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;
         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;  


Here is a rather heavy example of typedef.


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

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Martin Leslie