Chapter 15: Navigating Object-Oriented Programming in C

Navigating Object-Oriented Programming in C
C Programming

Welcome to Chapter 15, intrepid coders! Today, we’re stepping into a new frontier of our coding journey as we venture into the enigmatic but exciting realm of Object-Oriented Programming (OOP) in C.

Wait, what? Object-Oriented Programming in C? You might be scratching your head here. After all, isn’t C traditionally a procedural language? Yes, you’re right, but that doesn’t mean we can’t apply some of the principles of OOP in C. This chapter is all about showing you how. Buckle up!

The Odd Couple: OOP and C

Object-Oriented Programming is a paradigm centred on the concept of “objects” – data structures consisting of data fields and methods together. It’s a way of structuring and organizing code that allows you to think about problems in terms of real-world objects and their interactions.

C, on the other hand, is fundamentally a procedural language, focusing on the process rather than data, with functions and structured control commands like if-else and for loops at its heart.

Despite this apparent mismatch, we can mimic OOP in C by being creative with how we use its existing features.

Data Abstraction: Structs to the Rescue!

The most straightforward approach to object-oriented programming in C is by using structures (struct). While C does not inherently support classes like C++ or Java, struct can serve as a reasonable substitute.

A struct can group related variables under one name, much like how an object in OOP has properties. We can define struct types that encapsulate data fields and simulate methods through function pointers within these structures. This encapsulation brings us a step closer to true object-oriented design.

Encapsulation and Information Hiding

In OOP, the principle of encapsulation ensures that an object’s internal state is shielded from outside interference. While C does not provide direct support for private and public class members, we can achieve similar effects through careful struct design and the disciplined use of static functions and variables in our .c files.

Inheritance and Polymorphism: The Creative Use of Pointers

C does not directly support inheritance and polymorphism, two pillars of OOP. However, we can simulate these features by exploiting the language’s powerful pointer system. By using pointers to base struct types and embedding struct types within each other, we can model a form of inheritance. Polymorphism can be achieved through function pointers and carefully designed interfaces.

Navigating the Challenges

Implementing OOP in C is not for the faint of heart. It requires a deep understanding of the language and careful, disciplined coding. It can be easy to make mistakes, and debugging can be challenging. However, the reward is a design methodology that can lead to code that is easier to understand, maintain, and extend.

Embrace the Adventure

In the end, using OOP principles in C is like creating a sculpture with a chisel and hammer. It’s more labour-intensive than using modern power tools, and it requires skill and patience. But with perseverance, the resulting work is a testament to your craftsmanship.

In the next few posts, we’ll delve deeper into the techniques and tricks of implementing OOP in C. So stick around, fellow coding adventurers, as we boldly go where few C programmers have gone before!

So, keep coding, keep exploring, and most importantly, keep learning! Object-Oriented Programming in C is not a myth but a challenging adventure, ready for those daring enough to embark on the journey.

Example – 1

Object-Oriented Programming (OOP) is not inherently supported in C, unlike languages like C++ or Java, but certain aspects of OOP can be simulated. The example below demonstrates the concept of encapsulation, and it will mimic a class object with methods using C’s structs and function pointers.

Here’s a simple example of a “Car” object:


// Car "class"
typedef struct {
    int speed;
    int (*speedUp)(int);
    int (*applyBrake)(int);
} Car;

// Method definitions
int speedUp(int increment) {
    // Accessing the speed variable directly won't be possible in this case
    // Assume there's a way to access the specific Car instance's speed here
    return speed + increment;

int applyBrake(int decrement) {
    // Assume there's a way to access the specific Car instance's speed here
    return speed - decrement;

int main() {
    // Instantiate a Car object
    Car myCar;

    // Initialize properties
    myCar.speed = 0;

    // Link methods
    myCar.speedUp = &speedUp;
    myCar.applyBrake = &applyBrake;

    // Use methods
    myCar.speed = myCar.speedUp(20);
    printf("The car speed after speeding up: %d\n", myCar.speed);

    myCar.speed = myCar.applyBrake(10);
    printf("The car speed after applying brake: %d\n", myCar.speed);

    return 0;

Please note that, due to the nature of C, we can’t directly access the object’s data (speed in this case) inside the function as we would do in true OOP languages. There are ways around this, such as passing the object itself as a parameter to the function, but this starts to make the code more complex and less intuitive from an OOP perspective.

Example – 2

In an aerospace context, we can imagine a simplified scenario where we have an “Aircraft” object. This object might have properties like “altitude” and “speed”, and methods like “climb” and “descend”.

Here is how we might model this using C:

#include <stdio.h>

// Define the Aircraft "class"
typedef struct {
    int altitude;
    int speed;
    void (*climb)(struct Aircraft*, int);
    void (*descend)(struct Aircraft*, int);
} Aircraft;

// Method definitions
void climb(Aircraft* aircraft, int increase) {
    aircraft->altitude += increase;

void descend(Aircraft* aircraft, int decrease) {
    if(aircraft->altitude > decrease) {
        aircraft->altitude -= decrease;
    else {
        aircraft->altitude = 0; // Can't go below ground level!

int main() {
    // Instantiate an Aircraft object
    Aircraft myAircraft;

    // Initialize properties
    myAircraft.altitude = 0;
    myAircraft.speed = 0;

    // Link methods
    myAircraft.climb = &climb;
    myAircraft.descend = &descend;

    // Use methods
    myAircraft.climb(&myAircraft, 10000);
    printf("The aircraft altitude after climbing: %d feet\n", myAircraft.altitude);

    myAircraft.descend(&myAircraft, 5000);
    printf("The aircraft altitude after descending: %d feet\n", myAircraft.altitude);

    return 0;

This program creates an “Aircraft” struct, with altitude and speed as properties, and climb and descend as methods. The methods adjust the altitude of the aircraft. It’s a very simplistic model and doesn’t account for many of the factors a real aircraft would have to deal with, but it serves to illustrate how you might use C to write code in an object-oriented style.

Note how we had to pass the object itself (the Aircraft struct) as a parameter to the methods in order to modify its properties. This is a key difference between C and languages with built-in OOP support, and can make the code somewhat more difficult to read and write.


These examples are greatly simplified and may not fully demonstrate the true advantages of OOP. It’s also important to note that C was not designed with OOP in mind, and while it can mimic certain OOP features, it lacks the full power and integration of OOP concepts that languages like C++, Java, or Python provide. For projects that would truly benefit from OOP, it might be more advantageous to use a language that natively supports OOP.

That said, understanding how to implement these structures in C can give you a deeper appreciation of how OOP works under the hood and can provide additional tools for solving problems in C.

Chapter 15: Navigating Object-Oriented Programming in C
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