How is the main function called in a 'c' language program?

Answer 1

There is no default argument to the main function in C. Every C program must have one (and only one) main function. The standard dictates that the main function may have either of the following definitions:

int main (void) {/*...*/}

int main (int argc, char** argv) {/*...*/}

The first version is used when your program does not require any command-line switches. Note that int main () is an acceptable declaration of the main function in both C and C++, but is not a valid definition in C. Note also that, in C, the return type may be declared void, but not in C++.

The second version is more common. The argc argument holds the count of all arguments in the argv array and is always at least one. The argv argument refers to an array of char pointers to null-terminated character arrays thus all arguments are strings. Thus the value 42 will be passed as the string "42".

The first element, argv[0], is always the fully-qualified path to the program executable (hence argc is always at least one). As well as allowing your program to determine its physical location upon the system, it allows your program to determine its given name even if the user has renamed your executable. This is useful when printing error messages.

Any additional arguments passed from the command-line will be found in elements argv[1] through argv[argc-1]. The final element, argv[argc], is always nullptr.

Answer 2

int main( void )

-its a default main function.

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

-The variable argc never holds a negative value.

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

-envp is pointer constant.it have string values.

• argc is greater than zero.
• argv[argc] is a null pointer.
• argv[0] through to argv[argc-1] are pointers to strings whose meaning will be determined by the program.

Answer 3

You will be surprised: it's main.