C Program to convert string to lowercase by the use of strlwr() function

/*to use the strlwr()*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>>
int main()
{
    char str[80];
    printf("enter the string: ");
    gets(str);
    printf("string in lowercase: ");
    puts(strlwr(str));
    system ("pause");
    return 0;
}