Object-oriented programming

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Object-oriented programming, also called OOP, is a type of programming language model for writing computer programs. Before object-oriented programming, most programs were a list of instructions that acted on memory in the computer. Instead of a procedural list of actions, object-oriented programming is modeled around objects that interact with each other. Classes generate objects and define their structure, like a blueprint. The objects interact with each other to carry out the intent of the computer program.

Many design patterns have been written utilizing object-oriented programming principles for code reuse.

Example Code[change | change source]

This computer code is in the Python programming language.[change | change source]

class Human(object):
    def __init__(self, name, friend=None):
        self.name = name
        self.friend = friend
    def say_name(self):
        print("My name is "+self.name)
    def say_goodnight(self):
        if self.friend is None:
            print("Good night nobody.")
            print("Good night "+self.friend.name)

#create a new human object named stephen
stephen = Human("Stephen")
#create a human object named joe with stephen as a friend
joe = Human("Joe", stephen)

stephen.say_name() #shows 'My name is Stephen'
stephen.say_goodnight() #shows 'Good night nobody.'
joe.say_name() # shows 'My name is Joe'
joe.say_goodnight() #shows 'Good night Stephen'

This code is in Java. It does the same thing as the Python code above.

public class Human
    private String name = "unnamed"; // the name of this human
    private Human friend = null; // the human's friend
      * This "creates" a new Human
    public Human(String name, Human friend) {
        this.name = name;
        this.friend = friend;
    public Human(String name) {
        this.name = name;
        this.friend = null;
    public Human() {
        this.name = "unnamed";
        this.friend = null;
    public void sayName() {
        System.out.println("My name is " + this.name);
    public void sayGoodnight() {
        if (friend == null)
            System.out.println("Good night nobody.");
            System.out.println("Good night " + friend.name);
public class Main
    public static void main(String[] args) {
        //create a new human object named stephen
        Human stephen = new Human("Stephen");
        //create a human object named joe with stephen as a friend
        Human joe = new Human("Joe", stephen);
        stephen.sayName(); //shows 'My name is Stephen'
        stephen.sayGoodnight(); //shows 'Good night nobody.'
        joe.sayName(); // shows 'My name is Joe'
        joe.sayGoodnight(); //shows 'Good night Stephen'

This code is in C++. It does the same thing as the Java code above.

class Human {
    string name; // The name of this human
    Human *mFriend; // The human's friend

    // This "creates" a new Human
    Human(string Name, Human Friend) {
        name = Name;
        mFriend = &Friend;
    Human(string Name) {
        name = Name;
        mFriend = NULL;
    Human() {
        name = "unnamed";
        mFriend = NULL;

    void sayName() {
        cout << "My name is " << name << endl;

    void sayGoodnight() {
        if (!mFriend)
            cout << "Good night nobody" << endl;
        else {
            cout << "Good night " << mFriend->name << endl;
int main() {

    Human stephen = Human("Stephen"); //create a new human object named stephan
    Human joe = Human("Joe", stephen); //create a human object named joe with stephen as a friend

    stephen.sayName(); //shows 'My name is Stephen'
    stephen.sayGoodnight(); //shows 'Good night nobody.'

    joe.sayName(); //shows 'My name is Joe'
    joe.sayGoodnight(); //shows 'Good night Stephen'

    return 0;

Criticism of Object Oriented Programming[change | change source]

OOP has become popular, but many people criticize it.

Luca Cardelli wrote a paper titled 'Bad Engineering Properties of Object-Oriented Languages'.

  • Richard Stallman wrote in 1995, "Adding OOP to Emacs is not clearly an improvement; I used OOP when working on the Lisp Machine window systems, and I disagree with the usual view that it is a superior way to program."[1]
  • A study by Potok et al.[2] tells us that there is very little difference in productivity between OOP and procedural approaches.
  • Christopher J. Date said that comparing OOP to other things, especially how OOP and the other thing are related, is difficult because people don't agree on the meaning of OOP.[3]
  • Alexander Stepanov suggested that OOP gives a point of view that is limited as far as math, and called it, "almost as much of a hoax as Artificial Intelligence" [4][5]
  • Paul Graham, a successful internet salesman and programmer, has suggested that the purpose of OOP is to act as a herding mechanism which keeps average programmers in average organizations from "doing too much damage". This also slows down faster, better programmers who know how to do things in a more powerful and more compact way.. [1]

References[change | change source]

  1. "Mode inheritance, cloning, hooks & OOP (Google Groups Discussion)".
  2. http://www.csm.ornl.gov/~v8q/Homepage/Papers%20Old/spetep-%20printable.pdf
  3. C. J. Date, Introduction to Database Systems, 6th-ed., Page 650
  4. The AI Effect
  5. STLport: An Interview with A. Stepanov