main() function in C

In C, main() function is the entry point of c program, It means, When a program runs, c compiler looks for main() function to execute c program, Without main(), C program cannot run. C program execution starts from main() function.

main() function returns value of type int to the Operating System to notify, weather program run successfully or terminated abnormally. It returns 0 or 1.

Return value	Description
0	Program run successfully
1	Program terminated abnormally

Syntax

<return_type> main()
{
  // Set of statements
  return value;
}

Example

int main()
{
//Statements
return 0;
}

return always comes at the end of main() function, before closing curly braces.

main() can also be used with void return type, but it is not a good programming practice.

main() is of three types on the basis of return type and argument.

1. main with return value and no argument.
2. main with no return value and no argument.
3. main() with Command Line Arguments.

main with return value and no argument

It is recommended practice to use main() with return type, in any c program, because it notifies operating system about program execution status. only int should be, used as return type of main() function.

Example

int main(){
//Statements
return 0;
}

main with no return value and no argument

It is not a good practice, because Operating system does not knows about program execution status. void is used as return type of main() function.

Example

void main(){
//Statements

}

main() with Command Line Arguments

In C, main() can accept inputs with command line arguments. It takes two arguments

int argc	It returns the argument count or number of argument passed to main(). It is the first argument.
char* argv[]	It is argument vector, which is a string array holds input from user. It is the second argument.

Syntax

int main(int argc, char* argv[]) {
//Statements
return 0;
}

Example

#include <stdio.h>

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

    // Prints the Argument count or number of arguments
      printf("Argument count is argc is %d\n", argc);

    // Print argument from argv
    for (int i = 0; i < argc; i++) {
        printf("%s \n", argv[i]);
    }

    return 0;
}