In the last video, you saw one way we can initialize a string variable: by specifying the character to be stored at each index. This is time-consuming and error-prone, so C offers more convenient ways to initialize a string variable. Let's look at a few of them.

The first way is to provide an array initializer with each of the string's characters. If you do this, don't forget that the null terminator is a character, too. Be sure to allocate space for it.

In this example, 'text' is an array of 20 characters; the first five elements hold 'hello' and the remaining 15 characters hold '\0'. Initializing a string in this way causes all characters of the array after the text to be set to the null character.

The second way to initialize a string variable is to give the characters of the string in double quotes [highlight line 4]. This is really just an abbreviation for the array initializer version we just saw.
Again the first 5 characters are set to 'h', 'e', 'l', 'l', 'o' and the remaining 15 elements
of the array are set to '\0'. It is illegal for the initializer (the double-quoted portion) to be longer
than the size of the char array but it *is* legal for the array and the initializer to be the same
size. And this is a common source of bugs. If the initializer specifies a character for each position
in the array, then there is no room for the null terminator, so the compiler will not add one.

We can change the contents of string variables at any time. After all, they are just char arrays.

C also offers you a short-cut for declaring and initializing string variables. You are allowed to omit the array size completely.

When you do this, the compiler will allocate a char array with enough space for each character of the initializer plus one more character for the null-terminator. So in this example, text will become of char array of size 6.

Omitting the size in the declaration does NOT mean that the size of text can change during the execution of the program. Once the array is declared it is a fixed size.
When you do this, the compiler will allocate a char array with enough space for each character

The double-quoted initializer for string variables is easily confused with the syntax used to create string literals. A string literal is a string constant that cannot be changed.

Notice that text is now a pointer, not an array. In this context, "hello" is a string literal -- a string constant that cannot be changed -- and text points to the first character of that string.

Remember that 'hello' is constant. Trying to change the string like this will cause undefined behaviour at runtime. It's perfectly OK to change a string variable but not a string constant. Be careful to choose the appropriate initialization syntax depending on whether you want an initialized string variable or a string literal.