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Chapter 11: Problem 9

What is the difference between a union and a structure?

Short Answer

Expert verified
Answer: The main difference between a union and a structure in terms of memory allocation is that in a structure, each member has its own memory location and the size is the sum of the sizes of its members, while in a union, all members share the same memory location and the size is equal to the size of the largest member. This means that a union can only store one type of data at a time, while a structure can store multiple types of data simultaneously.

Step by step solution

01

Introduction to Union and Structure

Union and structure are both user-defined data types in various programming languages like C and C++. They are used to group together variables of different data types under the same name.
02

Structure Basics

A structure is a collection of variables of different data types grouped together under a single name. Each member of a structure has its own memory location, so the total size of a structure is the sum of the sizes of its members. To access the members of a structure, we use the dot (.) operator followed by the member name.
03

Union Basics

A union is similar to a structure in that it can also contain variables of different data types grouped together as a single entity. However, the key difference is that all members of a union share the same memory location. The size of a union is equal to the size of its largest member. To access the members of a union, we also use the dot (.) operator followed by the member name.
04

Key Difference: Memory Allocation

The main difference between a union and a structure is how they allocate memory. In a structure, each member has its own memory location and the size is the sum of the sizes of its members. In a union, all members share the same memory location and the size is equal to the size of the largest member. This means that a union can only store one type of data at a time.
05

Use Cases for Union and Structure

Structures are used when we want to group different data types together under a single name and access them individually. Unions are used when we want to store different data types in the same memory location and only need to store one of these data types at a time. Unions can be useful for saving memory, as they allocate memory efficiently by sharing the same space among all members.

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Most popular questions from this chapter

What will the following code display? enum { POODLE, BOXER, TERRIER }; cout << POODLE << " " << BOXER << " " << TERRIER << endl;

Rewrite the following statement using the structure pointer operator: *(*strPtr).num = 10;

Look at the following code. structure Rectangle { int length; int width; }; Rectangle *r; Write statements that A) Dynamically allocate a Rectangle structure variable and use r to point to it. B) Assign 10 to the structure’s length member and 14 to the structure’s width member.

Before a structure variable can be created, the structure must be _________.

Look at the following structure declaration. struct FullName { char lastName[26]; char middleName[26]; char firstName[26]; }; Write statements that A) Define a FullName structure variable named info B) Assign your last, middle, and first name to the members of the info variable C) Display the contents of the members of the info variable
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