Procedural programming (prosedürel programlama in Turkish) paradigm is a subset of the imperative programming paradigm. Another famous paradigm under imperative programming is object-oriented programming (OOP) (nesne yönelimli programlama in Turkish) 1. C is a very good example of procedural programming. 2

Procedural programming is a paradigm based on the functional decomposition idea. Procedural programming reflects the divide-and-conquer approach.

Philip II of Macedon

Philip II of Macedon: “Did somebody say divide and conquer?” Origin

As programmers programming in C, we take the problem and break it down into smaller problems. Then we write C functions to solve each smaller problem. Finally, these C functions which solve a smaller part of the original problem are combined to solve the given original problem. Depending on the programming language, part of the program that solves the smaller problem can be called function (as in C), procedure, routine, subroutine, method, etc.

For example, let’s say that our problem is getting an integer from the user and printing true if the given value is divisible by 3 and false otherwise. Although this is a very simple example, we can divide it into sub-problems and write a C function for each sub-problem.

#include <stdio.h>

int get_input(){
    int x;
    printf("Please enter an integer: ");
    scanf("%d",&x);
    return x;
}

int isDivisibleby3(int a){
    return !(a%3);
}

int main(void) {
    int y;
    y = get_input();
    if (isDivisibleby3(y))
        printf("true\n");
    else
        printf("false\n");
}

As you can see, we write C functions (procedures) to get an integer from the user and check divisibility by 3. Then we call the functions from the main flow to solve the original problem. Calling procedures by controlling flow is the fundamental idea behind procedural programming. For example, get_input() asks the user to enter a number and returns that number. This is a part of the problem, getting a number from the user. The other function, isDivisibleby3(), solves another part of the problem: checking the divisibility of a number by 3. These two functions are completely independent of each other, and they are not aware of other’s existence. In main(), there are called in a logical order. This is the main motivation behind procedural programming: divide, conquer and build the solution.

Along with Procedural Programming, there are many programming paradigms like Object Oriented Programming (a kind of imperative programming), Functional Programming (declarative programming), etc. Notice that a programming language can support coding in multiple paradigms. For example, one can write C programming style C++ codes following procedural programming practices. However, C++ is a very well-known multi-paradigm language. C++ supports both object-oriented and procedural approaches. Furthermore, C++ supports some functional programming features 3. There is even a separate book for that. Most of the programming languages like C++, Python, and PHP are multi-paradigm languages though Python and Java are intended to use with an object-oriented approach than a procedural style. But we can say that some languages like Smalltalk are intended to use with a single paradigm. For example, Smalltalk is a pure object-oriented programming language.

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It is the language designer’s choice that a programming language will or will not support a certain paradigm. For a given language, programming in a supported paradigm is easier because the language is designed to support that paradigm. But this doesn’t mean that one can’t write a program in a not natively supported paradigm. For example, C is not an object-oriented programming language. But one can write C programs with an object-oriented approach. There is even a book for that!

Object-Oriented Programming With ANSI-C by Axel Schreiner

Object-Oriented Programming With ANSI-C by Axel Schreiner

Of course, if the main aim is programming with an object-oriented approach then C isn’t a good choice because this approach is not native in C. But you can make it work…

The imperative programming paradigm is a natural way of programming if we consider processor architectures. This is also true for procedural programming. All processors (including ancient ones) natively support routines (functions in C). Almost all processors have instructions like GOSUB (go to subroutine) or RET (return from subroutine). If we write an assembly code, that program will consist of (imperative) instructions and some subroutines (procedures). At the end of the day, programming in C is similar to programming in assembly but of course much easier.

🔗 Another similar post from asynx:

Compared to object-oriented programming, procedural programming is a more native way of programming considering computer architecture. However, as I said previously, this doesn’t mean that one is a better way of programming than the other. It solely depends on your needs.

🤓 Reading one more post from asynx?

In summary, C is a programming language that supports the procedural programming paradigm.

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