A Very Basic Introduction to Networking and the Internet

Outline

• Start at the beginning...
  • Storing documents
  • Another computer rears its head...
  • Problems with copy documents
• The network arrives
  • Uses of a network
  • Access to the network from outside
  • About names
• Summary and Review
• The Internet
  • What is the internet?
  • Uniquity, ubiquity
  • And email...
  • What exactly is the point of email?
  • A virus is not a virus

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Start at the beginning...

So, let us start with a person – we'll call her Janet – and her computer, which we shall call computer 1. Without going into details, just accept that computers can store data or information after it has been placed in them, by typing or otherwise. Present-day computers store information on a unit called the Hard Disk drive, or colloqially the hard drive. On the most common personal computers (or PCs) used today - called 'IBM compatibles' for historical reasons - the hard drive is referred to by a letter, invariably starting with the letter 'C' (again for historical reasons). Other types of computer do this part differently; the rest of the description will however apply universally. Machines can have more than one hard drive, so for a PC the second hard drive would be drive D, then the third E, and so on.

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Storing documents

Now, let us say that Janet has typed a letter, to her bank. She has typed many letters to her bank - often in desperation of any intelligent response - but leaving that aside, she has decided to keep all the letters to the bank together. So she has created the computer equivalent of a file folder (usually known as a folder or sub-directory), which she has named 'Letters to my bank'.

So far so good. Now, a month later, she looks for her letter - since she has had no reply and wants to send a copy with yet another letter of complaint. To find the letter she has to look in her computer. So she looks in the folder 'Letters to my bank' on her hard drive 'C' on her computer, computer 1 (Figure 1   ).

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Another computer rears its head...

Now let us say that her husband, Ray, also has a computer; since it is a second computer, we will call it computer 2 (Figure 2   ). How could Janet tell Ray where the letter to her bank is? She might say, 'it's on my computer', but since there is room for millions of documents on a present-day computer, this might not be of much help. A better description would be, 'it's on my computer, that is computer 1, on drive C, in the folder "letters to my bank"'. If she had to write it down, it might be written as:

'computer 1/C/Letters to my bank'

and this is a specification as to where to find the file.

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Problems with copy documents

Now, what if Janet wanted to give Ray a copy of the letter, so that it was also available on his computer? One way is to copy the file from her computer and move it to the other one, usually using what is called a floppy disk - these being moveable from one machine to another - where it can be read. This would work, but there are now two copies of the letter.

Let us imagine a company of fifty workers, each with a computer, each wanting and needing access to each other's letters. Every document would have to be copied to every machine, so that there would be 50 copies of each letter. This is clearly inefficient, and very difficult to manage. It gets even more complicated if, as is commonly the case, more than one person needs to work on the same document or report. How could the various copies be tied together after different people had made their input to them?

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The network arrives

Therefore, many years ago, the idea of a Computer Network was born. Back to Ray and Janet. If Janet wanted to give Ray access to a document stored on her machine, then all that was needed was to allow Ray's machine to access the hard drive on her machine. This requires, first, a wire to connect the two machines together, then a bit of jiggery-pokery (or software) to make the machine think the remote hard drive on Janet's machine was actually a second local hard drive, say drive 'D', on Ray's machine (see sketch in Figure 3   ). Then Ray could find the file, but its name would have changed slightly. From Ray's machine it would now be:

'computer 2/D/Letters to my bank'

'computer 1/C/Letters to my bank'

Both of these refer to the ONE copy of the letter on Janet's machine, and we could describe this as the original address of the document [NOTE 1] .

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Uses of a network

Let us go back to the company, with 50 employees. Let them install a network, connecting all the machines together. Now they can, if they wish, each give access to the documents on their machine (some, or all of them, as they choose) to some or all of the other employees, so only one copy of each document has to exist, and it is reasonably straightforward for many different people to make their special input to a single document (as long as they don't all want to do it at the same time).

Now, imagine that the company starts a new division for a new area of business, with ten employees, on another floor of the same building. These ten employees will also have their computers on a network, all of which works as described so far. But what if the managers want to communicate with the managers of the rest of the business? Well, what they need is an inter-network connection, nowadays abbreviated as an internet (see Figure 4   ).

This mainly involves making a physical connection between the two network systems; apart from that, everything continues much as before. However, it might be convenient to distinguish the two networks. Therefore the two networks could be named, for example as 'Old Company' and 'New Company'. The specification for a document would then include the network name, the computer, the drive and the folder, for example:

'New Company/computer 1/C/ Letters of complaint to our bank'

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Access to the network from outside

Not only that, but let's say Janet and Ray want to have access to some data on the company's computers. This can be arranged. All that is needed is to use the telephone. The computer cannot directly use the telephone without some sort of black box. The usual and cheapest sort of black box is called a 'MODEM' (which stands for 'modulator/demodulator') and one of these is needed at each end of the telephone line. Basically they whistle at each other and translate the whistles back and forth into letters and numbers. Using this, the network can be extended temporarily out to the calling computer. We then have another inter-network or internet between the home network of Janet and Ray and the company network (see Figure 5   ).

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About names

A note on computer names. Computer 1, computer 2 and so on is all very well for a few computers, but not with 50 or 60 or more. Numbers are hard for humans to remember, so networks allow computers to have names. Janet's computer might be called 'Janet' and Ray's 'Ray'. Thus, the document referred to above would now be

The computers themselves still use unique numbers to refer to each other, but associate a name with this number for human use. What if there was another person named Janet at the company? Well, her computer address might be:

'OldCompany/Janet/C/ Letters of complaint to our bank' which is different from

'Janet/C/Letters to my bank' so there is no problem in deciding which Janet is which.

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Summary and Review

1. (Some) people have computers
   

2. Computers have hard drives, which store data
   

3. Computers can be connected together in networks
   

4. In networks, hard drives are shared with other machines
   

5. This allows lots of machines to share a single copy of data – a letter, engineering drawings, accounts, music and so on.
   

6. Networks, computers, folders and documents are named
   

7. Computers however use numbers to identify the same information: they associate the numbers with names for human readability
   

8. Networks can be connected together in inter-networks, which is usually shortened to 'internets'
   

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The Internet

The Internet (with a capital 'I') is the network of all the networks; that is, the network of networks of networks. This was done so that:

1. Information can be shared, rather than endlessly duplicated
   

2. Computer users can communicate with each other using electronic mail systems or 'email'
   

3. More recently, so that companies can sell people stuff at very low cost overhead
   

It all started out as a non-commercial US government secure communication system, but when it became obsolete, it was handed over to commercial interests to run. It is ancient: it has been running since before the 1960's so do not believe the hype about 'new technology' – it is old, indeed obsolete for its original task (the US Government has moved to a much faster and more sophisticated system). I have been (intermittently) connected to the Internet since 1986.

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What is the internet?

Strictly, the Internet only includes all those computers that are permanently connected together (over special telephone company -supplied lines called 'leased lines'). Home users typically connect via a modem and are called 'dial-up' users. Thus, some company with a permanent connection to the other computers has to set up a whole lot of modems connected to their network (and so to the Internet) and the home user dials up the company to connect to the rest of the Internet. Note that this is a local phone call. The company (called an 'Independent Service Provider' or ISP) will also usually offer some other services. For example, electronic mail can only be delivered to a computer that is permanently connected to the Internet, so the ISP will reserve some space on their machines (which are usually known as 'Servers') for a mailbox for the home user, to which all email is delivered. When the home user connects via the telephone, then this mail is collected by their home machine (sometimes described as 'downloaded').

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Uniquity, ubiquity

All the machines on the Internet obviously have to be uniquely identifiable. This is done by giving each machine a unique numeric address. For the usual reasons, a name that makes sense to humans is associated with this numeric address (called officially a domain name). The standardised form of name is known as a 'Uniform Resource Locator' or URL, and is very like the addresses already mentioned, except it uses dots '.' instead of the slashes '/' shown so far. Mostly, people access data in a special form arranged for easy use, which is called 'hypertext', abbreviated as http. This data is identified as 'web' data, and since the web is now worldwide, it is referred to as the 'World-wide Web' or www. So, a typical 'website' (a computer that has documents available in web or 'www' form) might have the address

http://www.win2000mag.net/

meaning 'hyper text transfer protocol documents at the world wide web area of the computer called win2000mag', whereas a particular document on that site might be

http://www.win2000mag.net/Forums/Application/Thread.cfm

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And email...

If one wanted to send them an email, the address would be different; for example:

tcp@win2000mag.com or ip@win2000mag.com

which, you will note, does not use the 'WWW' prefix. this is not needed becuase email does not use the WWW format.

My computer has underlined all these addresses for me as I typed them; I didn't do it. This indicates that they are 'live': if I select them, my computer will dial up my ISP (if I permit), and through them connect me to the appropriate address. This is what 'hypertext' means; it jumps you automatically through (virtual) hyperspace to the selected destination. Think Star Trek. All the original Internet development people were Trekkies.

The last bit of the domain name specifies what and where the company or organisation is. 'com' is short for 'commercial', and (often) indicates an American company. As with the (British) Post Office, since the Americans invented the Internet, they don't bother with 'USA'. British companies, however, will have a name that ends in 'co.uk'. German ones would be 'co.de' (Deutschland). There are quite a few other endings: the name of a University ends in 'ac' for 'academic', for example, so my alma mater (University of North London) is

unl.ac.uk

which is a lot easier than remembering a number. Oxford University, you might guess, is: oxford.ac.uk

The BBC is bbc.co.uk while their (hypertext) web pages would be at http://www.bbc.co.uk

'net' as an ending indicates an organisation or company connected with networking.

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What exactly is the point of email?

Well, have you ever noticed how much a postage stamp costs now? And the price never seems to go down. A fax is an alternate way of sending written information, but if you want to send a fax from America to Australia or vice versa, then it is very expensive, since it involves a telephone call between the two.

Sending an email still involves the cost of a phone call, to the ISP. But the ISP is local – so the call charge is usually local. In a single minimum-charge telephone call, it is possible to send around 100 separate e-mails (depending on their size – let's say, 100 3-page documents). And the cost does not vary depending on where the email is going – all you pay is for the local telephone call.

Now you see why every savvy company has moved to email. If you deal with foreign customers, you can save, not hundreds, but thousands or tens of thousands of pounds/dollars/currency units each quarter on telephone calls, faxes and letters.

Not only that, the email will typically reach its destination in between a tenth of a second and a few seconds. So it is possible to exchange many communications a day, all at the same low cost.

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A virus is not a virus

Oh, and viruses? A computer virus is not a virus. It is a computer program. They are referred to as a virus because they reproduce themselves by attaching themselves to other programs, and sneakily getting the other program to make copies of them - which is a bit like how a real virus works. They are often written by 17-year-old idiots who think they are clever. Most viruses, as you would expect bearing in mind the people that write them, simply don't work.

The media get all excited about viruses and those who write them, because the media (on the whole) don't really know how computers work. They like to get people worked up about nothing, and coin special names for those who do understand and use computers - like 'hackers'  [NOTE 2]  or 'geeks' (from 'freaks' or 'freeks', with a slightly pimply implication).

Viruses cause very little trouble as long as one follows a simple guideline – be careful when someone you don't know either sends you something you didn't ask for, or wants to talk to you. Many people have understood this sort of guideline for, oh, several thousand years now. There's an old, old, saying:

Beware of geeks bearing gifs

And that, actually, is it.

Footnotes

 [Note 1] Here I've used one of the simplifications I mentioned earlier: the description is nearly correct, but not quite. It does however describe the general picture quite well

 [Note 2] A 'hacker' is actually someone who 'hacks code'. To 'hack code' is to write computer programs. Hackers wrote all the computer programs, including those you're using right now. Most real hackers would happily strangle the kids who write viruses...