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Types of Application

Quality in a service or product is not what you put into it. It is what the client or customer gets out of it. – Peter Drucker

Let’s discuss a very high details of OSI model before start discussion on “Types of Application”

OSI Model: The Open Systems Interconnection (OSI) model is a product of the Open Systems

Interconnection effort at the International Organization for Standardization. OSI model consists of a layer

structure. The OSI network model layers are arranged here from the lower levels starting with the physical

(hardware) to the higher levels.

Each layer of the OSI model exists as an independent module.

1-Tier Application: 1-Tier applications are also called stand-alone or desktop applications. An

application that runs stand alone in a desktop or laptop computer. This type of application s having only

one layer (Presentation and processing layers both resides in it). This type of applications will store data

using file format on system hard disk drive or any other secondary storage drives like USB drive, CD drive

etc.

Examples of 1-Tier application: Notepad, MS-Word, Paint, Sang It, MS-Visio, Acrobat Reader, QTP etc.

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Types of Application

Quality in a service or product is not what you put into it. It is what the client or customer gets out of it. – Peter Drucker

2-Tier Application: In Two Tier or Client/Server application 2 layers like Client and Server is involved. The Client

sends request to Server and the Server responds to the request by fetching the data from it. The problem with the

Two Tier Architecture is the server cannot respond to multiple requests at the same time which causes data integrity

issues.

The Client/Server Testing involves testing the Two Tier Architecture of user interface in the front end and database

as backend with dependencies on Client, Hardware and Servers.

Examples of 2-Tier application:

C++ Oracle

VB SQL Server

Ruby MySQL

Etc.

3-Tier Application: In Three Tier Architecture or Multi Tier Architecture three layers like Client, Server and

Database are involved. In this the Client sends a request to Server, where the Server sends the request to Database

for data, based on that request the Database sends back the data to Server and from Server the data is forwarded to

Client.

The Web Application Testing involves testing the Three Tier Architecture including the User interface, Functionality,

Performance, Compatibility, Security and Database testing.

Examples of 3-Tier application: Web applications

Example Web Server

IIS

Java Web Server

Apache Web Server