Internet

Internet is a collection of local, regional and national computer networks that are linked together to exchange data and distribute processing tasks. The Internet evolved over the past thirty years from a fledging experiment with four computers into a vast information network that connects millions of microcomputers, minicomputers and mainframe computers. As of 1998, the Internet had more than 100 million users world wide, and that number is growing rapidly. The Internet is decentralized by design and, remarkably, this anarchy by design works well.

An ISP (Internet Service Provider) is a company that charges an ongoing fee for providing Internet access to businesses, organisations and individuals. The ISP provides the user with the necessary communications software (such as e-mail) and user account. The user supplies a modem that connects the computer to the user’s phone line. The user’s computer dials the ISP’s computer and establishes a connection over the phone line. Once connected the ISP routes data between the user’s computer and the Internet. Most ISPs offer dial-up Internet connections and electronic mail access, along with additional services. Some ISPs offer direct access to the Internet without the use of proprietary software.

World Wide Web is a computer network system that allows users to browse through information available
on computers round the world. The World Wide Web opened the Internet to millions of people interested in finding information. There are over one million Web sites around the world and the number is growing very quickly. The World Wide Web consists of documents called Web pages that contain information on a particular topic. A Web page might also contain one or more links that point to other Web pages. Links make it easy to follow a thread of related information, even if the pages are stored on computers located in different countries. Every Web page is stored as an HTML (HyperText Markup Language) document. An HTML document contains special instructions called HTML tags that tell a Web browser how to display the text, graphics, and background of a Web page. Uniform Resource Locator (URL) is the global address of documents and other resources on the World Wide Web. URLs can point to executable files that can be fetched using FTP (file transfer protocol, ftp://) or a Web page that can be retrieved using HTTP (hypertext transfer protocol, http://). To request a Web page the user either types in the URL address or uses a ‘mouse’ to click on a Web page link. After the http://, the next segment of the address is the server name. The server is the computer and software that make the data available. Most Web servers have domain names prefixed with WWW. By entering the Web server name, one accesses the site’s home page (The main page of a Website. Typically, the home page serves as an index or table of contents to other documents stored at the site). A home page is similar to the title page and table of contents in a book. It identifies the site and contains links to other pages at the site.
The Web browser is the gateway to commercial information services as well as the free sites on the Internet. A commercial information service provides access to computer-based information for a fee. In 1997, approximately 17 million people subscribed to the top four commercial information services: America On-Line, CompuServe, Microsoft Network and Prodigy.
The server sends the data for the Web page over the Internet to the computer. The data includes two things: the information the user wants to view and a set of instructions that tells the browser how to display it. The instructions include specifications for the colour of the background, the size of the text, and the placement of the graphics. Additional instructions tell the browser what to do when the user clicks on a link. The browser’s menu and tool bars help users navigate the Web as they follow the links. The Back and Forward buttons trace and retrace the users’ path through the links being followed from one Web page to another. The browser stores and can display a list of the pages being visited during each session. The browser can also store a list of favourite sites, often called bookmarks, to permit the user to jump directly to the site they wish to see instead of having to enter its URL every time.

Networking Computing

A network computing environment is one in which an organization has linked together personal computers that have been connected into a network. There are a number of types of computer networks.
Local area network: A computer network located within a relatively limited area such as a building, agency or university campus. Also known as a LAN.
Wide area network (WAN): A computer network that covers a large geographical area.
The purpose of networking personal computers and even mainframes together is to permit employees in the organization to
• communicate with one another as well as others outside the organization, normally through the use of electronic messages
• access information and services supported on the World Wide Web
• share documents and data
• support various work processes in the organization based on the automation of specific tasks.
A computer that is not connected to a network is referred to as a stand-alone computer. When a computer is physically connected to a local area network, using a cable or other communications channel, the computer becomes a workstation on the network. Each device on the network including workstations, servers, and printers is referred to as a node.
A workstation normally has all of the usual resources found in the personal computing environment (hard drive, software, data and printer). However, users of workstations will also have access to network resources, which typically include application software, storage space for data files, and printers other than those on the local workstation. On a network, the network server typically provides the applications
software and storage space for data files.
An application server is a computer that runs applications software and runs the results of processing to workstations as requested. An application server makes it possible to use the processing power of both the server and the workstation. Use of an application server splits processing between the workstation client and the network server. The method is also referred to as client/server architecture.
The main advantage of a computer network is that all the users can share resources, rather than have users each maintain his or her own resources. It is not necessary to purchase multiple copies of software; instead a license can be purchased to use the software within the network which allows everyone to use the program at the same time.
An internal network that belongs to an organization and is accessible only by that organization members is often referred to as an Intranet. Intranet is an internal computer network that belongs to an organization and is accessible only by that organization's members.

Mainframe computing

Mainframe computing was developed at a time when computational power was an expensive and scarce resource. In order to use the expensive computer technologies efficiently, organizations had to share their resources. Many of computerized such as invoicing, purchasing, payroll, accounting and so on, involved the organization as a whole.
If the original reasons for the mainframe computing model were cost and scarcity of resources, the current reasons for sharing computer power are

• for security: the protection of data from outside or unauthorized access
• for integrity: the guarantee that the data is not corrupted and that repeatability is achievable using the same applications and data
• for system availability: centralized facilities can be operated by teams in shifts 24 hours a day, maximizing the investment in IT equipment and allowing large data processing activities to be carried out efficiently
• for data sharing: data input or created in one part of the organization becomes available to other parts
• for applications: many modern applications, such as personnel management systems, require access to a shared pool of resources.

Nowadays, mainframe computing is no longer an expensive resource, sharing is still a cost-effective means of providing computational power. Recent studies have shown that on a per-user basis, mainframe computing provides the least expensive form of computing.
A large central processor is kept in a purpose-built computer centre staffed by personnel responsible for maintaining it. Individuals in the organisation access the mainframe computer through terminals on their desktops in order to share common organisational resources, such as software programs or electronic data. Nowadays, a mainframe is actually identified more by the ‘environment’ in which the mainframe is operated. In other words, the physical environment: the controlled temperature and humidity and the physical security of having the mainframe behind locked doors.

The mainframe is the data and application repository for most organizations. It is also the hub for most online business activities. It is believed that mainframes still house 90 per cent of the data major organizations rely on to conduct their business. Despite claims that mainframe technology is dying out, sales of mainframe hardware and software remain steady. The term ‘mainframe’ has always had the image of being something large in size. Yet, however big the early ‘room-filling’ mainframes were, today’s modern versions are no bigger than the size of a household refrigerator. The level of mainframe sophistication has grown over the more than thirty years of its evolution; organizations still recognize its advantages in terms of performance, reliability and security.

Virus

It is a computer program that is planted in one computer and then transferred, hidden in useful information, to one or more other computers with the intention of corrupting or wiping out information in the recipient computer. Many different types of viruses exist, ranging from ones that prevent us from opening up word-processed documents through to ones that destroy the entire contents of a hard drive. Viruses can be caught in several ways, for example by exchanging floppy disks, by electronic mail messages and through downloading documents from the Web. Networks make it much easier for viruses to move around. Once a virus gets into computer system it can spread very quickly. New viruses appear each week, so it is essential that users have up-to date anti-virus software to combat this problem.

Documentation

Documentation explains how the various systems or programs operate and accompany computer hardware, software and peripherals. It is the information needed to develop, use or maintain computer hardware and software and to permit access and retrieval of the data. Although documentation usually comes in the form of printed manuals, guide books, it may also come in electronic form, such as in ‘help screens’ contained within the computer software or documentation in data dictionaries and so on. Mostly, it is created when a specific computer application is used. This documentation can be critical to understanding the database system, particularly if it is being managed in an archival environment long after the creators of the system have left.

How are data stored?

A storage device is anything which is used to store computer data. Floppy disks, hard disks, optical disks,
CDs and magnetic tapes are types of storage device.
Physical storage refers to how data are actually kept on the storage disk. The most commonly used medium for storage is magnetic storage. With magnetic storage the computer stores data on disks and tape by magnetising selected particles of an oxide-based surface coating. The two most popular types of magnetic storage media are hard disks and diskettes.

Hard drive or hard disk storage provides faster access to files than a diskette. It is the storage area within the computer itself, where megabytes of space are available to store bits of information. A hard disk platter is a flat, rigid disk made of aluminium or glass and coated with a magnetic oxide. A hard disk consists of one or more platters and their read-write heads. A read-write head is the device that reads the data from the disk platter into the computer. It also writes data onto the platters. Hard disk platters in microcomputers are typically 3½ inches (about 10 centimetres) in diameter: the same size as the circular mylar disk in a diskette. However, the storage capacity of a hard disk far exceeds that of a floppy disk. The access time of a hard disk is also significantly faster than a diskette. Like diskettes, hard disks provide random access to files by positioning the read-write head over the sector that contains the requested data.

Diskette is a small, removable, flexible mylar plastic disk covered with a thin layer of a magnetizable substance, onto which digital data can be recorded and stored. Diskettes are also called floppies. Although today’s microcomputers typically use 3½ inch (about 10 centimetre) disks, we may still find 5¼ inch (about 15 centimetre) disks that were popular many years ago. Finding a disk drive to read 5¼ inch disks may be very difficult. Diskettes are generally used for transporting or shipping data files or for making duplicate copies of data files for back-up purposes. The storage capacity of a diskette varies but is considerably smaller than that of a hard drive.
Other types of storage devices are:
Magnetic tape: It is a continuous plastic strip covered with magnetic oxide, the tape is divided into parallel tracks onto which data may be recorded by selectively magnetising parts of the surface, or spots, in each of the tracks. The data can then be stored and reused.
Back up: It is used to copy a computer files to another medium, usually on a diskette or magnetic tape, so that the data are safe in case the original file is damaged or lost. Backups are usually copied to storage devices that can be removed from the computer and kept separately from the original.
Optical disk: A storage device that uses reflecting surfaces and laser technology to read and write data on a disk is optical disk which is also known as a laser disk. Some types of optical disks are CD-ROM, CD-RW.

How a computer processes information.

When data is input into a computer, the numbers or words we understand are translated into a binary numbers system. Binary is the language of computers. Everything we type, input, output, send, retrieve, draw and so on is converted to the computer’s native language: binary ( it uses only two symbols 0 and 1 to represent values).

In the binary system, each digit position represents a value of 2. Because computers use the binary system, powers of 2 play an important role. This is why everything in computers seems to come in 8s (2 to the 3rd power), 64s (2 to the 6th power), 128s (2 to the 7th power), and 256s (2 to the 8th power).

The work of manipulating, storing and processing the data takes place in the Central Processing Unit, the computer’s main memory. The CPU consists of an arithmetic and logic unit, or ALU, a control unit, and a set of registers.

1. The arithmetic and logic unit is the portion of the CPU where arithmetic and logical operations take place.
2. The control unit is the part of the CPU that supervises the general operations of the computer.
3. The registers are devices that hold data inside the computer’s memory long enough to execute a particular function, such as indexing, calculating, sorting or otherwise manipulating data. They are the CPU’s own internal memory.

The medium through which the data are transferred from one part of computer to another is called bus. The data are input into the computer and processed in the CPU. They travel along the bus to be stored in the computer’s memory. The amount of memory available is described in bytes of information, referring to the combination of bits representing characters. The higher the number of bytes the more memory the computer has. Today’s computers hold ‘megabytes’ or even ‘gigabytes’ of data. A megabyte is a unit of one million bytes; a gigabyte is one billion bytes, and a terabyte is one trillion bytes. If a computer has a memory of 64 megabytes, then it can hold 64 million bytes of information.

Software and it's function

Software is the computerized instructions that operate the computer, execute particular functions or tasks, and manipulate the data. For software to perform various functions, it must be programmed. The instructions need to be written in a programming language that the computer can understand. Without a program, a computer is useless. Over the years, a wide range of programming languages have been developed, including BASIC, FORTRAN, PASCAL, C++, JAVA, and so on. Each language has a unique set of words or codes that it understands and a special syntax for organizing program instructions. The language the computer actually understands is called machine language, which comprises numbers only. This language is used by the computer to understand the programming language and translate the terms into executable instructions. Lying between programming languages and machine languages are assembly languages. Assembly languages have the same structure and set of commands as machine languages but they enable a program to use names instead of numbers.

There are different types of software.

Systems software: It includes the operating system and all the programmes that enable the computer to function. The most important program that runs on a computer is the operating system. Every general-purpose computer must have an operating system in order to run other programs. This includes controlling functions such as the coordination of the hardware and applications software, allocating storage facilities, controlling the input and output devices and managing time sharing for linked or networked computers. In many respects an operating system works like an air traffic controller to coordinate activities within the computer. Examples of operating systems are Windows NT, DOS and OS/2.

Applications software: It includes programs that users access to carry out work. They include applications for the different functions. For example: Word Processing as a common application software to make it easy to manipulate and format documents, Database management applications to let people create and manipulate data in database, communication applications to enable people to send fax and emails to other computers.

How does a computer work?

A computer works in following ways:

1. A computer takes a input through different input devices like keyboard, mouse or other input devices like CD-ROM. These input data may be number or pictures or any words or symbols in order to be processed.

2. Then the computer manipulates the data in many ways and this is called processing. This may be done by calculating, sorting numbers or modifying pictures or documents. It is done in the CPU.

3. The computer stores data. A computer must store data so that it is available for processing. Most computers have more than one location for storing data. The place where the computer stores the data depends on how the data is being used. The computer puts the data in one place while it is waiting to be processed and another place when it is not needed for immediate processing.

4. The computer produces output which is information that has been produced by a computer. Some examples of computer output include reports, documents, music, graphs, and pictures. Output can be in several different formats, such as paper, diskette, or on screen.

Memory

The most common type of memory that most users are familiar with is ‘main memory’ or ‘RAM’ (random-access memory). It is an area in the computer system unit that temporarily holds a user’s data, operating system instructions and program instructions. The word ‘main’ is used to distinguish it from external mass storage devices such as the hard drive or disk drives. Note that the term ‘mass storage’ refers to various techniques and devices for storing large amounts of data; mass storage is distinct from memory because it retains data even when the computer is turned off. Thus mass storage is sometimes referred to as ‘auxiliary storage’. Following are definitions of common storage devices:

Storage: The area within a computer system where data can be left on a longer term basis while it is not

needed for processing.

Diskette: A small, removable, flexible plastic disk covered with a thin layer of a magnetizable substance, onto which digital data can be recorded and stored. Also known as a floppy disk.

Hard drive: The storage area within the computer itself, where megabytes of space are available to store bits of information. It is also known as a hard disk.

Optical disk: It is a storage device that uses reflecting surfaces and laser technology to read and write data on a disk. It is also called as a laser disk.

Magnetic tape: A continuous plastic strip covered with magnetic oxide; the tape is divided into parallel tracks onto which data may be recorded by selectively magnetizing parts of the surface, or spots, in each of the tracks. The data can then be stored and reused.

Other types of memory include
ROM (read only memory): Unlike RAM, ROM is non-volatile and permits the user to read data. Computers always contain a small amount of read-only memory that holds instructions for starting up the computer.
PROM (programmable read-only memory): It is a memory chip on which we can store a program. Once the PROM has been used, we cannot wipe it and use it to store something else. Like ROMs, PROMs are non-volatile.
EPROM (erasable programmable read-only memory): This is a special type of PROM that can be erased by exposing it to ultraviolet light.
EEPROM (electrically erasable programmable read-only memory): It is a special type of PROM that can be erased by exposing it to an electrical charge.

CPU

The central processing unit (CPU) is the heart of the computer. It carries out all of the instructions given in a program, such as a word processing or spreadsheet program. The CPU consists of one or more chips (another name for “integrated circuits”). A microprocessor is a particular type of chip. The original IBM personal computer used the Intel 8088 microprocessor. Most of today’s microcomputers are designed around a microprocessor from one of two product families: x86 or Power. The 80286, 80386, and 80486 models that followed were referred to by the last three digits, 286, 386, and 486. For the next generation, however, Intel broke with tradition and introduced the Pentium in 1993. In 1997, it introduced the Pentium II to address multi-media applications, and most recently the Pentium III to address the new opportunities provided by access to large volumes of information on the world wide Web. Other manufacturers of chips produce chips of similar power and capabilities.

CPU’s are not all equal. Some process data faster than others. A computer contains a system clock that emits pulses to establish the timing of all systems operations. The system clock operates at a speed quite different from a clock that keeps track of the time of the day. The system clock determines the speed at which the computer can execute an instruction, and therefore limits the number of instructions the computer can complete within a specific amount of time. The time to complete an instruction execution cycle is measured in megahertz (MHz) or millions of cycles per second. Although some instructions require multiple cycles to complete, the processor speed should be thought of in terms of the number of instructions the processor can execute in one second. Today, microprocessor speeds exceed 300 MHz. If all other specifications are identical, then higher megahertz ratings means faster processing.

Hardware components

All computers need the hardwares listed below:

Central Processing Unit (CPU): It is the heart of the computer. It is the chip that enable computer to process data. It is also called as processor.

Memory: It is the area of the computer which holds and stores the data which is to processed.

Storage Device: This is the device where the computer stores its data.

Input Device: These are the devices from where data and instructions are entered into a computer to be processed. These are the resources required for the functioning of a process in a computer which is processed to transform into one or many output. For example: mouse, keyboard, scanner etc.

Output Device: It is the device which gives the output of the processed data and instructions. For example: monitor, projector etc.

Components of computer

All computers are made up of two parts. They are Hardware and Software.

Hardware: Basically we can say hardware is the physical components of a technology either it is of computer systems or any other kind. It also means the metal parts and fittings that were used to make different things and more functional historically. Nowadays, it stands for every physical equipment which is used to make the task more efficient. It is the physical equipment that creates, use, manipulate and store electronic data.

Software: Software is the collection of programs and data which provides the instructions to the computer. In comparison to hardware, software is tangible and can't be touched. It is the collection of programs, procedures and applications. It is also the computerised instructions that operate a computer, manipulate the data and execute particular tasks.

Different types of computer

There are different types of computer. Some kinds are detailed below:
Mainframe computers: They are large-sized, powerful multi-user computers that can support large programs. They can perform different actions or processes at the same time. Mainframe computers can be used by as many users at the same time. Large organisations may use these types of computer to execute large-scale processes.

Mini computers: They are mid-sized multi-processing computers. They also can perform several actions at the same time and can support from 4 to 200 users simultaneously. Organisations may use a mini-computer for such tasks as managing the information in a small financial system or maintaining a small database of information about registrations or applications.

Workstations: They are powerful, single-user computers. They have capacity to store and process large quantities of data, but they are only used by one person at a time. However, workstations are typically linked together to form a computer network called a local area network, which means that several people, such as staff in an office, can communicate with each other and share electronic files and data.

Personal computers:They can be called as microcomputers. These are the most popular type of computer in this generation. The PC is a small-sized, relatively inexpensive computer designed for an individual user. Computers may be called ‘desktop’ computers, which stay on the desk, or ‘laptop’ computers, which are lightweight and portable. Organisations and individuals use PCs for a wide range of tasks, including word processing, accounting, desktop publishing, preparation and delivery of presentations, organisation of
spreadsheets and database management.

Introduction to computer

A computer is a programmable machine. It allows the user to store all sorts of information and data and then process that information, carry out actions with the information, such as calculating numbers or organizing words. It is a machine that can receive, store the information and process it as needed.

History of computer

History of modern computer begins with automated calculation and programmability. The computer was first invented by Charles Babbage in 1822 who is also known as the father of computer. Charles Babbage was the one who invented the concept of a programmable computer in about 1856. Dr. John V. Atanasoff and his assistant Clifford Berry build the first electronic digital computer (Atanasoff Berry Computer) in 1939. But the device was designed to solve the system of linear equation. Later in 1941, Konrad Zuse built the first working computer and in 1955, he built the first computer on the basis of magnetic storage. George Stibitz is internationally recognized as a father of the modern digital computer. While working at Bell Labs in November 1937, Stibitz invented and built a relay-based calculator he dubbed the "Model K" (for "kitchen table"), on which he had assembled it), which was the first to use binary circuits to perform an arithmetic operation. Later models added greater sophistication including complex arithmetic and programmability.