---
title: "main: Program Startup"
ms.date: "11/04/2016"
f1_keywords: ["vc.main.startup", "_tmain"]
helpviewer_keywords: ["program startup [C++]", "entry points, program", "wmain function", "_tmain function", "startup code, main function", "main function, program startup"]
ms.assetid: f9581cd6-93f7-4bcd-99ec-d07c3c107dd4
---
# main: Program Startup

A special function named **main** is the starting point of execution for all C and C++ programs. If you are writing code that adheres to the Unicode programming model, you can use `wmain`, which is the wide-character version of **main**.

The **main** function is not predefined by the compiler. It must be supplied in the program text.

The declaration syntax for **main** is

```cpp
int main();
```

or, optionally,

```cpp
int main(int argc, char *argv[], char *envp[]);
```

## Microsoft Specific

The declaration syntax for `wmain` is as follows:

```cpp
int wmain( );
```

or, optionally,

```cpp
int wmain(int argc, wchar_t *argv[], wchar_t *envp[]);
```

You can also use `_tmain`, which is defined in TCHAR.h. `_tmain` resolves to **main** unless _UNICODE is defined. In that case, `_tmain` resolves to `wmain`.

Alternatively, the **main** and `wmain` functions can be declared as returning **void** (no return value). If you declare **main** or `wmain` as returning **void**, you cannot return an exit code to the parent process or operating system by using a [return](../cpp/return-statement-in-program-termination-cpp.md) statement. To return an exit code when **main** or `wmain` is declared as **void**, you must use the [exit](../cpp/exit-function.md) function.

**END Microsoft Specific**

The types for `argc` and `argv` are defined by the language. The names `argc`, `argv`, and `envp` are traditional, but are not required by the compiler. For more information and an example, see [Argument Definitions](../cpp/argument-definitions.md).

## See also

[Keywords](../cpp/keywords-cpp.md)<br/>
[Using wmain Instead of main](../cpp/using-wmain-instead-of-main.md)<br/>
[main Function Restrictions](../cpp/main-function-restrictions.md)<br/>
[Parsing C++ Command-Line Arguments](../cpp/parsing-cpp-command-line-arguments.md)