C Program Convert String Upper Case

/* C Program to convert
 given string into lower case
*/

#include <stdio.h>
#include <string.h>

int main()
{
   char str[100];
   
   printf("Please, input a string to convert to lower case\n");
   gets(str);
   
   printf("The string in lower case is: %s\n", strlwr(str));
   
   return  0;
}