[Overview][Types][Classes][Variables][Index] | Reference for unit 'CustApp' (#fcl)

# Reference for unit 'CustApp'

Custom application class

`uses`
`System,`
`sysutils,`
`Classes,`
`singleinstance;` |  | Single instance application support

## Overview

The CustApp unit implements the TCustomApplication class, which serves as the common ancestor to many kinds of TApplication classes: a GUI application in the LCL, a CGI application in FPCGI, a daemon application in daemonapp. It introduces some properties to describe the environment in which the application is running (environment variables, program command-line parameters) and introduces some methods to initialize and run a program, as well as functionality to handle exceptions.

Typical use of a descendent class is to introduce a global variable Application and use the following code:

    Application.Initialize;
      Application.Run;

Since normally only a single instance of this class is created, and it is a TComponent descendent, it can be used as an owner for many components, doing so will ensure these components will be freed when the application terminates.