There are still a few data types in C that we have not discussed.
Actually, since C allows you to define new data types at will, no one
can ever cover all possibilities. We will only discuss the most
important examples.
enum
Type specifier for variables that can have a set of different values.
void
Type specifier for "empty" data.
volatile
Type qualifier for data that changes independently of the program.
const
Type qualifier for data that cannot change.
In addition, there are two data types called struct and
union that are so important, they have received their own
chapter. (See Data structures, for more information on
struct and union.)