# Current Affairs Railways

#### Data Representation

Data Representation   Data representation refers those methods which are used internally to represent information stored in a computer. Computers store lots of different types of information as numbers, text, graphics, sounds, etc.   Number System It defines a set of values that is used to represent quantity. Digital computers internally use the binary number system to represent data and perform arithmetic calculations.   Types of Number System The number systems generally used by a computer are as follows   Binary Number System This system is very efficient for computers, but not for humans. It contains only two unique digits 0's and 1's. It is also known as Base 2 system. The binary numbers 0 and 1 are called a bit. The computer always calculates input in binary form. e.g. (10101 )2 Here, 2 represents base of binary number.
 A list of the first several power of 2 is    $2{}^\circ =1,\,{{2}^{1}}=2,\,{{2}^{2}}=4,\,{{2}^{3}}=8,\,{{2}^{4}}=16,\,{{2}^{5}}=32,$ ${{2}^{6}}=64,\text{ }{{2}^{7}}=128,\text{ }{{2}^{8}}=256,\text{ }{{2}^{9}}=512,$ ${{2}^{10}}=1024,\text{ }{{2}^{11}}=2048~$
Decimal Number System It consists of 10 digits from 0 to 9. These digits can be used to represent any numeric value. It is also g known as Base 10 system or positional number system, e.g. ${{(1275)}_{10,}}$${{(10406)}_{10}}~$ Octal Number System It consists of 8 digits from 0 to 7. It is also known as Base 8 system. Each position of the octal number represents a successive power of eight.
 A list of the first several powers of 8 s    $8{}^\circ =1,{{8}^{1}}=8,\,\,{{8}^{2}}=64,{{8}^{3}}=512,{{8}^{4}}=4096,{{8}^{5}}=32768$
Representation of Octal Numbers in Binary
 Octal Binary Digits 0 000 1 001 2 010 3 011 4 100 5 101 6 110 7 111
Hexadecimal Number System It provides us with a shorthand method of working with binary numbers. There are 16 unique digits available in this system. These are 0 to 9 and A to F, where A denotes 10, B denotes 11....... F denotes 15. It is also known as Base 16 system or simply Hex. So, each position of the hexadecimal number represents a successive power of 16.
 A list of the first several powers of 16 is $16{}^\circ =1,{{16}^{1}}=16,{{16}^{2}}=256,$ ${{16}^{3}}=4096,{{16}^{4}}=65536~$
Decimal, Binary, Octal and Hexadecimal Equivalents
0 0000 more...

#### Computer Memory

Computer Memory   The computer memory is one of the most important elements in a computer system. It stores data and instructions required during the processing of data and output results. Storage may be required for a limited period of time, instantly or for an extended period of time. It also relates to many devices that are responsible for storing data on a temporary or a permanent basis.   Memory Hierarchy The hierarchical arrangement of storage in current computer architectures is called the memory hierarchy. The computer uses a hierarchy of memory that is organised in a manner to enable the fastest speed and largest capacity of memory as shown in figure.   Parameters of Memory                Some related parameters of memory are as follow                           (i) Storage Capacity It is representative of the size of memory. The capacity of internal memory and main memory can be expressed in terms of number of words or bytes. (ii) Access Modes A memory is comprised of various memory locations. The information from these memory locations can be accessed randomly, sequentially and directly. (iii) Access Time The access time is the time required between the desired modes for a read or write operation till the data is made available or written at the desired location. (iv) Physical Characteristics In this respect, the devices can be categorised into four main categories as electronic, magnetic, mechanical and optical. (v) Permanence of Storage Its permanence is high for future use in magnetic materials.   Types of Memory In general, the memory is classified into two categories as follows (a) Primary memory or Main memory (b) Secondary memory or Auxiliary memory   Primary Memory The memory unit that communicates directly with the CPU is called main memory or the internal memory. The primary memory allows the computer to store data for immediate manipulation and to keep track of what is currently being processed. It is volatile in nature, it means that when the power is turned OFF, the contents of the primary memory are lost forever. Primary memory can be further classified in two categories which are as follows   Random Access Memory It is also known as read/write memory that allows CPU to read as well as write data and instructions into it. RAM (Random Access Memory) is used for the temporary storage of input data, output data and intermediate results. There are two categories of RAM as follows (a) Dynamic RAM (DRAM) It is made up of memory cells where each cell is composed of one capacitor and one transistor. DRAM must be refreshed continually to store information. DRAM is slower, less expensive and occupies less space on the computer's motherboard. (b) Static RAM (SRAM) It retains the data as long as power is provided to the memory chip. It needs not be refreshed periodically. SRAM uses multiple transistors for each memory cell. It does not use more...

#### Computer Architecture

Computer Architecture   Computer architecture deals with the functional behaviour of a computer system as viewed by a programmer. It can also be described as the logical structure of the system unit that housed electronic components. The computer architecture forms the backbone for building successful computer systems.     Components of Computer A computer consists of following main components
• Input/Output (I/O) Unit
• Central Processing Unit
• Memory Unit
•   Input Unit The computer accepts coded information through input unit by the user. It is a device that is used to give required information to the computer, e.g. keyboard, mouse, etc. An input unit performs the following functions (i) It accepts the instructions and data from the user. (ii) It converts these instructions and data in computer in acceptable format. (iii) It supplies the converted instructions and data to the computer system for further processing.   Output Unit This unit sends the processed results to the user. It is mainly used to display the desired result to the user as per input instruction, e.g. video monitor, printer and plotter, etc. The following functions are performed by an output unit (i) It accepts the results produced by the computer which are in coded form and hence cannot be easily understood by us. (ii) It converts these coded results to human acceptable form. (iii) It supplies the converted results to the user.   Central Processing Unit (CPU) It consists of set of registers, arithmetic logic unit and control unit, which together interpret and execute instructions in assembly language. The primary functions of the CPU are as follow (i) The CPU transfers instructions and input data from main memory to registers, i.e. internal memory. (ii) The CPU executes the instructions in the stored sequence. (iii) When necessary, CPU transfers output data from registers to main memory. Central Processing Unit is often called the brain of computer. The CPU is fabricated as a single Integrated Circuit (1C) and is also known as microprocessor. A CPU controls all the internal and external devices and performs arithmetic and logic operations. The CPU consists of following main sub-systems   Arithmetic Logic Unit ALU contains the electronic circuitry that executes all arithmetic and logical operations on the available data. ALU uses registers to hold the data that is being processed. Most ALUs can perform the following operations (a) Logical operations (AND, NOT, OR, XOR) (b) Arithmetic operations (addition, subtraction, multiplication and division). (c) Bit-shifting operations (shifting or rotating a word by a specified number of bit to the left or right with or without sign extension). (d) Comparison operations (=, <, < =, >, > =)
Registers These are special purpose and high speed temporary memory units. Registers are not referenced by their address, but are directly accessed and manipulated by the CPU during execution. Registers store data, instructions, address and intermediate results of processing. The number and size of more...

#### Computer Hardware

Computer Hardware   Computer hardware refers to the physical components of a computer that can be seen and touched by the user. By the use of these hardware devices, it made very easy for the computer for processing its data, store and retrieve. Hardware is one of the basic and necessary part of a computer system. Computer hardware also includes communication bus, ports, input devices, output devices, etc.   Input Devices An input device can be defined as an electro mechanical device that allows the user to feed data into the computer for analysis and storage and to give commands to the computer. The data is entered into the main memory through the input devices. They accept instructions from the user and convert the accepted instructions into the machine language. Some of the commonly used input devices are described below   Keyboard   It is one of the most common input devices. The user can type text and command using this device. The layout of the keyboard was borrowed from the regular typewriter with some additional keys. Keyboard is used to enter data or information in a computer system, which may be in numeric form or alphabetic form. When key is pressed, keyboard interacts with a keyboard controller and keyboard buffer. Keyboard controller stores the code of pressed key in keyboard buffer. There are different types of keyboard such as QWERTY, DVORAK and AZERTY.   Types of Keys on Keyboard The keys are categorised under the following groups (a) Alphanumeric Keys include the alphabet keys (A, B, C, ..., Z) and number keys (0, 1, 2, 3, .... 9). (b) Numeric Keys are located at the right hand side of the keyboard. They consist of digits and mathematical operators. (c) Function Keys are the programmable keys, i.e. the programs can assign some specific actions. They are numbered from F1 to F12. (d) Cursor Control Keys include four directional (left, right, up, down) arrow keys that are arranged in a inverted T formation between the alphanumeric and numeric keypad. Above the arrow keys there are four more keys to control the cursor. These are as follows
• Home It is used to return the cursor to the beginning of the line or the beginning of a document.
• End It moves the cursor to the end of line.
• Page Up When it is pressed, the page view will be moved up one page and cursor goes to the back page.
• Page Down When it is pressed, the page view will be moved down one page and cursor goes to the next page.
(e) Other Keys A keyboard contains some other keys such as follows
• Control Key It performs a special operation with the combination of other keys.
• Enter Key It is used to finish an entry and begin the new entry in a document.
• Shift Key more...

#### Introduction to Computer

Introduction to Computer   A computer is an electronic machine that accepts data from the user, processes the data by performing calculations and operations on it and generates the desired output as a result. The term computer is derived from the Latin word 'computare' which means 'to compute'.   Generally, computer is the combination of Hardware and Software which converts data into information. Computer operates on set of instructions only, they cannot think as human being. Computer has an ability to store and execute set of instructions called program which makes it extremely distinguishable and versatile than calculators. Computer makes people's lives easier and more comfortable.     Functioning of a Computer Computer Performs four basic functions -which are as follows
• Input Information or data that is entered into a computer is called input. It sends data and instructions to the Central Processing Unit (CPU).
• Processing It is the sequence of actions taken on data to convert it into information which is meaningful to the user. It can be calculations, comparisons or decisions taken by the computer.
• Output It makes processed data available to the user. It is mainly used to display the desired result to the user as per input instructions.
• Storage It stores data and programs permanently. It is used to store information during the time of program execution and possible to get any type of information from it.
•   Features of Computer The key features of computer are as follows
• Speed The computer can process data very fast at the rate of millions of instructions per second.
• Accuracy Computers provide a high degree of accuracy. They respond to the user as per the input instructions.
• Storage Capacity Computers are capable to store huge amount of data which depends on the capacity of hard disk.
• Versatility Computers can do different types of work simultaneously. They can perform multiple tasks at a same time.
• Automatic Once the instruction to do any work is given to the computer, the computer does its work automatically by itself.
• Diligency Unlike human beings, a computer is free from monotony, tiredness, lack of concentration, etc and can work for hours without creating any errors.
• Secrecy Leakage of information is reduced by creating login system with password protection.
• Reliability Computer are more reliable than human beings. Computers always produce exact results. The possibility of errors occur only if the input is wrong, i.e. the computers never make mistakes of their own accord.
• Plug and Play Computers have the ability to automatically configure a new hardware and software component.
•    Terms Related to Computer
• Hardware It is the collection of physical elements that constitute a computer system. It is a comprehensive term for all the physical parts of a computer, e.g. display screens, disks, keyboards, etc.
• Software It is more...

• #### Computer Software

Computer Software   Software is a collection of computer programs and related data that provide the instructions for telling a computer what to do and how to do. A software is a interface between the user and the computer. It is a set of instructions, programs that are used to give command to the hardware. It is responsible for controlling, integrating and managing the hardware components of a computer system and for accomplishing specific tasks.   Types of Software Software can be divided into two major categories
• System software
• Application software
•     System Software It consists of several programs, which are directly responsible for controlling, integrating and managing the individual hardware components of a computer system. System software also provides the interface between the user and components of the computer. The purpose of system software is to insulate the applications programmer as much as possible from the detail of the particular complex computer being used. Depending on the functionality, the system software can be further divided into two major categories; system management program and system utilities.   System Management Program It includes an integrated system of programs, which manages the operations of the processor, controls input/output, manages storage resources and provides various support services. Some common examples of system management programs are operating system and device drivers. (a) Operating System It consists of programs, which control, coordinate and supervise the activities of the various components of a computer system. Its function is to provide link between the computer hardware and the user. Operating system performs all internal management functions (disk access, memory management, task scheduling and user interfacing) and ensures systematic functioning of a computer system. It provides an environment to run the programs, e.g. MS-DOS, Windows XP/2000/98, Unix, Linux, etc. The operating system performs the following functions
• It recognises input from keyboard, sends output to the display screen.
• It makes sure that programs running at the same time do not interfere with each other.
• It is also responsible for security, ensuring that unauthorised users do not access the system.

 BIOS The Basic Input/Output System (BIOS) is commonly known as System BIOS. The BIOS controls various electronic components within the main computer system. The initial function of the BIOS is to initialize system devices such as the RAM, hard disk, CD/DVD drive, video display card and other hardwares,
(b) Device Drivers A software, which is written with the objective of making a device functional when it is connected to the computer is called device driver. It is a system software that acts like an interface between the device and the user. Every device, whether it is a printer, monitor, mouse or keyboard has a driver program associated with it for its proper functioning.   System Utilities These programs perform tasks related to more...

#### Operating System

Operating System   An operating system consists of a set of programs, which controls, coordinates and supervises the activities of the various components of a computer system. It is a program which acts as an interface between the user and the hardware. The interface enables a user to utilise hardware resources very efficiently. Operating system (OS) is an organised collection or intergrated set of specialised programs that controls the overall operations of a computer. It is a program that must be on any computer for proper booting.   Functions of Operating System Operating system is a large and complex software consisting of several components. It is responsible for managing all the resources attached to a computer system. Following functions are provided by an operating system to the convenience of users   Process Management ‘A Process is a program under execution'. It is the task which is currently being executed by the processor (CPU). The operating system handles the creation and deletion of processes and also manages the scheduling and synchronisation of process. Process management is the important part of an operating system which enables the activities of planning, monitoring and performance of a process.   Memory Management Memory management of an operating system takes care of allocation and de-allocation of main memory to various processes. Managing the primary memory, sharing and minimising memory access time are the basic goals of the memory management. It also keeps track of memory usage. The performance of memory management is crucial for the performance of entire system.   File Management File management module of operating system manages files held on various storage devices as well as transfers file from one storage device to another. The file management includes creating and deleting both files and directories, allocating space for files, keeping back-up, securing, easy access to files.   Input/Output Management The Input/Output management module of the OS coordinates and assigns different input and output devices, namely terminals, printers, disk drives, tape drives, etc. Input/Output Management controls all I/O devices, keeps track of I/O requests, issues commands to these devices and takes measures which would ensure that data is transmitted efficiently and correctly to and from I/O devices.   Types of Operating System The operating systems are classified as   Batch Processing Operating System In batch processing operating system, a number of jobs are put together and executed as a group. This operating system is responsible for scheduling the jobs according to priority and the resource required. It is the type of OS which does not interact with the computer directly, e.g. Unix.   Single User Operating System It is a type of operating system which allows only one user at a time. Operating system for personal computer (PC) is single user OS. They are designed to manage one task at a time. e.g. MS-DOS, Windows 9X.     Multi User Operating System This OS allows multiple users to access a computer system concurrently. It is used in computer more...

#### Programming Concepts

Programming Concepts   It is the sequence of instructions in which the problems of computer tasks and steps are performed with the help of computer. A person who writes or performs the program is known as programmer. Programmer uses some specific languages to write program which is known as programming languages e.g. C++, Java, etc.   Programming Language It is a set of keywords, symbols and a system of rules for constructing statements by which humans can communicate instructions to be executed by a computer. Programming languages are mainly categorised into three parts which are as follows   Low Level Language These programming languages are more arcane and difficult to understand. It is designed to operate and handle the entire instruction set of a computer system directly which are generally used to write the system software, e.g. Machine language and Assembly language.   Machine Language It is the only language understood by the computers. Sometimes, it referred to as machine code or object code or binary language. It is a collection of binary digits (0 or 1) or bits that the computer reads and interprets.   Assembly Language It is a low level programming language which is used as an interface with computer hardwares. It uses structured commands as substitutions for numbers, allowing humans to read the code easier than looking at binary codes.   Medium Level Language It serves as the bridge between raw hardware and programming layer of a computer system. It is designed to improve the translated code before it is executed by the processor. C language is known as medium level language.   High Level Language (HLL) It is an advanced computer programming language that is not limited to one computer, designed for a specific job and is easier to understand. The main advantage of high level languages over low level languages is that they are easier to read, write and understand, e.g. BASIC, C, FORTRAN, Java, Pascal, etc.   Some High Level Languages and Their Application Areas
Language Year Developer Application Area Nature
FORTRAN (Formula Translation) more...

#### Microsoft Windows

Microsoft Windows   Microsoft Windows stands for 'Microsoft- Wide Interactive Network Development for Office Work Solution.' Microsoft Windows is a series of graphical interface operating system developed, marked and sold by Microsoft. It enables you to work with a wide variety of programs on your computer, often simultaneously.   Versions of MS-Windows Some important versions of MS-Windows are as follows   Windows NT (New Technology) A version of Windows introduced in July, 1993 and made specifically for businesses offering better control over workstation capabilities to help network administrators.   Features
• It is based on High Level Language.
• It is able to run on DOS, Windows 3 and Win 32 applications.
• It has a 32-bit Windows applications.
• It provides higher stability and security.
Windows 95 It is a graphical user interface based operating system. It was released on 24th August, 1995 by Microsoft.   Features
• It is a mixed of 16-bit/3 2-bit Windows operating system.
• It is consumer-oriented.
• It supports graphical user interface operating system.
• It supports FAT32 file system, multi-display, Web TV and the Internet Explorer.
Windows 98 It was developed in 1998. This was produced in two main versions. The first Windows 98 version was plagued with programming errors but the Windows 98 second edition came out later was much better with many errors resolved.   Features
• It supports Internet Explorer 4.0.1.
• It has Intel 80486DX2/66 MHz or a compatible CPU with a Math coprocessor (Pentium processor recommended).
• Windows 98 was the first operating system to use the Windows Driver Model (WDM).
• It includes a FAT32 converter utility for converting FAT16 drives to FAT32 without formatting the partition.
• It also supports many peripherals devices (MX, USE, DVD).
Windows ME An upgraded version from Windows 98 (Millennium Edition) launched in June 2000, but it has been historically plagued with programming errors which may be frustrating for home users.   Features
• It is designed for single CPU or SMP 32-bit Intel X86 computer.
• It supports 8 or more CPU (the maximum 32 CPU).
• The minimum internal storage is 64MB and maximum 4GB.
• It introduced Multilingual User Interface (MUI).
Windows XP It is an OS produced by Microsoft for use on personal computers. Microsoft released Windows XP on 25th October, 2001. Some versions of Windows XP are as follows
• Windows XP Home edition is a version made for home users.
Features It has various users with independent profiles. It has 3.75 GB free space on the disk and that the total size of the disk is 19.5 GB. At least 64 MB of RAM internal storage. It provides 1.5 GB of available space on the hard disk. It includes video adapter and monitor with Super VGA $\left( 800\times 600 \right)~$or higher resolution. It more...

#### Microsoft Office

Microsoft Office   Microsoft Office was developed by Microsoft Inc in 1988. It is a collection of software’s, based on specific purpose and mainly used in office work. You can start any software of MS-Office by using the Start button.   There are five packages of MS-Office
• MS-Word (Word Processing Software)
• MS-Excel (Tabular Data Formatting Software)
• MS-PowerPoint (Presentation Software)
• MS-Access (Database Management Software)
• MS-Outlook (E-mail Client)
•   Microsoft Word MS-Word is a Word processing application which is one of the most important and widely used applications found on computer. Word processing software is mainly used to the creation of text based documents. It provides tools for composing, editing, formatting and printing of documents smaller than 45 Kb. The document can be a poster, report, letter, brochure. Web page, newsletter, etc. e.g. WordStar, Easy Word, Notepad for Windows.   Start MS-Word There are two methods of starting MS-Word which are as follows (i) Click on Start button and type run on text box than click on Run after that Run dialog box will be appear on screen. Now type winword on text box and press Enter. (ii) Click Start button $\to$ All Programs $\to$ Microsoft Office $\to$ Microsoft Office Word 2007. It opens MS-Word with a blank document. By default, the name of the blank document is Document1.docx, where .docx is the extension of a MS-Word file.   Components of Microsoft Word The components of MS-Word are as follows (i) Title Bar 'It shows the name of the application and name of the file. It consists of three buttons, i.e.     (a) Minimize (reduces the window but Word still active)     (b) Restore (brings Word window to the maximum original size)     (c) Close (brings us out of Word) (ii) Standard Tool Bar It displays the symbol for the common operation like Open, Print, Save, etc. (iii) Ribbon It is a set of tools and commands across the top of the screen. It consists of a panel of commands which     are organised into a set of tabs. (iv) Tab On the ribbon, it contains the buttons needed to edit characters, text and layout. (a) Home tab consists of Clipboard (Cut, Copy, Paste), Font (Size, Color Bold, Italic/Underline), Paragraph (Bullets/ Numbering, Indent), Styles, Editing (Find and Replace). (b) Insert tab consists of Pages (Cover Page, Blank Page, Page Break), Illustrations (Picture, ClipArt, Shapes,      SmartArt, Chart), Links (Hyperiink), Header & Footer. Text (Textbox, Date & Time, Object). (c) Page Layout tab consists of Themes, Page Setup, Page Background, Paragraph. (d) Review tab consists of Spelling & Grammar, Thesaurus, Translate, Compare and Protect Document. (e) View tab consists of Print Layout, Full Screen Reading, Macros, Split, etc.     (v) Ruler It appears on the top of the document window. It allows to format the horizontal or vertical alignment of text in a document. There are two types of rulers (a) Horizontal more...

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