title: "Startup and Termination (C++)"

ms.date: "12/10/2019"

ms.assetid: c6568ee6-40ab-4ae8-aa44-c99e232f64ac

All C++ programs must have a `main` function. If you try to compile a C++ *.exe* project without a main function, the compiler will raise an error. Dynamic-link libraries and static libraries don't have a `main` function. Although `main` is the starting point of execution, but before a program enters the `main` function, all static class members without explicit initializers are set to zero. In Microsoft C++, global static objects are also initialized before entry to `main`. Several restrictions apply to the `main` function that do not apply to any other C++ functions. The `main` function:

- Cannot be overloaded (see [Function Overloading](function-overloading.md)).

- Cannot be declared as **inline**.

- Cannot be declared as **static**.

- Cannot have its address taken.

- Cannot be called.

If your source files use Unicode wide characters, 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 as follows:

int main();

int main(int argc, char *argv[], char *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`.

If no return value is specified, the compiler supplies a return value of zero. 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).

The arguments in the prototype

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

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

**Microsoft Specific**

Microsoft C/C++ startup code uses the following rules when interpreting arguments given on the operating system command line:

- Arguments are delimited by white space, which is either a space or a tab.

- The caret character (^) is not recognized as an escape character or delimiter. The character is handled completely by the command-line parser in the operating system before being passed to the `argv` array in the program.

- A string surrounded by double quotation marks ("*string*") is interpreted as a single argument, regardless of white space contained within. A quoted string can be embedded in an argument.

- A double quotation mark preceded by a backslash (\\") is interpreted as a literal double quotation mark character (").

- Backslashes are interpreted literally, unless they immediately precede a double quotation mark.

- If an even number of backslashes is followed by a double quotation mark, one backslash is placed in the `argv` array for every pair of backslashes, and the double quotation mark is interpreted as a string delimiter.

- If an odd number of backslashes is followed by a double quotation mark, one backslash is placed in the `argv` array for every pair of backslashes, and the double quotation mark is "escaped" by the remaining backslash, causing a literal double quotation mark (") to be placed in `argv`.

The following program demonstrates how command-line arguments are passed:

#include <iostream>

using namespace std;

int main( int argc, // Number of strings in array argv

char *argv[], // Array of command-line argument strings

char *envp[] ) // Array of environment variable strings

{

int count;

// Display each command-line argument.

cout << "\nCommand-line arguments:\n";

for( count = 0; count < argc; count++ )

cout << " argv[" << count << "] "

<< argv[count] << "\n";

}