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 consists 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...
Internet and Its Services
The Internet has gained popularity and emerged as an important and efficient means of communication. The idea of introducing the Internet was to allow millions of people to share information and ideas, sound, video clips using their computers across the world. The Internet is a worldwide network of networked computers those are able to exchange information with each other. It consists of thousands of separately administered network of various sizes and types.
Internet
Internet stands for International Network, which began in 1950's by Vint Cerf known as the 'Father of Internet. Internet is a 'network of networks' that consists millions of private and public networks of local to global scope. Basically, network is a group of two or more computer systems linked together.
The data move around the Internet is controlled by protocols. Under TCP/IP protocol (Transmission Control Protocol/Internet Protocol), a file is broken into smaller parts by the file server called packets. All computers on the Internet, communicate with one another using TCP/IP, which is a basic protocol of the Internet.
History of Internet
In 1969, the University of California at Los Angeles, the University of Utah were connected as the beginning of the ARPANET (Advanced Research Projects Agency Network) using 50 kbits circuits. It was the world's first operational packet switching network. The goal of this project was to connect computers at different universities and U.S. defence.
In mid 80's another federal agency, the National Science Foundation, created a new high capacity network called NSFnet, which was more capable than ARPANET. The only drawback of NSFnet was that it allowed only the academic research on its network and not any kind of private business on it. So, private organisations and people started working to build their own networks, which were later interconnected with ARPANET and NSFnet to form the Internet.
Advantages of the Internet
(i) Allows you to easily communicate with other people.
(ii) Global reach enables one to connect anyone on the Internet.
(iii) Publishing documents on the Internet saves paper.
(iv) A valuable resource for companies to advertise and conduct business.
(v) Greater access to information reduces research times.
Disadvantages of the Internet
(i) It is a major source of computer viruses.
(ii)Messages sent across the Internet can be easily intercepted and are open to abuse by others.
(iii) Much of the information is not checked and may be incorrect or irrelevant.
(iv) Unsuitable and undesirable material available that sometimes are used by notorious people such as terrorists.
(v) Cyber frauds may take place involving Credit/Debit card numbers and details.
Internet Connections
Bandwidth and cost are the two factors that help you in deciding which Internet connection is to use. The speed of Internet access depends on the bandwidth.
Some of the Internet connections available for Internet access are as follows
Dial-Up Connection
A Dial-up is a method of connecting to the Internet using more...
Computer Security
Computer security is also known as cyber security or IT security. Computer security is a branch of information technology known as information security, which is intended to protect computers. It is the protection of computing systems and the data that they store or access.
Methods to Provide Protection
There are four primary methods to provide protection
System Access Control It ensures that unauthorised users do not get into the system by encouraging authorised users to be security conscious.
Data Access Control It monitors who can access what data, and for what purpose. Your system might support mandatory access controls with these. The sytem determines access rules based on the security levels of the people, the files, and the other objects in your system.
System and Security Administration It performs offline procedures that makes or breaks secure system.
System Design It takes advantage of basic hardware and software security characteristics.
Components of Computer Security
Computer security is associated with many core areas. Basic components of computer security system are
Confidentiality It ensures that data is not accessed by any unauthorised person.
Integrity It ensures that information is not altered by any unauthorised person in such a way that it is not detectable by authorised users.
Authentication It ensures that users are the persons they claim to be.
Access Control It ensures that users access only those resources that they are allowed to access.
Non-Repudiation It ensures that originators of messages cannot deny they are not sender of the message.
Availability It ensures that systems work promptly and service is not denied to authorised users.
Privacy It ensures that individual has the right to use the information and allows another to use that information.
Stenography It is an art of hiding the existance of a message. It aids confidentiality and integrity of the data.
Cryptography It is the science of writing information in a 'hidden' or 'secret' form and is an ancient art. It protects the data in transmit and also the data stored on the disk.
Some terms commonly used in cryptography are
(i) Plain Text It is the original message that is an input.
(ii) Cipher It is a bit-by-bit or character-by character transformation without regard to the meaning of the message.
(iii) Cipher Text It is the coded message or the encrypted data.
(iv) Encryption It is the process of converting plain text to cipher text, using an encryption algorithm.
(v) Decryption It is the reverse of encryption, i.e. converting cipher text to plain text.
Sources of Cyber Attack
The most potent and vulnerable threat of computer users is virus attacks. A computer virus is a small software program that spreads from one computer to another and that interferes with computer operation. It is imperative for every computer user to be aware about the software and programs that can help to protect the personal computers from attacks.
The sources of attack can more...
Those quantities which can describe the laws of physics and possible to measure are called physical quantities. The physical quantities which do not depend upon other physical quantities are called fundamental quantities. In Standard International (S.I.) system the fundamental quantities are mass, length, time, temperature, luminous intensity, electric current and amount of substance. The physical quantities which depend on fundamental quantities are called derived quantities e.g. speed, acceleration, force, etc.
Units
The unit of a physical quantity is the reference standard used to measure it.
Types of Units
Fundamental Units
The units defined for the fundamental quantities are called fundamental or base units.
Fundamental Physical quantity
Mass (M)
Length (L)
Time (T)
Temperature
(\[\theta \]or k)
Electric current (I)
Luminous intensity
Amount of Substance
Fundamental unit
Kilogram (kg)
Meter (m)
Second (s)
Kelvin (k)
Ampere (A)
Candela (cd)
Mole (mol)
Derived Units
The units defined for the derived quantities are called derived units, e.g. unit of speed or velocity (metre per second),
Acceleration (metre per second\[\sec on{{d}^{2}}\]) etc.
Dimensions
The limit of a derived quantity in terms of necessary basic units is called dimensional formula and the raised powers on the basic units are dimensions.
Elasticity and Plasticity
The property of the body to regain its original configuration (length, or shape) when the deforming forces are removed is called elasticity. On the other hand, if the body does not have any tendency to regain its original configuration on removal of deforming force the body is called plastic body and this property is called plasticity.
Perfectly elastic body: A body which regains its original configuration immediately and completely after the removal of deforming force from it, is called perfectly elastic body. Quartz and phosphor bronze, are closed to perfectly plastic body.
Perfectly plastic body: A body which does not regain its original configuration at all on the removal of deforming force, however small the deforming force may be is called perfectly plastic body. Putty mid mud are closed to perfectly plastic body.
Stress
The internal restoring force acting per unit area of a body is called stress. i.e., Stress = Restoring force/Area
Strain
The ratio of change in configuration to the original configuration is called strain.
\[strain=\frac{Change\,in\,\,configuration}{Original\,Configuration}\]
Strain being the ratio of two like quantities has no units and dimensions.
Elastic Limit
Elastic limit is the upper limit of deforming force up to which, if deforming force is removed, the body regains its original form completely and beyond which, if deforming force is increased, the body loses its property of elasticity and gets permanently deformed.
Hooke's low
It states that within the elastic limit stress is directly proportional to strain.
i.e.. Stress \[\propto \]strain or Stress =\[E\times \] strain
Stress or \[\frac{Stress}{strain}=E=Cons\tan t\]
Here E is the coefficient of proportionality and is called modulus of elasticity or coefficient of elasticity of a body:
Materials-Ductile, Brittle and Elastomers
(i) Ductile materials: The materials which have large range of plastic extension are called ductile materials. They can be drawn into thin wires, e.g., copper, silver, aluminium, iron, etc.
(ii) Brittle materials: The materials which have very small range of plastic extension are called brittle materials. These materials break as soon as the stress is increased beyond the elastic limit, e.g., glass, ceramics, cast iron, etc.
(iii) Elastomers: The materials which can be stretched to large values of strain are called elastomers. e.g., rubber, elastic tissue of aorta, etc.
Young's modulus of elasticity (Y): It is defined as the ratio of normal stress to the longitudinal strain within the elastic limit. Thus, \[Y=\frac{Normal\,Stress}{Longitudinal\,Strain}\] or, \[Y=\frac{F/\pi {{r}^{2}}}{\Delta l/{{L}_{0}}}=\frac{Mg{{L}_{0}}}{\pi {{r}^{2}}\Delta l}\]
Thermal Stress
When a rod is rigidly fixed at its two ends and its temperature is changed, then a thermal stress is set up in the rod. And the corresponding strain developed is called thermal strain, Thermal stress \[=\frac{Force}{Area\,\,of\,\,cross\,\,\sec tion}=\frac{F}{A}=Y\alpha \Delta \theta \] Area of cross section A where \[\alpha \] = coefficient of linear expansion of the rod \[\Delta \theta \] = change in temperature. more...
(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... 
