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.
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...
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
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
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
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
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 uses preemptive multitasking.
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.
Windows XP Professional is made for business 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 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...
Database Concepts
A database is a collection of logically related information in an organised way so that it can be easily accessed, managed and updated. Some other operations can also be performed on database such as adding, updating and deleting data. A database could be simple as a single text file with a list of names or it could be complex as a large bunch of text files including some data.
Fundamentals of Database
For defining database, two terms, which are used frequently with database, should be known.
Data These are raw and unorganised facts that need to be processed such as digital representation of text, numbers, graphical images or sound, e.g. a student's test score is one piece of data.
Information When data is processed, organised, structured or presented in a given context to make it useful or meaningful, it is called information, e.g. the class's average score is the information that can be concluded from the given data.
Types of Database
Databases are of three types, namely as follows
Network Database In this type of database, data is represented as collection of records and relationships among data are represented as links.
Hierarchical Database In this type of database, data is organised in the form of tree with nodes. Nodes are connected via links.
Relational Database This database is also known as structured database in which data is stored in the form of tables. Where, columns define the type of data stored in the table and rows define the information about the data.
Components of a Database
A database consists of several different components. Each component listed, is called an object. Within the file, you can divide your data into separate storage containers called tables view, add and update table data by using online forms; find and retrieve the data that you want by using queries and analyse or print data in a specific layout by using reports.
Database components are described below
Tables These are the building blocks or relation of any relational database model where all the actual data is defined and entered. Different types of operation are done on the tables such as storing, filtering, retrieving and editing of data. Tables consist of cells at the intersection of records (rows) and fields (columns), -which are describe below
(i) Field It is an area (within the record). reserved for a specific piece of data. e.g. customer number, customer name, street address, city, state, phone number, current address, etc. Field of a table is also known as column.
(ii) Record It is the collection of data items of all the fields pertaining to one entity, i.e. a person, company, transition, etc. Record of a table is also known as row or a tuple and the number of records in a relation is called the cardinality of that relation.
Queries These are basically questions based on the data available in a database. A query more...
Data Communication and Networking
The term communication means sending or receiving information. When we communicate, we share information or data. A communication system can be defined as the collection of hardware and software that facilitates intersystem exchange of information between different devices.
Data Communication
It is the exchange of data between two devices using some form of transmission media. It includes the transfer of data or information and the method of preservation of data during the transfer process. Data is transferred from one place to another in the form of signals. There are three types of signals
Digital Signal In this signal, data is transmitted in electronic form of data, i.e. binary digits (0 or 1).
Analog Signal In this signal, data is transmitted in the form of radiowaves like in telephone line.
Hybrid Signal These signals have properties of both analog signal and digital signal.
Communication Channel
The communication channel refers to the direction of signal flow between two linked devices.
Types of Communication Channel
There are mainly three types of communication channel
(i) Simplex Channel In this channel, the flow of data is always in one direction, with no capability to support response in other direction. This communication is unidirectional. Only one of the communicating devices transmits information and the other can only receive it. e.g. Radio, Television, Keyboard, etc.
(ii) Half Duplex Channel In this channel, the data can flow in both directions, but not at a same time. When one device transmits information, then other can only receive at that point of time. e.g. Walkie-Talkie.
(iii) Full Duplex Channel In this channel, the How of data is in both directions at a time, i.e. both stations can transmit and receive information simultaneously, e.g. Wireless handset (mobile phone).
Communication Media
Communication media of a network refer to the transmission media or the connecting media used in the network. It can be broadly defined as anything that can carry information from a source to destination. It refers to the physical media through which communication signals can be transmitted from one point to another.
Transmission media can be divided into two broad categories
Guided Media or Wired Technologies
The data signal in guided media is bound by the cabling system that guides the data signal along a specific path. It consists of a cable composed of metals like copper, tin or silver.
Basically, they are divided into three categories
(i) Ethernet Cable or Twisted Pair In this pair, wires are twisted together, which are surrounded by an insulating material and an outer layer called jacket. A twisted pair consists of two conductors (copper). One of the wires is used to carry signals to the receiver and the other is used only as a ground reference. It is used as a short distance communication, e.g. Local area networks use twisted pair cable.
(ii) Co-axial Cable It carries the signal of higher frequency data more...
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
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... 
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
(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
