Three forms of the C language main function

in the C language, Main () there are three forms of the function.

1 , no parameters

#include <stdio.h>int main (void) {   printf ("Hello world!\n");   return 0;}

2 , there are two parameters

The first parameter is the integral type ARGC argv , saved as a string with The corresponding parameters, such as the following example:

#include <stdio.h>int main (int argc, char* argv[]) {   int i = 0;   for (; i < argc; i++) {       printf ("%s\n", Argv[i]);   }   printf ("Hello world!\n");   return 0;}

3 , there are three parameters

ARGC and argv env= Value " , the parameter type is an array of pointers or a level two pointer, as in the following example:

int main (int argc, char* argv[], char* envp[]) {    int i = 0;    for (; Envp[i]! = ' + '; i++) {        printf ("%s\n", Envp[i]);    }    printf ("Hello world!\n");    return 0;}

Three forms of the C language main function