In the simplest of terms,
one can imagine a company’s information system as
consisting of one or more databases with company information and some number
of employees who need to access them remotely.
In this model, the data are stored on powerful computers called servers.
Often these are centrally housed and maintained by a system administrator.
In contrast, the employees have simpler machines,
called clients, on their desks, with which they access remote data,
for example, to include in spreadsheets they are constructing.
(Sometimes we will refer to the human user of the client machine as the ‘‘client,’’ but it should be
clear from the context whether we mean the computer or its user.)
The client and server machines are connected by a network,
as illustrated in Fig. 1-1. Note that we have shown the network as a simple oval, without any detail.
We will use this form when we mean a network in the most abstract sense.
When more detail isrequired,
it will be provided.