Question

char p[4]={'h','g','y'};
cout<<strlen(p);

This code prints 3.

char p[3]={'h','g','y'};
cout<<strlen(p);

This prints 8.

char p[]={'h','g','y'};
cout<<strlen(p);

This again prints 8.

Please help me as I can’t figure out why three different values are printed by changing the size of the array.

Answer 1

strlen starts at the given pointer and advances until it reaches the character '\0'. If you don’t have a '\0' in your array, it could be any number until a '\0' is reached.

Another way to reach the number you’re looking for (in the case you’ve shown) is by using: int length = sizeof(p)/sizeof(*p);, which will give you the length of the array. However, that is not strictly the string length as defined by strlen.

As @John Dibling mentions, the reason that strlen gives the correct result on your first example is that you’ve allocated space for 4 characters, but only used 3; the remaining 1 character is automatically initialized to 0, which is exactly the '\0' character that strlen looks for.