Tính độ dài chuỗi

/************************Length of string******************/
#include "stdio.h"
#include "conio.h"

long LengthOfString(char* s);

void main()
{
char s[] = "vncoding.net";
int len = LengthOfString(s);
printf("%d", len);
getch();
}

long LengthOfString(char* s)
{
int len = 0;
while(*s != NULL)
{
len++;
s++;
}
return len;
}