Sturcture and Class

Slides version: lecture1_slides.html Website version: lecture1.html

• Recap: Structure
• What is a Class?
• Difference between Class and Structure
• VSCode Tutorial
• Lab 1: Hello Class

Recap: Structure

Example: Structures in C - GeeksforGeeks

// A variable declaration with structure declaration.
struct Point
{
    int x, y;
} p1; // The variable p1 is declared with 'Point'

// A variable declaration like basic data types
struct Point
{
    int x, y;
};

int main()
{
    struct Point p1; // The variable p1 is declared like a normal variable
}

How to Initialize/Modify a Structure

#include <iostream>

using namespace std;

// A variable declaration like basic data types
struct Point
{
    int x, y;
};

void init_point(struct Point &p);
void print_point(const struct Point &p);
void modify_point(struct Point &p);

int main()
{
    struct Point p1; // The variable p1 is declared like a normal variable

    init_point(p1);

    print_point(p1);

    modify_point(p1);

    print_point(p1);

    return 0;
}

void init_point(struct Point &p)
{
    p.x = 10;
    p.y = 20;
}

void print_point(const struct Point &p)
{
    std::cout << "(" << p.x << ", " << p.y << ")" << std::endl;
}

void modify_point(struct Point &p)
{
    p.x = 100;
    p.y = 200;
}

Output (in console):

$ ./a.out
(10, 20)
(100, 200)

What is a Class?

A user-defined datatype which groups together related pieces of information.

-- Introduction to C++ | Electrical Engineering and Computer Science | MIT OpenCourseWare

Example

• Point on a 2D plane
  • x-coordinate
  • y-coordinate

Definition of Class

class Point
{
public:
    // Data members
    int x;
    int y;

    // Member functions
    void init();
    void print();
    void modify();
};

Difference between Class and Structure

Definition

class Point                         struct Point
{                                   {
public:
    // Data members                 // Data members
    int x;                              int x;
    int y;                              int y;

    // Member functions                 // No Member functions
    void init();
    void print();
    void modify();
};                                  };
// Class usuallay don't use         // Structure usuallay use
// functions to manipulate          // functions to manipulate
// the data members                 // the data members
                                    void init_point(struct Point &p);
                                    void print_point(const struct Point &p);
                                    void modify_point(struct Point &p);

Usage

int main()                          int main()  
{                                   {
    Point p1;                           struct Point p1;

    p1.init();                          init_point(p1);

    p1.print();                         print_point(p1);

    p1.modify();                        modify_point(p1);

    p1.print();                         print_point(p1);

    return 0;                           return 0;
}                                   }

VSCode Tutorial

Lab 1: Hello Class