## Tcl8.6.0/Tk8.6.0 Documentation > Tk C API, version 8.6.0 > Tk_Main

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### NAME

Tk_Main — main program for Tk-based applications

### SYNOPSIS

#include <tk8.6/tk.h>
Tk_Main(argc, argv, appInitProc)

### ARGUMENTS

int argc (in)
  Number of elements in argv.

char *argv[] (in)
  Array of strings containing command-line arguments. On Windows, when using -DUNICODE, the parameter type changes to wchar_t *.

Tcl_AppInitProc *appInitProc (in)
  Address of an application-specific initialization procedure. The value for this argument is usually Tcl_AppInit.

### DESCRIPTION

Tk_Main acts as the main program for most Tk-based applications. Starting with Tk 4.0 it is not called main anymore because it is part of the Tk library and having a function main in a library (particularly a shared library) causes problems on many systems. Having main in the Tk library would also make it hard to use Tk in C++ programs, since C++ programs must have special C++ main functions.

Normally each application contains a small main function that does nothing but invoke Tk_Main. Tk_Main then does all the work of creating and running a wish-like application.

When it is has finished its own initialization, but before it processes commands, Tk_Main calls the procedure given by the appInitProc argument. This procedure provides a “hook” for the application to perform its own initialization, such as defining application-specific commands. The procedure must have an interface that matches the type Tcl_AppInitProc:

    typedef int Tcl_AppInitProc(
            Tcl_Interp *interp);

AppInitProc is almost always a pointer to Tcl_AppInit; for more details on this procedure, see the documentation for Tcl_AppInit.

Tk_Main functions much the same as Tcl_Main. In particular, Tk_Main supports both an interactive mode and a startup script mode, with the file name and encoding of a startup script under the control of the Tcl_SetStartupScript and Tcl_GetStartupScript routines. However it calls Tk_MainLoop after processing any supplied script, and in interactive uses events registered with Tcl_CreateFileHandler to process user input.

### SEE ALSO

Tcl_DoOneEvent

### KEYWORDS

application-specific initialization, command-line arguments, main program
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