Object-Oriented Programming Traditional Procedural Programming
In traditional, procedural programming, data and functions
(subroutines, procedures) are kept separate from the data they process. This has
a significant effect on the way a program handles data:
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the programmer must ensure that data are initialized with suitable values before use and that suitable data are passed to a function when it is called
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if the data representation is changed, e.g. if a record is extended, the corresponding functions must also be modified.
Both of these points can lead to errors and neither support
low program maintenance requirements.
Objects
Object-oriented programming shifts the focus of attention to
the objects, that is, to the aspects on which the problem
is centered. A program designed to maintain bank accounts would work with data
such as balances, credit limits, transfers, interest calculations, and so on. An
object representing an account in a program will have properties and capacities
that are important for account management.
OOP objects combine data (properties) and functions
(capacities). A class defines a certain object type by defining both the
properties and the capacities of the objects of that type. Objects communicate
by sending each other "messages," which in turn activate another object's
capacities.
Advantages of OOP
Object-oriented programming offers several major advantages
to software development:
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reduced susceptibility to errors: an object controls access to its own data. More specifically, an object can reject erroneous access attempts
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easy re-use: objects maintain themselves and can therefore be used as building blocks for other programs
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low maintenance requirement: an object type can modify its own internal data representation without requiring changes to the application.
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