E-MAIL

E-MAIL

E-mail (electronic mail) is the exchange of computer-stored messages by telecommunication. E-mail messages are usually encoded in ASCII text. However, you can also send non-text files, such as graphic images and sound files, as attachments sent in binary streams. E-mail was one of the first uses of the Internet and is still the most popular use. A large percentage of the total traffic over the Internet is e-mail. E-mail can also be exchanged between online service provider users and in networks other than the Internet, both public and private.
E-mail can be distributed to lists of people as well as to individuals. A shared distribution list can be managed by using an e-mail reflector. Some mailing lists allow you to subscribe by sending a request to the mailing list administrator. A mailing list that is administered automatically is called a list server.
E-mail is one of the protocols included with the Transport Control Protocol/Internet Protocol (TCP/IP) suite of protocols. A popular protocol for sending e-mail is Simple Mail Transfer Protocol and a popular protocol for receiving it is POP3. Both Netscape and Microsoft include an e-mail utility with their Web browsers.

Advantages of Email

The benefits of e-mail are huge in number.

• Easy to use: E-mail frees us from the tedious task of managing data of daily use. It helps us to manage our contacts, send mails quickly, maintain our mail history, store the required information, etc.
• Speed: The e-mail is delivered instantly, anywhere across the globe. No other service matches the e-mail in terms of speed.
• Easy to prioritize: Since the mails have subject lines, it is easy to prioritize them and ignore unwanted mails.
• Reliable and secure: Constant efforts are being taken to improve the security in electronic mails. Thus making it one of the secured ways of communication.
• Informal and conversational: The language used in e-mails is generally simple and thus makes the communication informal. Sending and receiving e-mails takes less time, so it can be used as a tool for interaction.
• Easier for reference: When one needs to reply to a mail, there is a provision in the mailing system to attach the previous mails as references. This refreshes the recipient's knowledge, on what he is reading.
• Automated e-mails: It is possible to send automated e-mails using special programs like the autoresponders. The autoresponders reply back to the sender with generalized pre-written text messages.
• Environment friendly: Postal mails use paper as a medium to send letters. Electronic mail thus, saves a lot of trees from being axed. It also saves fuel needed in transportation.
• Use of graphics: Colorful greeting cards and interesting pictures can be sent through e-mails. This adds value to the e-mail service.
• Advertising tool: Many individuals and companies are using e-mails to advertise their products, services, etc.

Disadvantages of Email

The e-mails, though beneficial in our day-to-day life, has got its own drawbacks that are off late coming to the fore.

• Viruses: These are computer programs having the potential to harm a computer system. These programs copy themselves and further infect the computer. The recipient needs to scan the mails, as viruses are transmitted through them and have the potential to harm computer systems.
• Spam: E-mails when used to send unsolicited messages and unwanted advertisements create nuisance and is termed as Spam. Checking and deleting these unwanted mails can unnecessarily consume a lot of time, and it has become necessary to block or filter the unwanted e-mails by means of spam filters. Spamming includes, sending hoax e-mails. E-mail spoofing is another common practice, used for spamming. Spoofing involves deceiving the recipient by altering the e-mail headers or the addresses from which the mail is sent.
• Hacking: The act of breaking into computer security is termed as hacking. After the e-mail is sent and before it is received by the desired recipient, it "bounces" between servers located in different parts of the world. Hence, the e-mail can be hacked by a professional hacker.
• Misinterpretation: One has to be careful while posting any kind of content through an e-mail. If typed in a hurry, the matter could be misinterpreted.
• Lengthy mails: If the mail is too long and not properly presented the reader may lose interest in reading it.
• Not suitable for business: Since the content posted via e-mails is considered informal, there is a chance of business documents going unnoticed. Thus, urgent transactions and especially those requiring signatures are not managed through e-mails.
• Crowded inbox: Over a period of time, the e-mail inbox may get crowded with mails. It becomes difficult for the user to manage such a huge chunk of mails.

Need to check the inbox regularly: In order to be updated, one has to check his e-mail account regularly.

TYPES OF COMPUTER

TYPES OF COMPUTER

Desktop Computer

Laptop Computer

Palmtop Computer

Desktop

A desktop computer is an independent personal computer that is too large to carry easily or set up quickly. It is designed to remain in the same place. Desktops are currently the cheapest and most common computers, and are frequently used by businesses, schools, households and other organizations. Nearly all modern desktop computers are modular, meaning that the components can easily be replaced or upgraded.
The hardware in a desktop computer is modular, making it easy for someone with intermediate knowledge of a computer to modify one. Desktop computers have a separate monitor and case. User-input peripherals such as keyboards, mouse are attached to the case, as well as other peripherals such as printers. Most of the functionality is contained within the case, but some components can be either external or internal (such as various storage devices or modems). The case is often placed on or under the desk. Sometimes, it can be placed underneath the monitor.
Desktop computers are generally cheaper than notebook computers. This is because no extra effort is needed to miniaturize the components, or manufacture components that use up less power. However, desktop computers do use up more power than notebook computers.

Laptop

A laptop (also known as a notebook) is a personal computer designed for mobile use. A laptop integrates most of the typical components of a desktop computer, including a display, a keyboard, a pointing device (a touchpad) and speakers into a single unit. A laptop is powered by mains electricity via an AC adapter, and can be used away from an outlet using a rechargeable battery. A laptop battery in new condition typically stores enough energy to run the laptop for three to five hours, depending on the computer usage, configuration and power management settings.
Laptop computers generally cost more than desktop computers with the same capabilities because they are more difficult to design and manufacture. Laptops usually come with displays that use thin-screen technology. The thin film transistor or active matrix screen is brighter and views better at different angles than the STN or dual-scan screen. Laptops use several different approaches for integrating a mouse into the keyboard, including the touch pad, the trackball, and the pointing stick. A serial port also allows a regular mouse to be attached. The PC Card is insertable hardware for adding a modem or network interface card to a laptop. CD-ROM and digital versatile disc drives may be built-in or attachable.

Palmtop Computer

A palmtop computer is a very small computer which you can hold in one hand and manipulate with the other.These kinds of computers have specialized keyboards or keypads to enter data, or small QWERTY keyboards. Other names for palmtops are handheld computers, pocket computers and PDA.
The main features of these computers are that they are small, light, draw power from a battery and are intended for general usage. Their input includes a typewriter keyboard and the output consists of a small, full-color LCD display. The palmtop has a word processor, a spreadsheet program, a calendar and a phone book.
An important characteristic is that its operating system is compatible with that of a PC. Various programs can be installed and run and the data may be transferred to and from a desktop computer. In contrast to personal digital assistant, it has more memory, a keyboard and many available programs. Handheld computers usually do not have disk drives due to their small size. They have PCMCIA slots where disk drives, modems, memory or other devices could be put into. Palmtops that do not use a keyboard but a pen are called PDAs or hand-held computers.

Classification of Computer :ACCORDING TO TECHNOLOGY

ACCORDING TO TECHNOLOGY

• Extended Technology (XT) computers
• Advanced Technology (AT) computers
• Personal System Second (PS/2) Computers.

a) Extended Technology or XT

The extended technology computers used 8006, 8008, 8086, 8088 processors. The period of these computers was from 1975 to 1982. These processors had 4.77 MHz clock speed. The processors were all of 8-bit. These computers are outdated now by two reasons: first, they do not support the latest software and the second that they had low processing power as well as low storage capacity.

b) Advanced Technology or AT

With the advent of 80286 computer microprocessors in 1982, Advanced Technology computers were introduced. The processors were of 8-bit and 16-bit. The computers using processors like 80286, 80386, and 80486 are the examples of such computers. Advanced Technology computers' period is from 1982 to 1995. With the features of higher speed and larger memory than the XT computers, they support latest versions of available software.
AT computers may have 80286 SX or 80387 DX, 80486 SX, 80486 DX or even Pentium (80586) processors. The AT computers support Co-processor that enhances the processing speed and capability of the main processor to perform large and computations within a short period.

c) Personal System or PS/2

With the advancement of Processors having high clock speed as well as high storage capacity IBM developed the second generation of personal computers in early 1990s, which used new refined architecture making the computers faster and more powerful than AT computers. The PS/2 processors used VLSI (Very Large Scale Integration) for chip fabrication and their clock speed range from 85 MHz to 1GHz. Generally, PS/2 Computers use 3.5 inch floppy disks and OS/2 operating System. PS/2 computers are widely used in general purpose computation such as word processing, Database Arrangement, Controlling accounts etc.

Classification of Computer :ACCORDING TO BRAND

ACCORDING TO BRAND

IBM PC

IBM Compatible

Apple's MAC Computer

According to brand there are three types of computers. IBM-PC, IBM Compatible and Apple/Macintosh.

a) IBM-PC

IBM-PC stands for Internation Business Machine-personal computer. IBM is undoubtedly the leading computer manufacturer of the world that was established in 1925 in the USA by Dr. Herman Hollerith. It started manufacturing mainframe computers in 1945 and thereafter started manufacturing mini- and micro- computers.
The microcomputers manufactured by IBM are called IBM-PC computers. These computers are reliable, durable and possess high speed processing capabilities.

b) IBM- Compatibles

The computers having the same architectural design and functional characteristics as that of IBM computers are called IBM compatibles. These computers can run all the software and can perform all the tasks that IBM computers can do. IBM-compatibles are cheaper than IBM computers and their parts are easily available in the market. Therefore, they are very popular in the world. In Nepal, most of the computers are IBM compatibles. Some of the IBM compatibles used in Nepal are Compaq, AST, Wang, ALR (Advanced Logic Research), etc.

c) Apple/Macintosh

Apple Computer, Inc., was established in late 1970s in the USA by Steven Jobs and Stephen Wozniak. The computers manufactured by the Apple had different architectural design and functional characteristics as compared to IBM computers, and were named Apple computers. These computers have their own software, made for them, that are GUI based, easy, user-friendly and efficient. These computers are popular and specially used in graphic design and desktop publishing.
Another brand of Apple computers is Macintosh. These computers are easy to handle and are available in different capacity, cost and models. Apple/Macintosh computers are used in Nepal for Desktop publishing and graphic design.
In 1994, Power Computing Corporation began marketing Macintosh-compatible computers, raising the possibility of new microcomputer market segment. Presently, Apple has about 8 percent of the market. IBM has about 28 percent and IBM Compatible have most of the rest.
A few years ago, Apple Computer, IBM and Motorola joined to develop the PowerPC chip, which enable Apple computers to run IBM applications and vice versa. Most Apple Macintosh computers and compatibles are based on this chip. IBM recently released its PowerPC chip machines. It is difficult to assess the implications of this chip on the desktop market. Intel countered with the Pentium Pro chip.

Classification of Computer :ACCORDING TO SIZE

ACCORDING TO SIZE

The Columbia Supercomputer at NASA

IBM z-series computer is about 6 feet tall

HP 2100 mini-computer

According to size, traditionally computers are divided in four categories, namely,

a) Super Computer

• Super computers are the fastest, most-powerful and most expensive computers.
• It has the ability to recover automatically from failures.
• It has the ability to support several Giga Bytes of RAM.
• Unlike conventional computers, which have a single processor to process one instruction at a time, supercomputers have multiple processors (or CPUs) that process multiple instructions at a time.
• Supercomputers are widely used in scientific applications such as aerodynamic design and simulation, processing of geological data.
• One of the most powerful supercomputers today is "The Cray-2" and Some others are CRAY 1, CRAY - MP, SX-2, HITAC S-300, etc.

b) Mainframe Computer

• A mainframe computer is usually slower, less powerful and less expensive than supercomputers.
• Very large in size with approximately 1000 square ft area.
• Mainframes process several million instructions per second (MIPS). More than 1,000 remote workstations can be accommodated by a typical mainframe computer.
• Mainframes are used by banks and many businesses to update inventory, etc.
• Many modern mainframes have multiprocessing capabilities.

c) Mini Computer

• These are also a general purpose computer, smaller than mainframe computer. Medium sized computer, occupying approximately 10 sq ft of area.
• They have slower operating speed, smaller backup storage, limited hardware and less memory than mainframes.
• Minicomputers are well adapted for functions such as accounting, word processing, data base management, statistical packages for social sciences
• More than 50 terminals and large storage capacity device than micro computers but smaller than mainframe computers. E.g. Prime 9755

d) Micro Computer

• A microcomputer is the smallest, least expensive of all the computers.
• Microcomputers have smallest memory and less power
• Microcomputers are also called personal computers.
• The most common type of microcomputer is a desktop computer, which is a non-portable personal computer.

Classification of Computer :ACCORDING TO USE

ACCORDING TO USE

Computers are also categorized according to use in three sub-categories.

a) Analog

• Analog computers measure physical quantities (e.g. Voltage, Pressure, Temperature, Speed etc.) and convert them to numeric values.
• These computers recognize data as a continuous measurement of a physical property. Their output is usually in the form of readings on dials or graphs.
• These computers are capable of solving differential equations.
• Analog Computers are used mainly for scientific and engineering purposes because they deal with quantities that vary constantly.
• These computers are mostly used in medical science.
• They give only approximate results.

b) Digital

• These computers are high speed programmable electronic devices that are capable of performing mathematical calculations, comparing values and storing the results.
• They are capable of recognizing data by counting discrete signals representing either a high ("On") or a low ("Off") voltage state of electricity.
• An array of 1s and 0s represent all the Special Symbols, Alphabets and Numbers.
• These computers are further sub-categorized into two:

a) General purpose digital computers

• Those Digital computers that are theoretically be used for any kind of application are called the General Purpose Digital Computers. Example can be cited as those computers used for payroll, graphs, analysis, accounting etc.

b) Special purpose digital computers

• These are those computers which are made and used for a specific task. These computers can be fixed permanently into the machine. For e.g processors that are installed in automobiles to control fuel braking systems etc.

c) Hybrid

• The best features of analog and digital machines are combined together to create hybrid computing system.
• They have the speed of analog computers and the accuracy of digital computers.
• They are usually used for special problems in which input data derived from measurements is converted into digits and processed by computer.
• E.g. of these types of Computer are: - Computer used in Hospital, Computer used in Jet-plane etc