 In the book, you see examples like this of a character array. You may be thinking, this looks like a lot of work. What if I had a much longer array? And quick, how many characters are in this array? Sure, C counts them, but as we noted in a previous video, we don't have access to that number. In this form, character arrays are, to be honest, not terribly useful. However, there is something you can do to make character arrays much more manageable. Let's return to the original character array. Each character in this array has a numeric value. Here's the trick. We're going to add an extra sentinel value to the end of our array. The character with the numeric value zero is called the null character, and it doesn't correspond to any printable character. To write the null character in C, you use backslash zero. With this sentinel value, you can write a while loop that counts until it hits the null character, and that will give you the number of useful characters in the array. When you write a double quoted string in C, the compiler adds that null character at the end for you. The null character at the end makes an array of characters into a C string, and we'll learn much more about manipulating these strings in a later chapter.