Around the world by electronic cabin trunk: Tim Nott demystifies the squawks and whistles that communicate personal E-mail messages over global networks

This article reached the Independent by electronic mail - E- mail for short. The words left my computer as a stream of 'bytes', one for each character, and a few seconds later were on the Independent's computer system several hundred miles away, ready for editing.

I could have typed it on double-spaced A4 and sent it by post, but that would have been slow, unreliable and would have given someone the unenviable task of retyping it.

Sending it on disk would be better, as it obviates retyping, but still slow - E-mail enthusiasts call conventional post 'snail-mail'. Faxing it would be near-instant, but would still need rekeying, or undergoing the horrors of optical character recognition.

The simplest, most direct way to exchange E-mail is over a 'local area network' or Lan. This is a collection of personal computers physically wired together, say in an office block or on a university campus. Sending E-mail to another user on the network depends on the software installed, but usually involves little more than choosing a recipient from an electronic address book, typing the message and activating the 'send' command.

The recipient will be made aware of incoming mail by its title appearing in a list on their screen, possibly augmented by flashing lights or ringing bells. Wide-area networks can extend this over multiple sites, so an employee of Megasoft UK, for example, can E-mail colleagues at the US headquarters just as easily.

To send mail out of a network, or from a stand-alone computer, you first need a modem. This is a thing that connects a computer to the telephone system, converting digital data from the former to the squawks and whistles understood by the latter. You then need to subscribe to an E-mail service, which acts as a central sorting office for its members. Two popular services are the London-based Compulink Information Exchange (Cix, pronounced 'Kicks') and Compuserve, which is US-based, but has branches worldwide.

Things get a little more complicated here, as E-mail is not delivered to your door. Instead, the system is rather like a PO box. Having dialled the service, after some strange noises from your modem and an even stranger screenful of technical preamble, you are prompted to 'log in', giving your user name and password.

On Cix, the former is whatever you chose to call yourself when you first joined - most people use some sort of contraction of their real name, but there is nothing to stop you calling yourself something more fanciful, such as 'barkingmad' or 'cyberwarrior'. This is the handle by which you are known to other users of the system - the 'name' of your electronic name and address.

Other systems, such as Compuserve, are not so accommodating as you are assigned a nine-digit number. Your password is a secret between you and the machine and prevents others gaining access to your private mail just as a PIN stops them getting access to your Access. Once accepted as persona grata, typing 'mail' will summon the mail service and tell you if there are any new messages waiting in your 'inbasket'.

To send a message, you type 'to (name)', then the message. When you send a message, a copy is stored in your 'outbasket', and you can examine this to see if your out-going messages have been read by their recipients. The disadvantage of this is that it is expensive to read and write messages 'on-line' - you are paying by the minute for both the service itself and the telephone call.

Most systems offer other services, such as public discussions or 'forums' and programs to download, so to cope with all of this, regulars use an 'off-line reader' (OLR). This lets you compose messages at leisure, in much the same way as you would wordprocess a letter, but without the agonising over fonts and formatting. When you have prepared your messages, the OLR goes on-line and automatically posts your out-going mail and retrieves incoming mail, which it stores on your hard disk prior to disconnecting.

Thus connection time is minimised and you can read your mail off-line. But what if you want to send E-mail to someone outside the network or not a fellow member of a particular mail service? To do this, your network or service must be joined to the Internet, the global information network, in order to support 'external' mail.

Before you run off screaming at mention of the I-word, this is undoubtedly the easiest aspect of it. You need no knowledge of Gophers, FTP, or other arcane rituals. All you need know is the user name and the 'site' they connect to - just like a postal address.

My name and address, for instance, is timn@cix. compulink. co. uk. The bit before the ampersand is my user name and the bit after is the Internet address of Cix. You send the message in much the same way as internal mail, but using the full address. What happens after that it is better not to know. Suffice it to say the Internet is not so much the 'Information Superhighway' hyped by the press and Clinton Administration, but more a maze of twisty diversions, rather like the M5 in the holiday season.

By the time your message reaches its recipient it will have grown, with all sorts of 'header' labels marking its passage around the world's computers, like a well-travelled cabin trunk. The overwhelming advantage of electronic mail is that when it works it is the most cost and time-effective way of sending words around - particularly with long documents. A 60-page document might take an hour to fax, but less than two minutes to E-mail.

Furthermore, for long-distance communication via the Internet, you pay only for the communication to your local service. An extension of the E-mail system, binary mail or 'binmail' means you can send data other than plain text. Wordprocessor or spreadsheet files in their native form and even print-quality pictures can be sent - something you cannot do by fax. This is straightforward over a network or mail service, but gets more complicated over the Internet, where a diploma in communications is an advantage, preferably worn with sandals and a straggly beard.

There are disadvantages, too. The Internet is not 100 per cent reliable, so you cannot be sure your messages have got through until the recipient sends acknowledgement. Messages can be sent anonymously, forged or possibly 'hacked' by third parties, so it is not appropriate for vital or confidential business communication.

There is no such thing as a universal directory - though both Cix and Compuserve maintain member directories of real names and user IDs - so it can be hard to find the address of someone. Furthermore, unlike the Post Office, the system does not permit errors. Spell an address slightly wrong on snail-mail and the letter will probably get through - on the Internet it will 'bounce'. Although network and same-service E-mail communications are immediate, the Internet is not; though most messages, if they are going to get through at all, will do so within an hour.

Finally, it is worth remembering that E-mail is not as ephemeral as it sounds, particularly on a local network. Copies of mail messages will remain on both the sender and recipient's disks - and possibly elsewhere on the system - until erased. Do not plot against your boss, or conduct a clandestine romance, over the office network. You will leave incriminating evidence in your wake.

Cix: 081 390 8446.

Compuserve: 0800 289458.

Jargon buster

Binary file: A file usually only readable by a program, often storing information in compressed form rather than a string of characters.

Bytes: One of the basic units of computing, roughly equivalent to the storage needed for one character or numeral.

Download: To load a data file or program into a computer from another computer linked on a network.

E-mail: Electronic mail, messages sent over a network.

Forum: Electronic systems usually divide up information and discussions into forums or conferences each covering a separate topic or subject.

Network: A group of computers interconnected by cables, telephone lines or other communications links. The simplest kind is a local area network or Lan, which directly links several computers in one location over cables.

Off-line: When a computer is linked but not actively connected to a network.

On-line: When a computer user is connected to another computer and able to communicate and interact directly with it .

Site: On messaging systems, an electronic address, rather than a physical location.