The TYPEDEF keyword.

Every variable has a data type. typedef is used to define new data type names to make a program more readable to the programmer.

For example:

| main() | main() { | { int money; | typedef int Pounds; money = 2; | Pounds money = 2 } | }

These examples are EXACTLY the same to the compiler. But the right hand example tells the programmer the type of money he is dealing with.

A common use for typedef is to define a boolean data type as below.
Note: Recent C++ compilers have introduced a boolean datatype.

typedef enum {FALSE=0, TRUE} Boolean main () { Boolean flag = TRUE; }

And as a final example, how about creating a string datatype?

typedef char *String; main() { String Text = "Thunderbird"; printf("%s\n", Text); }

The main use for typedef seems to be defining structures. For example:

typedef struct {int age; char *name} person; person people;

Take care to note that person is now a type specifier and NOT a variable name.

As a final note, you can create several data types in one hit.

typedef int Pounds, Shillings, Pennies, Dollars, Cents;

Examples:

Here is a rather heavy example of typedef.

Notes:

I would expect to see 'typedef' in header files.