FOC Unit V: User Defined Data Types

 

User-Defined Data Types (UDDTs)

In C programming, a User-Defined Data Type is a data type created by the programmer to store multiple values of different data types together.
Common UDDTs:

• Structure (struct)
• Union (union)
• typedef
• enum

Structure (struct)

Definition

A structure is a user-defined data type that allows you to combine variables of different data types under a single name.

Why structure?

• To group related data
• Example: student information → roll number, name, marks

Syntax

struct structure_name {
    data_type member1;
    data_type member2;
    ....
};


Example
#include <stdio.h>

struct Student {
    int roll;
    char name[20];
    float marks;
};

int main() {
    struct Student s1 = {1, "Anisha", 85.5};

    printf("Roll: %d\n", s1.roll);
    printf("Name: %s\n", s1.name);
    printf("Marks: %.2f\n", s1.marks);

    return 0;
}
Features of Structure
Stores multiple values of different types
Each member has a separate memory
Total memory = sum of all members
Members are accessed using dot (.) operator
Memory Example
For struct Student:
int roll = 4 bytes
char name[20] = 20 bytes
float marks = 4 bytes
Total = 28 bytes