structures and unions

In C++, structures and unions are user-defined data types that allow you to store multiple data types together. Structures are versatile and commonly used for representing real-life objects, while unions share memory among their members, making them useful for memory-efficient programming.

Defining Structures and Accessing Members

A structure groups variables of different types under a single name. Each variable within a structure is called a member.

Syntax:

Example: Defining a Person structure and accessing its members.

In this example:

• We define a structure Person with members name, age, and height.
• person1 is an instance of Person. We assign values to its members and display them.

Array of Structures

An array of structures allows you to store multiple instances of a structure in a single array. This is useful for managing data sets, such as a list of people or products.

Example: Array of Person structures.

In this example:

• We create an array people of Person structures and initialize it.
• We then iterate through the array to display each person’s information.

Structures within Structures

Structures can contain other structures as members, allowing for more complex data representations.

Example: A Student structure that contains a nested Address structure.

In this example:

• Address is a nested structure within the Student structure.
• We access the nested structure’s members using dot notation.

Introduction to Unions

A union is similar to a structure, but its members share the same memory location. This means only one member can hold a value at any time, which can be helpful when conserving memory.

Syntax:

Example: Defining a union to store either an integer or a float.

In this example:

• When floatVal is assigned a value, it overwrites intVal as they share the same memory location.
• Accessing intVal after assigning to floatVal shows unexpected data because intVal no longer holds a valid value.

Key Differences between Structures and Unions:

• Memory Allocation: In a structure, each member has its own memory location, while in a union, all members share the same memory space.
• Usage: Structures are useful for representing records, while unions are helpful in memory-sensitive scenarios where only one value is stored at a time.

Enumerations (Enums)

An enumeration is a user-defined data type that assigns names to integral constants, making code more readable. Enums are commonly used to define a set of related constants like days of the week or error codes.

Syntax:

Example: Using an enum for days of the week.

In this example:

• The Day enum defines constants for each day of the week.
• We assign Wednesday to today and check if it matches Wednesday.

Benefits of Enums:

• Enums improve code readability by replacing magic numbers with meaningful names.
• They help in preventing invalid values by restricting variables to specific constants.