Computer VI - CHAPTER 1.docx

**Introduction** A computer is an electronic device that accepts data from the user, processes it and gives the desired output. It is a machine capable of performing calculations with the help of a mechanical computing device The evolution of computers started back in the late 1930s. Computers at t...

**Introduction** A computer is an electronic device that accepts data from the user, processes it and gives the desired output. It is a machine capable of performing calculations with the help of a mechanical computing device The evolution of computers started back in the late 1930s. Computers at that time used only binary language for their operations. **Early Calculating Devices** A few calculating devices used prior to the development of computers are discussed here. The abacus, the first calculating machine, was developed in China. It was used to count numbers and perform simple calculations such as addition and subtraction. **Napier\'s Bones** Napier\'s Bones was developed by Sir John Napier and released in 1617. The device was used to perform calculations involving addition, subtraction, multiplication and division. It was named so because the numbers were carved on bones or strips of wood **Pascaline** The Pascaline, one of the first mechanical calculators, was invented by Blaise Pascal in the year 1642. Although it could perform only addition and subtraction, it still became very popular. **Difference Engine** The Difference Engine was designed by Charles Babbage in the year 1822. It was an early digital device which could perform mathematical and astronomical calculations. It was also capable of storing data temporarily and printing the output. **Analytical Engine** The Analytical Engine was designed by Charles Babbage in the year 1837. It was the first mechanical general purpose computer which followed a typical IPO cycle used i modern computers. The machine took input using a reader as an input device. It was made up of \'mill\', the calculating unit like the CPU in modern computers. **Evolution of Computers** From everyday tasks to moving satellites in space, computers have revolutionised almost everything in our society. The development of computers has been classified into generations. You will now learn more about these. **First generation computers (1940-1956) - vacuum tube** In the evolution of computers, the first generation was characterised by the use of vacuum tubes. The first generation computers were built to solve physics equation using electronic vacuum tubes as switching components. These used machine language. A machine language is a low-level programming fanguage and is written using long strings of Os and Is for comparing Machine language varies with the computer used. The first generation computers were expensive and bulky The vacuum tubes did not support multitasking Programs written in machine language were complicated and difficult to remember The Universal Automatic Computer (UNIVAC) and Electronic Numerical Integrator and Computer (ENIAC) are examples of first generation computing devices. The UNIVAC was the first commercial computer **Second generation computers (1956-1963)-transistor** In the 1960s, transistor-based computers replaced vacuum tubes which marked the second generation of computers. Transistors made computers smaller and cheaper They also made computers energy- efficient, but the transistors were subject to damage because of the emission of large amounts of heat from the computer Computers belonging to this generation used punched cards for input. They used assembly language, which is a low-level programming language. This language is based on the English alphabet. The instructions are written in the form of codes. The assembly language was machine dependent, and had to be written based on the configurations of the computer Microcomputer Microcomputer was a commonly used term for personal computers. A personal computer assemblage consists of a CPU, Fifth generationmatters computer memory (primary and secondary) and various input and output devices. Only one person can use it at a time. It is much slower and has less storage capacity than a minicomputer or a mainframe computer It is commonly used in classrooms, homes, banks, universities, etc. There are various kinds of microcomputers available. These are shown below. Desktop PC: A microcomputer designed to fit comfortably on top of a desk, typically with the monitor in front and the system unit on the side. Laptop: A portable microcomputer You can use it on your lap. Laptop computers are also called notebook computers. Laptop Tablet: A mobile computer. It offers users a touchscreen environment that may or may not be accompanied by a stylus (a pointing device). They are available in a variety of sizes and have a built-in/virtual keyboard. Mainframe computer Mainframe compsters are very large, often filling an entire room. They can store an enormous amount of information, and perform many tasks simultaneously. They can comtnunicate with many users at the same time and are very expensive Mainframe computers usually have several terminals connected to them. These terminals look like small computers but are only used for sending and recerving information from the mam computer Terminals can be located either in the same room with the mainframe computer, or they can be in different rooms, buildings, cities, etc. Large businesses, government agencies, banks and universities usually use mainframe computers. Big hospitals, airline reservation companies and many other large businesses prefer mainframe computers because of their capability of processing enormous amounts of data. Mainframe computers Minicomputer A minicomputer is much larger than a microcomputer and much more expensive. It lies between microcomputers and mainframe computers and is often referred to as a midrange computer It possesses most of the features found on a mainframe computer, but on a limited scale. It can still have many terminals, but not as many as the mainframe. It can store a large amount of information. but not usually as much as the mainframe computers. It uses an enhanced instruction which can support scientific processing and commercial applications. Medium and small businesses and colleges typically use minicomputers. Supercomputer DEC PDP-8 minicomputer Supercomputers are one of the many types of modern computing machines, which are big, powerful and capable of doing very speedy calculations. It is because of theirhigh-speed processing ability that supercomputer systems are used in graphic animation, weather forecasting, nuclear research works, petroleum research, crypt analysis, molecular modelling, etc The difference between the mainframes and supercomputers is that while mainframe machines are primarily used for a number of purposes, supercomputers are designed to serve a single purpose. Supercomputer Functional Components of a Computer The functional components of a computer are shown in the diagram below Functional components of a computer Input Unit ---\> Central Processing Unit (CPU) ---\--\> Output Unit The input and output units attached to a computer are called computer peripherals. Input unit Data is accepted by a computer through the input unit connected to it. The standard input device is a keyboard. Examples of other input devices are joysticks, mice, web cameras, Magnetic Ink Character Recognition Readers (MICR), Optical Mark Recognition Readers (OMR), Optical Character Readers (OCR), touchscreens, smart card readers, digital readers, etc You have already read about some of the commonly used input devices in carter hos Some other input devices are described below. Bar code reader: This is used by a computer to scan and identity the product or item codes in supermarkets, book stores, and many other places. The code for each item, such as the price code, item code, etc, is a unique combination of vertical bars and can be identified by a bar code reader. FACT FILE Quick Response (QR) codes are special harcodes that can be read using QR reading devices, mainly installed as an application on smartphones. These codes link the user directly to text, emails or websites Magnetic Ink Character Recognition (MICR) Reader This reads the special characters printed using a special magnetic imk. Cheque number, bank code and branch code are printed on cheques using magnetic ink, making them difficult to forge. The MICRs scan this information and are therefore capable of sorting cheques Magnetic Ink Character Real Optical Mark Recognition (OMR) reader: Use for recognising a pre-specified space on a paper that is marked by a pencil or pen. It is commonly used for marking the answers on examination sheets. An OMR sheet Central Processing Unit The Central Processing Unit (CPU) is the control centre of a computer. It guides, directs and governs its performance. It is known as the brain of the computer. The CPU has three components which are responsible for different functions. These are discussed here. Arithmetic Logic Unit (ALU) The ALU performs all arithmetic and logical operations within a computer. This part provides the arithmetic and decision-making capability to a computer Control Unit (CU) The CU controls and guides the interpretation, flow and manipulation of all data and information. The CU sends control signals until the required operations are completed by the ALU and the memory. Another important function of the CU is program execution, that is, carrying out all the instructions stored in the program. The control unit even controls the flow of data from the input devices to memory and from memory to the output devices. Memory Unit (MU) The MU is that part of the computer where the data is stored and is accessible to the CPU. The various measurement units of computer memory are given here. 1\. Bit: A bit means a binary digit, that is, there are only two possibilities for each digit, either 0 or 1. A bit is an elementary unit of computer memory A number of bits when combined together in different ways are used for storing data in a computer. 2\. Byte: A group of 8 bits is called a byte. One byte is the smallest unit which can represent a meaningful data item or character in a computer. Memory is generally measured in terms of bytes. 3\. Nibble: A group of 4 bits is called a nibble The computer memory can also be expressed in other units and their interrelationship is given below 1 Byte 8 Bits 1024 Bytes 1024 Kilobyte (KB) 1 Kilobyte (KB) 1 Megabyte (MB) 1024 Megabyte (MB) 1 Gigabyte (GB) 1024 Gigabyte (GB) 1 Terabyte (TB) 1024 Terabyte (TB) 1 Petabyte (PB) 1024 Petabyte (PB) = 1 Exabyte (EB) 1024 Exabyte (EB) = 1 Zettabyte (ZB) 1024 Zettabyte (ZB)= 1 Yottabyte (YB) FACT FILE 1 kilobyte is equal to 1024 bytes and not 1000 bytes as it is 2 raised to the power 10 Primary memory Primary memory is the basic requirement of a computer. It determines the size and number of software applications that a computer can store. Primary memory stores t types of programs: system software and application software. You will learn more about them later in this chapter Primary memory limits the amount of data that a computer can process. The CPU can use this memory directly while processing information. On the basis of volatility of storage of data, primary memory is classified into volatile memory (RAM) and non- volatile memory (ROM) as shown in the table below Differences between RAM and ROM Random Access Memory (RAM) 1 Temporary memory 2\. Volatile in nature, that is, the information stored in RAM is designed to clear when the computer is turned off. 3\. The main internal storage area that a computer uses to run programs and store data. It is also called read/write memory Read Only Memory (ROM) 1\. Permanent memory. 2\. Non-volatile memory, that is, the information stored in ROM is retained even when the computer is turned off. 3 Built-in computer memory that can be read by a computer but cannot be modified. It is a memory unit that can only be read by a computer but cannot be modified. It is a memory unit that can only be read. Secondary memory is also known as auxiliary memory. It is used for storing data or programs on a temporary or permanent basis. The secondary memory is available in the form of storage devices. For example, hard disks, compact disks (CDs), flash drives, etc. The CPU cannot access secondary memory directly while processing information. The data is transferred to the primary memory when required. The computer uses its input and output devices to access data stored in the secondary memory. FACT FILE Cache memory can be used for increasing the capacity of the primary memory and to make the processing faster Output unit The Output Unit is for getting information from a computer. For example, the Visual Display Unit (VDU) or the monitor is an output device that displays the information on the screen. The information shown on a display unit is called a soft copy Speakers are the output devices which produce output in the form of audio. You can also obtain information from a computer on a physical medium, such as paper, with the help of a printer. Printed information is called a hard copy Other output devices are described below. Liquid Crystal Display (LCD) projector: Output from a computer can also be viewed on a large screen or flat surfaces other than the monitor using an LCD projector It is usually used for showing PowerPoint presentations in schools and businesses LCD projector Plotters. These are the output devices used for making high-quality graphics, charts. diagrams, maps, etc. Plotters use an ink jet or ink pens to create the required output on paper. There are different types of plotter available. The three basic types of plotter are. 1\. Inkjet plotter This sprays small droplets of ink onto a piece of paper and creates an image. 2 Flatbed plotter The pen or the inkjet moves in horizontal and vertical directво over a fixed horizontal flat surface on which paper is mounted. 3\. Drum plotter This uses a drum revolver or roller to move theated over de pe Dru plotter This is dating process. The paper is placed on which is then rotated. The pen is moved along the horizontal print the output. directions Categorisation of Software Software is a set of programs that runs a computer system Computer software is stored and executed (run) with the help of computer hardware. Major categories of software that form part of a computer system are discussed here FACT FILE Computers work on the theory of GIGO (Garbage In Garbage Out). It means that wrong input will give the wrong output. System software System software is a program that manages and supports the resources and operations of a computer system while it executes various tasks such as the processing of data and information, controlling the hardware components and allowing users to use the application software. In other words, system software is a bridge between the computer system bardware and the application software. An Operating System (OS) is an example of system software System software controls the internal computer operations. It can be further classified into two categories. Point of communication between two systems, devices Operating System (OS) An operating system is software which acts as an interface between the user and the computer (that is, all computer resources). It is an important component that controls all other components of the computer system Without an operating system, a computer will not work. Some of the most commonly used operating systems are Windows, DOS, UNIX, etc. Language translators: These are used to translate programming languages. There are three types of language translators Compiler: Translates the high-level language program into machine language. It converts the entire program in one go and reports all the program errors along with their line numbers. For example, C language uses a compiler. The translated program is called the object program or the object code. Interpreter Translates a program written in high-level language into machine language by converting and executing it line by line. If there is an error in any line, the interpreter reports it immediately and the program cannot continue until it is fixed. However, it is a smaller program than a compiler. For example, BASIC uses an interpreter as the translator Assembler: A language translator that converts a program written in assembly language into machine language. Application software Application software is a set of programs necessary to carry out operations for a specified application. These are the programs written by programmers to enable computers to perform a specific task. Various application software and their examples are given below. Application Software MS Word MS PowerPoint Spreadsheet package MS Excel. Lotus 123 Database management system MS Access, Sybase Business software Inventory management, payroll system, financial accounting, hotel management, etc. Image/video editing GIMP, Photoshop, Windows Movie Maker, elc Utility software Utilities are application programs which assist a computer by performing housekeeping functions like backing up disks, or scanning/cleaning viruses or arranging information. They ensure the smooth functioning of a computer. FACT FILE Some important utilities are the text editor used for creating and editing text files The open source application software provides the source code along with the exe file so that users can make changes in the code to suit their requirements. The open source substitute of MS Office is OpenOffice ⚫ backup utility that facilitates the backing-up of disks compression utility that facilitates compression of files  disk defragmentation utility that attempts to minimise the fragmentation on the disk ⚫ and anti-virus software that ensures a virus-free environment. GLOSSARY Abacus The first calculating machine that performed simple arithmetic calculations. Analytical engine The first mechanical general purpose computer which follows the typical IPO cycle used in modern day computers. Application software A set of programs necessary to carry out operations for a specified application. Assembler Converts a program written in assembly language into machine Assembly language A low-level programming language which uses English words. Bit A binary digit Byte A group of eight bits. Compiler A language translator that translates high-level language programs into machine language. Desktop A computer designed to fit comfortably on the top of a desk. Difference engine An early digital device which was designed to perform mathematical and astronomical calculations. Desktop computer A computer designed to fit comfortably on the top of a desk. High-level language A language that uses the english alphabet and mathematical symbols and on which the third generation of computers are based Interpreter A language processor which converts high-level language programs into machine language by converting and executing it line by line Laptop A portable computer that can be placed on your lap. Machine language A language written asing long strings of Os and is for computing. Mainframe computer A very large computer, often filling an entire room. Microcomputer A commonly used term for personal computers. Minicomputer A much larger than a microcomputer, and is also much more expensive, Napier\'s Bones An early device used for performing simple arithmetic calculations. Nibble A group of 4 bits, Operating system A software that acts as an interface between the user and the computer. Pascaline One of the first mechanical calculators to be developed. Primary memory Determines the size and number of software that a computer can store. Secondary memory The memory used for storing data or programs on a temporary or on a permanent basis. Smartphone A mobile phone built on a mobile OS with enhanced features compared an ordinary mobile phone. Source program A program written in a high-level language. Supercomputer A modern computing machine that is capable of giving speedy calculation The software that controls the internal computer operations. System software A mobile computer with a touchscreen and a built in virtual keyboard. A set of application programs that assist the computer by performing housekeeping functions. Tablet A mobile computer with a touchscreen and a built in virtual keyboard. Utility Softwares: A set of application programs that assist the computer by performing housekeeping functions. Chapter 2 : Operating System Introduction Computers cannot function on their own. They require programming instructions to work and manage the system. This job is done by an operating system. An operating system is a system software. It is the interface between the user and the computer. It performs the basic tasks of a computer. These are given below 1\. It recognises input from the keyboard. 2\. It sends output to the display screen. 3\. It keeps track of files and directories on the disk. 4\. It controls the peripheral (input and output) devices such as printers. 5\. It acts as an interface between the hardware of a computer and the user Some of the commonly used operating systems are Disk Operating System (DOS), MS Windows, Linux, Windows NT and Mac OS Booting Booting is a process that starts the operating system when the user turns on a computer. It is a self-starting process. Types of booting There are two types of booting: Warm Boot: Pressing the Restart button while the computer is already on. Cold Boot: Pressing the Power button when the computer is switched off. The booting process When you switch on a computer, the operating system is loaded into RAM automatically It follows the sequence given below. These steps are part of the booting process. 1\. As soon as the computer is turned on, the Basic Input/Output System (BIOS) is ru This software is built into a computer\'s ROM BIOS starts the operating system and supports the transfer of information between hardware devices. 2\. BIOS first conducts a Power-On Self Test (POST) to make sure all the components of the computer are working with a proper power supply. The BIOS then looks for the special boot programs that will load the operating system from the hard disk. 3\. A computer may have several disks or drives. The operating system is loaded in one of the disks. BIOS first looks for a floppy disk on drive A. If there is no system disk in it (where the operating system is loaded), BIOS then looks for the system files at a specific place on your hard disk. 4\. BIOS next looks at the first sector of the hard disk, and copies the information fron there to specific locations in RAM. This information is known as the Boot Record or Master Boot Record (MBR). 5\. The MBR program now loads the system files of the operating system into the RAM Once the system files are loaded, the OS is ready to take control of the system. OS remains in the computer\'s memory until the power is on. FACT FILE The technology that is different from its previous type is called a version. The various versions of Windows are Windows 95, Windows 98, Windows 2000 Windows ME, Windows NT, Windows XP, Windows Vista, Windows 7, Windows 8 and Windows 10 Let us now observe the booting process as shown in the flowchart below Computer is switched on ---\> BIOS conducts POST ----\> BIOS checks drives for System disk ---\> BIOS loads MBR ---\--\> MBR program loads operating system files Flowchart showing the process of booting Functions of an Operating System An operating system does the job of a system manager. It performs various important functions as shown in the diagram below Functions of an operating system Process Management Device Management Memory Management File Management Housekeeping Various functions of an operating system Process management An operating system controls and schedules the processes for execution by the CPU It is responsible for allocating the CPU\'s time to each process. For example, when you are working on an MS Word document it may cause several other background processes to begin, such as virus checks, memory management, etc After a job is done or a process is completed, the CPU becomes idle. After that, if there are other processes in queue, then the time is allocated to each process of the CPU This whole system is managed to ensure maximum output from the system. Process III ---\-\-\-\-\-- Process 11 ---\-\-\-\-\-\-\-- Process 1---\-\-\-\-\-\-\-\-\-\-\-\-\-\-- CPU Device management Device management is an important function of an operating system. It coordinates and controls the various input and output devices attached to the system. When the system is ready to take input, the input device is made available to the user, and when the processing job is over, the output is redirected to the output device. FACT FILE The operating system needs a software, called a device driver. This recognises the input and the output devices attached to the computer Memory management Whenever you start any application software, it gets loaded onto the system memory When you open any file, a copy of that file is loaded onto the memory from the disk This is done by an operating system. It allocates certain memory for other aff with the help of the booting process and sets aside the remaining memory for other application programs. File management A lot of data is stored on the hard disk. The hard disk is formed of millions of tracks and sectors. At the time of storing data on the disk, it is not compulsory that it occupies the sectors in a sequence. It is the job of an operating system to read the data from different tracks and sectors when required, and to store it in the available space Housekeeping Housekeeping includes all the services necessary to ensure the smooth operation of the computer system, like security, protection, resource accounting, back up, etc, Types of Operating System Single-user operating system As the name implies, a single-user operating system is designed so that only one user can work on a computer at a time. This is the type of operating system most people use on their desktops and laptops today, Windows, DOS and Mac OS are a few examples of a single-user operating system. Multi-user operating system A multi-user operating system supports multiple users at the same time and/or differem times. The operating system must make sure that the requirements of the different users are balanced. It must also ensure that each of the programs they are using has sufficient and separate resources so that a problem with one user does not affect the entire community of users. For example, Linux, Unix Windows NT and Novell Netware can support hundreds and thousands of networked users. Operating System Interface The operating system provides a platform on which the application program runs. It provides an interface which can be classified further. Character User Interface (CUI) In a CUI, the operating system provides an environment where the user needs to type a command to perform a particular action. For example, Disk Operating System (DOS). Graphical User Interface (GUI) In a GUI, the operating system provides a graphical environment where the mouse acts as a pointing device. The user can perform an action just by a mouse-click. For example, Windows operating system. Importance of Shut Down Windows remains in the computer memory until the power is on. When the computer is closed down, these operating system files are sent back to the hard disk so that no damage is caused to these files. This process is known as shut down of an operating system. If you switch off the computer without giving a proper shut down command then there is a high risk of losing the data, and it may also damage the Windows operating system. To shut down a computer properly click on the Start Shut down option. For other options, click on the arrow on the right of the Shut down option. It generally shows the following options: Switch user: Switches the user without closing the programs currently in use. Log off: Closes all programs running on the computer. However, the computer still runs. Using the Start menu to shut down Lock: Locks the computer Work on any programs running can be resumed on unlocking the computer. Restart. If due to some error the computer needs to be shut down, then it can be restarted by using the Restart option. This option shuts down Windows completely and then starts it again immediately. Sleep: Puts the computer in a low-power state and saves any work being done that it can be resumed from the point where it was left off FACT FILE Like \"Sleep\" in desktop PCs, \"Hibernate\' is a power-saving mode developed for laptops It keeps the active documents and programs running on the hard disk and puts the computer in a low-power state so that work can be resumed quickly. This allows the users to restore work even in the case of a power failure. ACTIVITY Find out more about mobile operating systems. List the various mobile operating systems available GLOSSARY ARY BIOS A built-in software into a computer\'s RAM Booting The process that starts the operating system when the user turns on a computer system. Cold boot The process of pressing the Power button when the computer is shut down. MBR The information that BIOS copies onto the RAM. Multi-user operating system An operating system that supports multiple users at the same time and/or different times. Operating system System software that is an interface between the user and the computer POST Power-On Self Test conducted by BIOS to make sure all the components of the computer are in a working condition. Single-user operating system An operating system where only one user can effectively work on a computer at a time. Warm boot The process of pressing the Restart button while the computer is already on.