C library function strlen()

C library function strlen()

#include <stdio.h>
#include <string.h>
int main()
{
   char a[20]="Program";
   char b[20]={'P','r','o','g','r','a','m','\0'};
   char c[20];

   printf("Enter string: ");
   gets(c);

   printf("Length of string a = %d \n",strlen(a));

   //calculates the length of string before null charcter.
   printf("Length of string b = %d \n",strlen(b));
   printf("Length of string c = %d \n",strlen(c));

   return 0;
}

Output