`_tmain()` vs. `main()` in C : What's the Difference and When Should I Use Each?

_tmain() vs. main() in C

_tmain() and main() are both function signatures used to specify the entry point of a C program. However, there are subtle differences between them that can affect program behavior.

What is _tmain()?

_tmain() is a Microsoft-specific function signature that is not part of the C standard. It is primarily used when dealing with character sets, specifically the wide character set used in Unicode.

What is main()?

main() is the standard entry point of a C program as defined by the ISO C standard. It can have one of two signatures:

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

Difference in Character Handling

The main difference between _tmain() and main() lies in how they handle character input from the command line.

• _tmain() takes an array of wide character arrays (wchar_t*) as input. This is useful when dealing with Unicode strings.
• main() takes an array of regular character arrays (char*) as input. This is suitable for non-Unicode environments.

Behavior in Unicode Environments

In Unicode environments, such as those used by Windows, _tmain() is generally preferred over main() because it ensures proper handling of wide characters. By default, Windows compiles _tmain() as wmain(), which takes an array of wchar_t*.

Example in Unicode Environment

If you run the following code in a Unicode environment:

int _tmain(int argc, wchar_t* argv[])
{
    cout << "There are " << argc << " arguments:" << endl;

    // Loop through each argument and print its number and value
    for (int i = 0; i < argc; i++)
        cout << i << " " << argv[i] << endl;

    return 0;
}

You will get the expected output with arguments being printed correctly as wide character strings.

Cross-Platform Considerations

It is important to note that _tmain() is not portable across different operating systems. If your program needs to run on both Unicode and non-Unicode platforms, it is recommended to use #ifdef macros to define either main() or _tmain() depending on the target platform.

Summary

_tmain() is a Microsoft-specific function signature used for Unicode handling, while main() is the standard entry point in C . By understanding these differences, you can avoid potential errors when dealing with character sets and ensure cross-platform compatibility.

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