What Is User Defined Data Type in C?

A User Defined Data Type in C is a way for programmers to create their own data types by combining multiple existing data types. This allows for more flexibility and control in programming, as well as the ability to create custom data structures that fit specific needs.

Why Use User Defined Data Types?

Using User Defined Data Types can greatly enhance the readability, organization, and reusability of your code. By creating custom data types, you can encapsulate related data and functionality into a single entity, making your code easier to understand and maintain.

Defining a User Defined Data Type

To define a User Defined Data Type in C, you need to use the struct keyword. A struct is a composite data type that allows you to group variables of different types together.

The basic syntax for defining a struct is:

struct struct_name {
    datatype1 variable1;
    datatype2 variable2;
    // ..
};

Note: The struct definition ends with a semicolon (;).

Example:

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

Creating Variables of User Defined Data Type

To create variables of the newly defined User Defined Data Type, you can simply use the struct name followed by the variable name:

Syntax:

struct_name.variable_name;

Example:

struct Person person1;

Accessing Members of a User Defined Data Type

To access the members (variables) of a User Defined Data Type, you can use the dot (.) operator:

Example:

struct Person person1;
person1.age = 25;

Nested User Defined Data Types

You can also create nested User Defined Data Types, where a struct can contain another struct as one of its members.

Example:

struct Address {
    char street[50];
    char city[50];
    char state[20];
};

struct Employee {
    char name[50];
    int age;
    struct Address address;
};

The typedef Keyword for User Defined Data Types

The typedef keyword is used to define an alias for a data type. It can be used with User Defined Data Types to create shorter and more readable type names.

Syntax:

#define NEW_NAME OLD_NAME;

Note:

The typedef keyword does not create a new data type, it simply gives an existing data type a new name.

Example:

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

In this example, the struct is defined and given the name “Person” using the typedef keyword. Now, instead of writing struct Person, we can simply write Person.

Conclusion

User Defined Data Types in C provide a powerful way to create custom data structures that can improve the readability and organization of your code. By encapsulating related data and functionality into a single entity, you can make your code more modular and easier to maintain.

With proper use of User Defined Data Types, you can write cleaner and more efficient code that is easier to understand, debug, and modify.