C语言strlen()函数

#include<stdio.h>
#include <string.h>  
int main(){  
char ch[20]={'j', 'a', 'v', 'a', 't', 'p', 'o', 'i', 'n', 't', '\0'};  
   printf("Length of string is: %d",strlen(ch));  
 return 0;  
}  

Length of string is: 10