Introduction to Structs in C++

Table of contents

1. What is a struct?
   1. Syntax
   2. Example: Defining and Using a struct
   3. Output
2. Passing struct to Functions
   1. Example: Passing by Value
   2. Example: Passing by Reference
   3. Example: Passing by Pointer
3. Using Pointers with struct
   1. Example: Pointer to a struct
   2. Output
4. Summary

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What is a struct?

In C++, a struct (short for “structure”) is a user-defined data type that allows grouping multiple variables of different types into a single entity. It is particularly useful for representing objects with multiple attributes.

Syntax

The basic syntax for defining a struct is as follows:

struct StructName {
    // Member variables
    Type1 member1;
    Type2 member2;
    // ...
};

Example: Defining and Using a struct

Here is an example of a struct representing a student:

#include <iostream>
#include <string>
using namespace std;

struct Student {
    string name;
    int age;
    float grade;
};

int main() {
    Student student1;

    // Assign values to the struct members
    student1.name = "Alice";
    student1.age = 20;
    student1.grade = 85.5;

    // Access and display the struct members
    cout << "Name: " << student1.name << endl;
    cout << "Age: " << student1.age << endl;
    cout << "Grade: " << student1.grade << endl;

    return 0;
}

Output

Name: Alice
Age: 20
Grade: 85.5

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Passing struct to Functions

You can pass a struct to a function in three ways: by value, by reference, or by pointer.

Example: Passing by Value

When passing by value, a copy of the struct is made:

#include <iostream>
#include <string>
using namespace std;

struct Student {
    string name;
    int age;
    float grade;
};

void displayStudent(Student s) {
    cout << "Name: " << s.name << ", Age: " << s.age << ", Grade: " << s.grade << endl;
}

int main() {
    Student student1 = {"Bob", 21, 90.0};
    displayStudent(student1);
    return 0;
}

Example: Passing by Reference

Passing by reference avoids copying and allows modifying the original struct:

void updateGrade(Student &s, float newGrade) {
    s.grade = newGrade;
}

Example: Passing by Pointer

Passing by pointer is another way to modify the original struct:

void updateGrade(Student *s, float newGrade) {
    s->grade = newGrade;
}

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Using Pointers with struct

You can create pointers to struct objects and access their members using the arrow operator (->).

Example: Pointer to a struct

#include <iostream>
#include <string>
using namespace std;

struct Student {
    string name;
    int age;
    float grade;
};

int main() {
    Student student1 = {"Charlie", 22, 88.0};
    Student *ptr = &student1;

    // Access members using the pointer
    cout << "Name: " << ptr->name << endl;
    cout << "Age: " << ptr->age << endl;
    cout << "Grade: " << ptr->grade << endl;

    return 0;
}

Output

Name: Charlie
Age: 22
Grade: 88

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Summary

• A struct groups multiple variables into a single entity.
• You can pass struct objects to functions by value, reference, or pointer.
• Pointers to struct objects allow efficient access and modification of their members.

For more details, visit the C++ Tutorial.