What Is the Difference Between struct and union in C?

Introduction

Structures and unions are user-defined data types in C that group different variables under one name. However, their behavior differs significantly…

struct

A struct allocates separate memory for each member. Example:

struct Employee {
    int id;
    char name[50];
    float salary;
};

union

A union shares memory among its members, so only one member can be used at a time. Example:

union Data {
    int i;
    float f;
    char str[20];
};

Key Differences