N-Tier

An N-tier application program is one that is distributed among three or more separate computers in a distributed network. The most common form of n-tier (meaning 'some number of tiers') is the 3-tier application, in which user interface programming is in the user's computer, business logic is in a more centralized computer, and needed data is in a computer that manages a database.

The easy example is Server side, Application

program and client side are in single Machine. Services which is run on the Server program and allows clients to called over its HTTP (which communicates data through Network) .

Developers must realize there is more to programming than simple code. This series addresses the important issue of application architecture using an N-tier approach. The brief introduction to the theoretical aspects, including the understanding of certain basic concepts.How to create a flexible and reusable application for distribution to any number of client interfaces. Technologies used consist of .NET Beta 2 (including C#, .NET Web Services, symmetric encryption), Visual Basic 6, the Microsoft SOAP Toolkit V2 SP2, and basic interoperability [ability to communicate with each other] between Web Services in .NET and the Microsoft SOAP Toolkit. None of these discussions (unless otherwise indicated) specify anything to do with the physical location of each layer. They often are on separate physical machines, but can be isolated to a single machine.

For starters, this article uses the terms "tier" and "layer" synonymously. In the term "N-tier," "N" implies any number, like 2-tier, or 4-tier, basically any number of distinct tiers used in your architecture.