Objects and Methods in C

If you want to think in an object-oriented style within C, there’s a fundamental idea:

a struct can represent state, and a set of functions can represent methods.

In this lesson you will learn:

• how to think of an “object” in C
• how to associate behavior with a structure
• how to better design functions that operate on an entity

State + behavior

State

struct Rectangle {
    float base;
    float height;
};

Behavior

float calculateArea(struct Rectangle r) {
    return r.base * r.height;
}

Where would the “method” be here?

In C, the method isn’t embedded within the structure like in native object-oriented languages.

But conceptually, calculateArea fulfills a similar role: it’s an operation propre to Rectangle.

Clearer design with pointers

void scale(struct Rectangle* r, float factor) {
    r->base = r->base * factor;
    r->height = r->height * factor;
}

Here the function directly modifies the state of the structure.

Summary

• in C, a struct can represent the state of an entity
• related functions can be thought of as its conceptual methods
• this approach helps design clearer and more organized software

Final idea

OOP in C isn’t about imitating foreign syntax, but about building a design where each entity has clear data and coherent operations on that data.