Programming Tutorials

typedef in C++

By: Stanley B.  

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

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