Two-tier, Three-tier and N-tier Architectures
Figure 2-3 gives an example of a 2-tier client-server architecture.
In a three-tier architecture the application program logic is split up between three computers. For example (see Figure 2-4),
the client handles the presentation logic.
an application server handles the application logic.
a database server handles the data storage and data access logic.
In an N-tier architecture more than three sets of computers are used (see Figure 2-5).