?

COMPUTER LANGUAGES: Language is the source of communication among human beings. Different countries/regions have different languages. Similarly, in order to communicate with the computer user also needs to have a language that should be understood by the computer. For this purpose, different languages are developed for performing different types of work on the computer. Basically, languages are divided into two categories according to their interpretation.

1. Low Level Languages:
Low level computer languages are machine codes or close to it. Computer cannot understand instructions given in high level languages or in English. It can only understand and execute instructions given in the form of machine language i.e. language of 0 and 1. There are two types of low level languages: Machine Language. DR C.S.N DEGREE & P.G COLLEGE BHIMAVARAM 46

1 COMPUTER COURSE Assembly Language

k.suresh

a) Machine Language: It is the lowest and most elementary level of Programming language and was the first type of programming language to be developed. Machine Language is basically the only language which computer can understand. In fact, a manufacturer designs a computer to obey just one Language, its machine code, which is represented inside the computer by a String of binary digits (bits) 0 and 1. The symbol 0 stands for the absence of Electric pulse and 1 for the presence of an electric pulse. Since a computer is Capable of recognizing electric signals, therefore, it understands machine Language. Advantages of Machine Language: i) It makes fast and efficient use of the computer. ii) It requires no translator to translate the code i.e. directly understood by the computer Disadvantages of Machine Language: i) All operation codes have to be remembered ii) All memory addresses have to be remembered. iii) It is hard to amend or find errors in a program written In the machine language iv) These languages are machine dependent i.e. a particular b) Assembly Language: It was developed to overcome some of the many inconveniences of machine language. This is another low level but a very important language in which operation codes and operands are given in the form of alphanumeric symbols instead of 0’s and l’s. These alphanumeric symbols will be known as mnemonic codes and can have maximum up to 5 letter combination e.g. ADD for addition, SUB for subtraction, START,LABEL etc. DR C.S.N DEGREE & P.G COLLEGE BHIMAVARAM 47

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Because of this feature it is also known as ‘Symbolic Programming Language’. This language is also very difficult and needs a lot of practice to master it because very small

2. High Level Languages
High level computer languages give formats close to English language and the purpose of developing h igh level languages is to enable people to write programs easily and in their own native language environment (English). High-level languages are basically symbolic languages that use English words and/or mathematical symbols rather than mnemonic codes. Each instruction in the high level language is translated into many machine language instructions thus showing one-to-many translation

Types of High Level Languages BASIC (Beginners All Purpose Symbolic Instruction Code). FORTRAN (Formula Translation). PL/I (Programming Language, Version 1). ALGOL (Algorithmic Language). APL (A Programming Language).

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NETWORKS
1Q) what is network? 2Q) what are the uses of networks? 3Q) what are the different types of networks? 4Q) what is topology? 5Q) what are the different types of topologies?

What is network?
A network is a set of technologies including hardware, software, and media that can be used to connect computers together, enabling them to communicate, exchange information, and share information. Networks allow many users to access shared data and programs almost instantly. When data and programs are stored on a network and are shared, individual users can substantially reduce the need for programs on their own computers.

What are the uses of networks?
1. Simultaneous Access: There are moments in any business when several workers may need to u se the same data at the same time. Without a network that allows workers to share files, workers must keep separate copies of data stored on different disks by each worker who accesses the data. When the data is modified on one computer, data on the other computers be comes outdated. It becomes difficult to determine which copy of the data is the most current. 2. Shared Peripheral Devices DR C.S.N DEGREE & P.G COLLEGE BHIMAVARAM 49

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The ability to share peripheral devices (especially expensive ones such as high volume laser printers, which can cost thousands of dollars) is one of the best reasons for small businesses to set up a network. Although printers are more affordable than they were a few years ago, it is still too expensive to provide every worker with a personal printer. Aside from the cost of buying multiple printers, maintenance contracts and supplies increase the total cost of ownership. When several people can share a printer on a network, printing becomes less expensive and easier to manage. 3. Personal Communications: One of the most far-reaching applications of personal data communications is electronic mail (e-mail), a system for exchanging written messages (and, increasingly, voice and video messages) through a network. a) Video conferencing: Video conferencing enables real-time communication over a distance by allowing people at two or more sites to communicate with each other by seeing a video picture of the people at the other sites. Each site has one or more cameras, microphones, loudspeakers, and monitors, as well as a CODEC (compressor/de-compressor), which processes the audio and video. b) Audio-conferencing: Audio-conferencing provides an audio link similar to that of a conventional telephone, except that it offers much higher-quality audio and enables more than two sites to be linked together: Using hands-free audio units with sensitive microphones and sophisticated echo-cancellation software. Audio-conferencing enables communication between groups of participants. c) Data-conferencing: Data conferencing enables participants at two or more sites to have a shared workspace on their computer desktops. This might be a shared “white board”. where they can draw, write, or import and manipulate images collaboratively in real time. Or it might be "application sharing," where a piece of software can be run and controlled by both users. 4. Easier Data Backup: In business, data is extremely valuable, so it is important that employees back up their data. One way to assure that data is backed up is to keep it on a shared storage device that employees can access through a network. Often the network manager makes regular backups of the data on the shared storage device. Managers also can use special software to back up files stored on employees' hard drives from a central location. DR C.S.N DEGREE & P.G COLLEGE BHIMAVARAM 50

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What are the different types of networks?
There are three main types of networks: 1. Local area networks (LANs) 2. Wide area networks (WANs). 3. Metropolitan area networks (MANs) Local area networks (LANs): A local area network (LAN) is a data communication system consisting of several devices such as computers and printers. This type of network contains computers that are physically connected using cables, infrared links, or wireless media. A LAN can consist of just two or three PCs connected together to share resources. A local area network (LAN) is a computer network covering a small physical area, like a home, office, or small group of buildings, such as a school, or an airport.

Wide area networks (WANs): Wide area network (WAN) is two or more LANs connected together, generally across a wide geographical area. Wide Area Network (WAN) is a computer network that covers a broad DR C.S.N DEGREE & P.G COLLEGE 51 BHIMAVARAM

1 COMPUTER COURSE area In personal (PANs), (LANs), networks

k.suresh
contrast with area networks local area networks campus area (CANs), or metropolitan area

networks (MANs) which are usually limited to a room, building, campus or specific metropolitan area (e.g., a city) respectively. The largest and most well-known example of a WAN is the Internet.

Metropolitan area networks (MANs): The metropolitan area network (MAN) is a large scale network that connects multiple corporate LANs together. MANs usually are not owned by a single organization; their communication devices and equipment are usually maintained by a group or single network provider that sells its networking services to corporate customers. MANs often take the role of a high speed network that allows for the sharing of regional resources. MANs also can provide a shared connection to other networks using a WAN link.

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What is topology?
TOPOLOGY is the physical layout of the workstations, severs, gateways, hubs and cabling, configuration of network, including the types of cable and connectivity devices used. Types of topologies: There are 6 types of topologies and are as follows. 1. Bus Topology, 2. Ring Topology, 3. Star Topology, 4. Mesh Topology, 5. Tree Topology. Bus Topology: 1. All the nodes (file server, workstations, and peripherals) on a bus topology are connected by one single cable. 2. A bus topology consists of a main run of cable with a terminator at each end. All nodes (file server, workstations, and peripherals) are connected to the linear cable. 3. Popular on LANs because they are inexpensive and easy to install.

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Ring Topology: 1. In a ring network, every device has exactly two neighbors for communication purposes. 2. All messages travel through a ring in the same direction. 3. A failure in any cable or device breaks the loop and can take down the entire network. 4. To implement a ring network we use the Token Ring technology 5. A token, or small data packet, is continuously passed around the network. When a device needs to transmit, it reserves the token for the next trip around, and then attaches its data packet to it.

Star Topology: 1. In a star network, each node (file server, workstations, and peripherals) is connected to a central device called a hub. 2. The hub takes a signal that comes from any node and passes it along to all the other nodes in the network. DR C.S.N DEGREE & P.G COLLEGE BHIMAVARAM 54

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3. Data on a star network passes through the hub, switch, or concentrator before continuing to its destination. 4. The hub, switch, or concentrator manages and controls all functions of the network. 5. The star topology reduces the chance of network failure by connecting all of the systems to a central node.

Mesh Topology: 1. In this topology, each node is connected to every other node in the network. 2. Implementing the mesh topology is expensive and difficult. 3. In this type of network, each node may send message to destination through multiple paths. 4. While the data is traveling on the Mesh Network it is automatically configured to reach the destination by taking the shortest route which means the least number of hops.

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1 COMPUTER COURSE Tree Topology:

k.suresh

1. A tree topology (hierarchical topology) can be viewed as a collection of star networks arranged in a hierarchy. 2. This tree has individual peripheral nodes which are required to transmit to and receive from one other only and are not required to act as repeaters or regenerators. 3. The tree topology arranges links and nodes into distinct hierarchies in order to allow greater control and easier troubleshooting. 4. This is particularly helpful for colleges, universities and schools so that each of the connect to the big network in some way.

DATA COMMUNICATIONS
Data communication: Data communications are the exchange of data between two devices via some form of transmission medium such as a wire cable. For data communications to occur, the communicating devices must be part of a communication system made up of a combination of hardware (physical equipment) and software (programs). The effectiveness of a data communications system depends on four fundamental characteristics: delivery, accuracy, timeliness, and jitter. 1. Delivery. The system must deliver data to the correct destination. Data must be received by the intended device or user and only by that device or user. 2. Accuracy. The system must deliver the data accurately. Data that have been altered in transmission and left uncorrected are unusable. DR C.S.N DEGREE & P.G COLLEGE BHIMAVARAM 56

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3. Timeliness. The system must deliver data in a timely manner. Data delivered late are useless. In the case of video and audio, timely delivery means delivering data as they are produced, in the same order that they are produced, and without significant delay. This kind of delivery is called real-time transmission. 4. Jitter. Jitter refers to the variation in the packet arrival time. It is the uneven delay in the delivery of audio or video packets. For example, let us assume that video packets are sent every 3D ms. If some of the packets arrive with 3D-ms delay and others with 4D-ms delay, an uneven quality in the video is the result *WHAT ARE THA PHYSICAL COMMUNICATION MEDIA?

Twisted-pair cable
A cable made by intertwining two separate insulated wires together. There are two twisted pair types. Shielded and Unshielded. Shielded Twisted Pair (STP) has a fine wire mesh surrounding the wires to protect the transmission; Unshielded Twisted Pair (UTP) does not. Shielded cable is used in older telephone networks, network, and data communications to reduce outside interference..

Coaxial
A cable

cable:
that is used in

video, communications, and audio. This cable has high bandwidths and greater transmission capacity. Most users relate to a coaxial or coax cable as a cable used to connect their TVs to a cable TV service. However, these cables are also used in networks and what allow a broadband cable Internet connection using a cable modem. In the picture to the right, is an example of a coaxial cable. As can be seen in this picture, the cable is a thick cable with a metal male connector end that is screwed onto a female connector.

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Fiber-optic cable:
Fiber-optic cables are hollow cables that send data by pulses of light. Fiber optics allows for a much faster data transmission because of the capability of transmitting data at the speed of light. Most home computer users will never get the opportunity to work with fiber-optic cables because almost all home networks use other cables or wireless connections to connect their computers together. Fiber-optic cables are most often used in corporate networks or worldwide networks such as Internet backbones because of the capabilities of the cable.

*Operating System*
Definition:
An Operating system is a program that controls the execution of application programs and acts as an interface between the user of a computer and the computer hardware.

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History of Operating System:

Functions of Operating System:
Today most operating systems perform the following important functions: 1. Processor management: It manages the assignment of processor to different tasks being Performed by the computer system. 2. Memory management: It manages the allocation of main memory and other storage areas to the system programs’ as well as user programs’ and data. 3. Input / Output management: It manages the co-ordination and assignment of different Input and Output devices while one or more programs are executed .4. File management: It allows all files to be easily changed and modified through the use of text editors or some other file manipulation routines. 5. Establishment and enforcement of a priority system : It determines and maintains the order in which jobs are to be executed in the computer system. 6. Interpretation of commands and instructions. DR C.S.N DEGREE & P.G COLLEGE BHIMAVARAM 59

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7. Facilitates easy communication between the computer system and the computer operator.

Types of operating system:
1. Batch Operating System 2. Real-Time Operating System (RTOS) 3. Single User, Single Task 4. Single User, Multitasking 5. Multi-user 6. Distributed Operating System 1. Batch Operating System: In a batch processing operating system interaction between the user and processor is limited or there is no interaction at all during the execution of work. Data and programs that need to be processed are bundled and collected as a ‘batch’ and executed together. Batch processing operating systems are ideal in situations where: a) There are large amounts of data to be processed. b) Similar data needs to be processed. c) Similar processing is involved when executing the data. The system is capable of identifying times when the processor is idle at which time ‘batches’ maybe processed. Processing is all performed automatically without any user intervention.

2. Real-Time Operating System (RTOS) Real-time operating systems are used to control machinery, scientific instruments and industrial systems such as embedded systems (programmable thermostats, household appliance controllers), industrial robots, spacecraft, industrial control (manufacturing, production, power generation, fabrication, and refining), and scientific research equipment. An RTOS typically has very little user-interface capability, and no end-user utilities, since the system will be a "sealed box" when delivered for use. A very important part of an

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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. An early example of a large-scale real-time operating system was Transaction Processing Facility. Current users include Sabre (reservations), Amadeus (reservations), VISA Inc (authorizations), Holiday Inn (central reservations), CBOE (order routing), Singapore Airlines, KLM, Qantas, Amtrak, Marriott International , Worldspan and the NYPD (911 system). 3. Single User, Single Task: This operating system is designed to manage the computer, so that one user can effectively do one computer at a time. The Palm OS for Palm handheld computers is a good example of a modern single-user, single-task operating system. 4. Single User, Multitasking: This is the type of operating system most people use on their desktop and laptop computers today. Microsoft's Windows and Apple's Mac OS platforms are both examples of operating systems. In that a single user has multiple or several programs in operation at the same time. For example, it's entirely possible for a Windows user to be writing a note in a word processor while downloading a file from the Internet while printing the text of an e-mail message.

5. Multi-user: Multi-user is a term that defines an operating system or application software that allows concurrent or continues access by multiple users of a computer. A multi-user operating system allows many different users to take advantage of the computer's resources simultaneously. Unix, VMS and mainframe operating systems, such as MVS, are examples of multi-user operating systems. Time-sharing systems are multi-user systems. Most batch processing systems for mainframe computers may also be considered "multi-user", to avoid leaving the CPU idle DR C.S.N DEGREE & P.G COLLEGE 61 BHIMAVARAM

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while it waits for I/O operations to complete. However, the term "multitasking" is more common in this context.

6. Distributed Operating System: In a distributed system, software and data maybe distributed around the system, programs and files maybe stored on different storage devices which are located in different geographical locations and maybe accessed from different computer terminals. While we are mostly accustomed to seeing multi-tasking and multi-user operating systems, the other operating systems are usually used in companies and firms to power special systems.

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