Typedef in C

Last Updated on: October 28th, 2023

This article is a continuation of the Series on the C programming tutorial and carries the discussion on C language programming and its implementation. It aims to provide easy and practical examples for understanding the C program. In our last article, we have seen the difference between the macro and inline functions in C programming. In this article, we are going to explain typedef in C Programming.

Typedef in C

Although typedef is thought of as being a storage class, it isn’t really. It allows you to introduce synonyms for types that could have been declared some other way.

In C programming, the typedef keyword is used to create user-defined data types. It allows programmers to assign an alternative name (alias) to existing data types, making the code more readable and manageable. Here’s the basic syntax for typedef:

typedef existing_data_type new_data_type;

For example, let’s say we have a structure called Person that stores information about a person:

struct Person 
{
    char name[50];
    int age;
};

To create an alias for this structure using typedef, we can do:

typedef struct Person Person;

Now, we can use Person as a new data type instead of struct Person. Here’s an example of how it can be used:

struct Person 
{
    char name[50];
    int age;
};

typedef struct Person Person;

int main() 
{
    Person p1;  // Declaring a variable of type Person
    strcpy(p1.name, "John Doe");
    p1.age = 25;
    
    printf("Name: %s\n", p1.name);
    printf("Age: %d\n", p1.age);
    
    return 0;
}

By using typedef, we simplify the code by directly referring to Person instead of struct Person.

The new name becomes equivalent to the type that you wanted, as this example shows.

typedef int aaa, bbb, ccc;
typedef int ar[15], arr[9][6];
typedef char c, *cp, carr[100];

/* now declare some objects */
/* all ints */
aaa int1;
bbb int2;
ccc int3;
ar yyy; /* array of 15 ints */
arr xxx; /* 9*6 array of int */
c ch; /* a char */
cp pnt; /* pointer to char */
carr chry; /* array of 100 char */

In our next article, Enum in C programming.

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