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Basic Concepts of Computer :: 1
BASIC CONCEPTS OF COMPUTER
1.1 INTRODUCTION
A computer is a programmable machine designed to perform arithmetic and logical operations automatically and sequentially on the input given by the user and gives the desired output after processing. Computer components are divided into two major categories namely hardware and software. Hardware is the machine itself and its connected devices such as monitor, keyboard, mouse etc. Software are the set of programs that make use of hardware for performing various functions.
1.2 OBJECTIVES
After going through this lesson you would be able to:
familiarise yourself with characteristics of computers
identify the basic components of a computer
explain the importance of various units of a computer
differentiate between system software and application
software
explain the importance of operating system
get acquainted with open source
appreciate the need of computer security
1.3 CHARACTERISTICS OF COMPUTERS
The characteristics of computers that have made them so powerful and universally useful are speed, accuracy, diligence, versatility and storage capacity. Let us discuss them briefly.
2 :: Computer and Office Applications Speed Computers work at an incredible speed. A powerful computer is capable of performing about 3-4 million simple instructions per second. Accuracy In addition to being fast, computers are also accurate. Errors that may occur can almost always be attributed to human error (inaccurate data, poorly designed system or faulty instructions/programs written by the programmer) Diligence Unlike human beings, computers are highly consistent. They do not suffer from human traits of boredom and tiredness resulting in lack of concentration. Computers, therefore, are better than human beings in performing voluminous and repetitive jobs. Versatility Computers are versatile machines and are capable of performing any task as long as it can be broken down into a series of logical steps. The presence of computers can be seen in almost every sphere – Railway/Air reservation, Banks, Hotels, Weather forecasting and many more. Storage Capacity Today’s computers can store large volumes of data. A piece of information once recorded (or stored) in the computer, can never be forgotten and can be retrieved almost instantaneously.
1.4 COMPUTER ORGANIZATION
Fig.1.1: Computer System
4 :: Computer and Office Applications c. Output Unit: The output unit is used for storing the result as output produced by the computer after processing. d. Processing: The task of performing operations like arithmetic and logical operations is called processing. The Central Processing Unit (CPU) takes data and instructions from the storage unit and makes all sorts of calculations based on the instructions given and the type of data provided. It is then sent back to the storage unit. CPU includes Arithmetic logic unit (ALU) and control unit (CU) Arithmetic Logic Unit: All calculations and comparisons, based on the instructions provided, are carried out within the ALU. It performs arithmetic functions like addition, subtraction, multiplication, division and also logical operations like greater than, less than and equal to etc. Control Unit: Controlling of all operations like input, processing and output are performed by control unit. It takes care of step by step processing of all operations inside the computer.
1.4.2 Memory
Computer’s memory can be classified into two types; primary memory and secondary memory a. Primary Memory can be further classified as RAM and ROM. RAM or Random Access Memory is the unit in a computer system. It is the place in a computer where the operating system, application programs and the data in current use are kept temporarily so that they can be accessed by the computer’s processor. It is said to be ‘volatile’ since its contents are accessible only as long as the computer is on. The contents of RAM are no more available once the computer is turned off.
Basic Concepts of Computer :: 5 ROM or Read Only Memory is a special type of memory which can only be read and contents of which are not lost even when the computer is switched off. It typically contains manufacturer’s instructions. Among other things, ROM also stores an initial program called the ‘bootstrap loader’ whose function is to start the operation of computer system once the power is turned on. b. Secondary Memory RAM is volatile memory having a limited storage capacity. Secondary/auxiliary memory is storage other than the RAM. These include devices that are peripheral and are connected and controlled by the computer to enable permanent storage of programs and data. Secondary storage devices are of two types; magnetic and optical. Magnetic devices include hard disks and optical storage devices are CDs, DVDs, Pen drive, Zip drive etc. Hard Disk Fig. 1.3: Hard Disk Hard disks are made up of rigid material and are usually a stack of metal disks sealed in a box. The hard disk and the hard disk drive exist together as a unit and is a permanent part of the computer where data and programs are saved. These disks have storage capacities ranging from 1GB to 80 GB and more. Hard disks are rewritable.
Basic Concepts of Computer :: 7 Fig. 1.4: Keyboard Mouse: A device that controls the movement of the cursor or pointer on a display screen. A mouse is a small object you can roll along a hard and flat surface (Fig. 1.5). Its name is derived from its shape, which looks a bit like a mouse. As you move the mouse, the pointer on the display screen moves in the same direction. Fig. 1.5: Mouse Trackball: A trackball is an input device used to enter motion data into computers or other electronic devices. It serves the same purpose as a mouse, but is designed with a moveable ball on the top, which can be rolled in any direction. Touchpad: A touch pad is a device for pointing (controlling input positioning) on a computer display screen. It is an alternative to the mouse. Originally incorporated in laptop computers, touch pads are also being made for use with desktop computers. A touch pad works by sensing the user’s finger movement and downward pressure. Touch Screen: It allows the user to operate/make selections by simply touching the display screen. A display Function Keys Numeric Keypad Cursor Movement Keys Alphanumeric Keypad/ Special-function Keys
8 :: Computer and Office Applications screen that is sensitive to the touch of a finger or stylus. Widely used on ATM machines, retail point-of-sale terminals, car navigation systems, medical monitors and industrial control panels. Light Pen: Light pen is an input device that utilizes a light-sensitive detector to select objects on a display screen. (Fig. 1.6) Fig. 1.6 Light Pen Magnetic ink character recognition (MICR): MICR can identify character printed with a special ink that contains particles of magnetic material. This device particularly finds applications in banking industry. Optical mark recognition (OMR): Optical mark recognition, also called mark sense reader is a technology where an OMR device senses the presence or absence of a mark, such as pencil mark. OMR is widely used in tests such as aptitude test. Bar code reader: Bar-code readers are photoelectric scanners that read the bar codes or vertical zebra strips marks, printed on product containers. These devices are generally used in super markets, bookshops etc. Scanner: Scanner is an input device that can read text or illustration printed on paper and translates the information into a form that the computer can use. A scanner works by digitizing an image. (Fig. 1.7)
10 :: Computer and Office Applications Printer: Printers are used to produce paper (commonly known as hardcopy) output. Based on the technology used, they can be classified as Impact or Non-impact printers. Impact printers use the typewriting printing mechanism wherein a hammer strikes the paper through a ribbon in order to produce output. Dot-matrix and Character printers fall under this category. Non-impact printers do not touch the paper while printing. They use chemical, heat or electrical signals to etch the symbols on paper. Inkjet, Deskjet, Laser, Thermal printers fall under this category of printers. Plotter: Plotters are used to print graphical output on paper. It interprets computer commands and makes line drawings on paper using multicoloured automated pens. It is capable of producing graphs, drawings, charts, maps etc. (Fig. 1.9) Fig. 1.9 Plotter Facsimile (FAX): Facsimile machine, a device that can send or receive pictures and text over a telephone line. Fax machines work by digitizing an image. Sound cards and Speaker(s): An expansion board that enables a computer to manipulate and output sounds. Sound cards are necessary for nearly all CD-ROMs and have become commonplace on modern personal computers. Sound cards enable the computer to output sound through speakers connected to the board, to record sound input from a microphone connected to the computer, and manipulate sound stored on a disk.
Basic Concepts of Computer :: 11
1.5 COMPUTER SOFTWARE
Computer software is the set of programs that makes the hardware perform a set of tasks in particular order. Hardware and software are complimentary to each other. Both have to work together to produce meaningful results. Computer software is classified into two broad categories; system software and application software.
1.5.1 System Software:
System software consists of a group of programs that control the operations of a computer equipment including functions like managing memory, managing peripherals, loading, storing, and is an interface between the application programs and the computer. MS DOS (Microsoft’s Disk Operating System), UNIX are examples of system software.
1.5.2 Application software:
Software that can perform a specific task for the user, such as word processing, accounting, budgeting or payroll, fall under the category of application software. Word processors, spreadsheets, database management systems are all examples of general purpose application software. Types of application software are: Word processing software: The main purpose of this software is to produce documents. MS-Word, Word Pad, Notepad and some other text editors are some of the examples of word processing software. Database software: Database is a collection of related data. The purpose of this software is to organize and manage data. The advantage of this software is that you can change the way data is stored and displayed. MS access, dBase, FoxPro, Paradox, and Oracle are some of the examples of database software. Spread sheet software: The spread sheet software is used to maintain budget, financial statements, grade sheets, and sales records. The purpose of this software is organizing numbers. It also allows the users to perform
Basic Concepts of Computer :: 13
1.6.1 Machine Language
Machine language or machine code is the native language directly understood by the computer’s central processing unit or CPU. This type of computer language is not easy to understand, as it only uses a binary system, an element of notations containing only a series of numbers consisting of one and zero, to produce commands.
1.6.2 Assembly Level Language
Assembly Level Language is a set of codes that can run directly on the computer’s processor. This type of language is most appropriate in writing operating systems and maintaining desktop applications. With the assembly level language, it is easier for a programmer to define commands. It is easier to understand and use as compared to machine language.
1.6.3 High Level Language
High Level Languages are user-friendly languages which are similar to English with vocabulary of words and symbols. These are easier to learn and require less time to write. They are problem oriented rather than ‘machine’ based. Program written in a high-level language can be translated into many machine languages and therefore can run on any computer for which there exists an appropriate translator.
1.6.4 Compiler & Interpreter
These are the programs that execute instructions written in a high-level language. There are two ways to run programs written in a high-level language. The most common is to compile the program; the other method is to pass the program through an interpreter. a. Compiler A compiler is a special program that processes statements written in a particular programming language called as source code and converts them into machine language or “machine code” that a computer’s processor uses.
14 :: Computer and Office Applications Compiler translates high level language programs directly into machine language program. This process is called compilation. (Fig 1.11) Fig. 1.11: Compilation b. Interpreter An interpreter translates high-level instructions into an intermediate form, which it then executes. Compiled programs generally run faster than interpreted programs. The advantage of an interpreter, however, is that it does not need to go through the compilation stage during which machine instructions are generated. This process can be time-consuming if the program is long. (Fig 1.12) Fig. 1.12: Interpretation
1.6.5 Open source software:
Open source refers to a program or software in which the source code (the form of the program when a programmer writes a program in a particular programming language) is available to the general public for use and/or modification from its original design free of charge. Open source code is typically created as a collaborative effort in which programmers improve upon the code and share the changes within the community.
16 :: Computer and Office Applications Windows (See Fig. 1.13). Desktop icons provide access to commonly used programs, folders and files. Fig. 1. Overview of the options available in the start menu. Task Description All Programs Displays a list of installed program, which a user can start or use My Documents Displays a list of documents used by the current user My Recent Documents Displays a list of recently used documents by the current user My Picture Displays a list of pictures/photos used by the current user My Music Displays a list of music/songs used by the current user Control Panel Displays a list of utilities to configure the computer system and install software and hardware Printers and Faxes Displays a list of currently installed printers and faxes in the current computer system
Basic Concepts of Computer :: 17 Help and Support Start the XP help and support program to find how to do a task in windows Search Helps the user to find any file or folder from a list of document used by the current user. Run Starts an application program or executes a DOS command Log Off Log off the currently logged in user of the system Turn Off Computer Close currently opened program, log off the current user and switch off the computer system. Task Bar When you start the computer system, then start button and task bar appears on the bottom of the screen and by default remains visible when Windows is running (See Fig. 1.14). Whenever a program is run or a window is opened, an icon representing the program appears on the taskbar. To switch between windows or program, click on the icon representing the window on the task bar. When the program or window is closed, the icon disappears from the task bar. Task bar (^) System Tray Fig. 1. The system tray is part of the task bar and displays the current time as well as the status icons.
1.8.1 Start a Program
To start a program, do the following;
- Click on the Start Button.
- Click on the All Programs, you will see a list of all the program icons and program folders.
- Point to the desired folder say Accessories and select the desired program to run such as Paint.
Basic Concepts of Computer :: 19 Click on the Index tab to locate specific topic listed alphabetically and the follow the instructions displayed on the screen. Click on Favourites tab to add Help Topics, search results to your Favourites list to make them easy to locate in the future Click on History to pick from a list of Help and Support pages that you have read in the past. Click on Support to get various kind of online support such as Microsoft online support, News Group on Windows. Click on Option to configure the help and support center as per your requirement. To close Help and Support windows, select the close button (×) in the upper-right corner of the window.
1.8.4 Searching Files and Folders
If you don’t know where a document or folder is located, you can use the Search option to locate it in the local storage such as Hard Disk, CD or in the network drive (if the system is part of a network). The Indexing Service provided by the Search maintains an index of all the files on your computer, making searches faster. To search for a file or folder
- Click Start , and click on Search.
- Select All files and folders from the left hand side of the windows (see Fig. 1.16).
- Type the name of the file or folder in part or full, or type a word or phrase that exists in the file to be searched.
- If you do not know either piece of information select one or more of the remaining options: In Look in , click the drive, folder, or network you want to search.
20 :: Computer and Office Applications Fig. 1. Click on When was it modified? to look for files that were created or modified on or between specific dates. To look for files of a specific size, click on What size is it? Select a size. Click on More advanced options to specify additional search criteria.
- Once you finish specifying the search criteria, click on Search to locate the file. Similarly you can search for specific information on Internet, or people in your address book, search for a printer or a computer on your network.
1.8.5 Changing System settings
By using Control Panel’s tools you can customize the way Windows look and work! Also you can install new hardware, add and remove (install/uninstall) software programs, change the look and feel of your desktop and much more. It also includes a number of administrative tools in Administrative
