C Primer Plus (5th Edition)

2.6. Typedef Names

A typedef lets us define a synonym for a type:

typedef double wages; // wages is a synonym for double typedef int exam_score; // exam_score is a synonym for int typedef wages salary; // indirect synonym for double

A typedef name can be used as a type specifier:

wages hourly, weekly; // double hourly, weekly; exam_score test_result; // int test_result;

A typedef definition begins with the keyword typedef, followed by the data type and identifier. The identifier, or typedef name, does not introduce a new type but rather a synonym for the existing data type. A typedef name can appear anywhere in a program that a type name can appear.

Typedefs are commonly used for one of three purposes:

• To hide the implementation of a given type and emphasize instead the purpose for which the type is used

• To streamline complex type definitions, making them easier to understand

• To allow a single type to be used for more than one purpose while making the purpose clear each time the type is used