#include <stdio.h>
#include <string.h>
main()
{
    char s1[20];
    int len;
    printf("\nEnter any string: ");
    gets(s1);
    len = strlen(s1);
    printf("\nLength of string: %d", len);
    getch();
}

 OUTPUT:

Enter any string: programming9.com

Length of string: 16

C Program to Find Length Of a String With out Using Strlen() Function