14.2 Modelling networked computers
You met a block diagram showing a model of a communication system in Figure 8. In this model, a transmitter sends data into a network which conveys it to a receiver; but how does this model work when the transmitter and receiver are computers?
Sometimes the computer's user is communicating with another computer user, (for example when using an online 'chat' system). In that case we can consider the users and their linked computers as forming a communication system similar to that shown in Figure 8.
Sometimes, however, the computer's user is communicating with another computer (for example, when browsing a website). Figure 11 models that situation; the blocks are 'user', 'computer', 'network' and then another 'computer'.
To explore the model shown in Figure 11, I'll use the example of sending a message from your computer at home to an Oepn University FirstClass conference. FirstClass is the system used by the Open University to enable registered students to communicate online with teaching staff and fellow students by email and take part in online conferencing.