Synonyms for both fundamental and derived types can be defined using the typedef keyword. The following code illustrates the use of typedef:
typedef unsigned char BYTE; // 8-bit unsigned entity.
typedef BYTE * PBYTE; // Pointer to BYTE.
BYTE Ch; // Declare a variable of type BYTE.
PBYTE pbCh; // Declare a pointer to a BYTE
// variable.
The preceding example shows uniform declaration syntax for the fundamental type unsigned char and its derivative type unsigned char *. The typedef construct is also helpful in simplifying declarations. A typedef declaration defines a synonym, not a new independent type. The following example declares a type name (PVFN) representing a pointer to a function that returns type void. The advantage of this declaration is that, later in the program, an array of these pointers is declared very simply.
// Prototype two functions.
void func1();
void func2();
// Define PVFN to represent a pointer to a function that
// returns type void.
typedef void (*PVFN)();
...
// Declare an array of pointers to functions.
PVFN pvfn[] = { func1, func2 };
// Invoke one of the functions.
(*pvfn[1])();