Question

I have this code:

int main()
{
    char ch[15];
    cout<<strlen(ch)<<endl; //7
    cout<<sizeof(ch)<<endl; //15
    return 0;
}

Why does strlen(ch) give different result even if it is empty char array?

Answer 1

ch is a local variable and local variables are not initialized. So your assumption that it is an empty string is not correct. Its filled with junk. It was just a co-incidence that a \0 character was found after 7 junk characters and hence strlen returned 7.

You can do something like these to ensure an empty string-

char ch[15]={0};
ch[0]='\0`;
strcpy(ch,"");

Here’s a similar thread for more reading

Variable initialization in C++