We all know there exist 2 approaches to write a program – 1) Procedure oriented programming (POP) and 2) Object oriented programming (OOP).
You can write a program in either way but there are notable differences
between both approaches. These 2 approaches are the result of software
development evolution over many decades. Since the invention of
computer, many approaches and methods have been tried to write a
program. It includes methods like a) Top-Down programming b) Bottom-Up programming c) Modular programming d) Structured programming etc. The basic purpose or the basic aim of all these methods were same – “to make programming efficient”
– means to make the process of writing a complex program less harder,
bug free, easily understandable, easily expandable/modifiable etc.
In simple words, difference between POP
and OOP can be explained like this:- A programmer can handle the task of
developing a moderately complex program fairly well enough with POP
method. When the program gets even more complex or is of a highly
complex type; it would be difficult to write it efficiently using POP
method. The whole task of programming would get harder, will take more
time, more bugs, more time for debugging etc. In such a case OOP method
proves to be much more efficient than POP method. A highly complex
program can be developed much efficiently using OOP method. I hope you
got a general idea of the difference between both! There is no rule that
one should use a particular method to develop a program. Its upto
the discretion of the programmer. However in the software development
industry, they all follow OOP method as it facilitates collaborative
working. The main reason is code reusability. A
particular piece of code developed by one programmer can be reused any
number of times by any number of other programmers. This makes software
development much faster and efficient.
Let’s look at both of them in brief:-
Procedure Oriented Programming
The word “procedure” is the key element here to notice. It means “a set of procedures” which is a “set of subroutines” or a “set of functions“. We all know about “functions in C language”. ‘C’
is a procedure oriented language. In a POP method, emphasis is given to
functions or subroutines. Functions are a set of instructions which
performs a particular task. Functions are called repeatedly in a program
to execute tasks performed by them. For example, a program may involve
collecting data from user (reading), performing some kind of
calculations on the collected data (calculation), and finally displaying
the result to the user when requested (printing). All the 3 tasks of
reading, calculating and printing can be written in a program with the
help of 3 different functions which performs these 3 different tasks.
Structure of POP method
The problem with POP approach is its handling of data. POP approach gives no importance to data. By ‘data’ we mean the information collected from user, the new results obtained after calculations etc. If you are familiar with ‘C programming’, you may recollect “storage classes” in C. In C, a data member must be declared GLOBAL
inorder to make it accessible by 2 or more functions in the program.
What happens when 2 or more functions work on the same data member ? If
there are 10 functions in a program, all these 10 functions can access a
global data member. It is possible one function may accidentally change
values of this global data member. If this data member is a key element
of the program, any such accidental manipulation will affect the whole
program. It will be too difficult to debug & identify which function
is causing the problem if the program is really big.
Handling of data & functions in POP
One of the most important feature of C language is “structures“. If you are familiar with C, recall the way structure is declared in C using keyword struct.
Structure provides a way to pack together different data types into a
single entity. Programmer can pack together integer data, decimal point
data (float), array data type etc into a single entity using structure. Programming using “structure”
was first introduced by C language and this is the single best reason
for its wide popularity and acceptance. You know the reason? Structure
models real world requirements well into a computer program. The problem
with structures was that it handled only data. Structure do not allows
to pack together associated functions inside it along with data. All the
function to manipulate data members inside structure has to be written
separately inside a program. For this reason, a C program has an over
dependency on functions.
In POP method, a problem is viewed as a
sequence of tasks to be implemented like reading, performing
calculations, displaying results etc. All the tasks are analysed first
and later functions/procedures are developed to implement all these
tasks in a program.
Object Oriented Programming
An OOP method differs from POP in its
basic approach itself. OOP is developed by retaining all the best
features of structured programming method/procedural method, to which
they have added many concepts which facilitates efficient programming.
Object oriented programming methods brings in many features and I would
say it makes possible an entirely new way of approaching a program.
Let’s first keep in mind that OOP retains all best features of POP
method like functions/sub routines, structure etc.
1) The first feature that any programmer would talk about OOP is “data hiding”
facility. OOP gives lots of importance to data. Programmer can hide the
really important core data from external world using OOP method. The
basic concept of OOP revolves around a feature similar to structure in
POP, named as class in OOP. A class is a feature in OOP
which facilitates to pack together different data types along with
different functions that manipulate these data members of class. Data
members can be declared as private or public inside a class. To hide the data from external world, a programmer does it by declaring the data as private. Keep note that a class is really similar to structure in ‘C’.
Just like structure, a class packs together different things into a
single entity. The major difference between class and structure is with
functions. Structure does not allow to pack together data with functions
(structure deals with data only) whereas class allows to pack together data with its associated functions.
In addition there are differences like ‘data hiding’ using
private/public. Structure does not facilitates data hiding! We know in
structure, the structure members are accessed uing an entity called
structure variables. In OOP we use another entity named ‘object’ to access both data and functions inside a class. We call data or function inside a class as ‘class member‘. A class member can be accessed from external world (outside the class) using an object of the class only!
This feature of data hiding is called as “Data Encapsulation“.
Thus one of the major flaws of POP is solved in OOP. OOP ties the data
closely to a particular class and its objects. There is no need of
“global data types” as in POP and hence data will not flow freely around
the program. This makes sure there will be no ‘accidental modification’ of critical data.
2) Another important feature brought in by OOP is ‘code reusability‘.
This simply means, a piece of code written earlier in a program can be
used later. This is made possible by a feature of classes named “inheritance”.
By using inheritance, one class can acquire the properties of another
class. Let me try to explain this using an example. Take the case of a
“School Management System”. Initially the management decided to develop a
software focused on students only (no data of teachers). The programmer
made the software perfectly and while developing he had declared a
class dedicated for collecting personal details like
Name,Age,Sex,Address etc. After one year school management decides to
incorporate data of teachers to the software. The programmer can add
this extension within a small time as he can reuse many of the codes he
had written earlier by making use of “inheritance“. The
class personal details is of general nature (Age, Sex etc are same for
every person irrespective of student/teacher). Programmer can inherit
this class as such to a new one and add extension to this class with new
properties like ‘educational qualification’ of the teacher.
There are even more features for Object
oriented programming like Polymorphism (overloading of operators and
functions), dynamic binding etc. Those features will be discussed later
in coming chapters of C++ tutorial.
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