C Language Typedef Typedef for Structures and Unions


Example

You can give alias names to a struct:

typedef struct Person {
    char name[32];
    int age;
} Person;

Person person;

Compared to the traditional way of declaring structs, programmers wouldn't need to have struct every time they declare an instance of that struct.

Note that the name Person (as opposed to struct Person) is not defined until the final semicolon. Thus for linked lists and tree structures which need to contain a pointer to the same structure type, you must use either:

typedef struct Person {
    char name[32];
    int age;
    struct Person *next;
} Person;

or:

typedef struct Person Person;

struct Person {
    char name[32];
    int age;
    Person *next;
};

The use of a typedef for a union type is very similar.

typedef union Float Float;

union Float
{
    float f;
    char  b[sizeof(float)];
};

A structure similar to this can be used to analyze the bytes that make up a float value.