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[OOP - Lec 03] Programming Paradigms

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[OOP - Lec 03] Programming Paradigms

  1. 1. Programming Paradigms Muhammad Hammad Waseem m.hammad.wasim@gmail.com
  2. 2. Programming Techniques • The evolution of programming techniques is • to make programming languages more expressive • to develop complex systems more easily • There are different programming paradigms • Unstructured Programming • Procedural Programming • Modular & Structural Programming • Object-Oriented Programming
  3. 3. Unstructured Programming • Usually, people start learning programming by writing small and simple programs consisting only of one main program. • Here main program stands for a sequence of commands or statements which modify data which is global throughout the whole program. Main Program Data
  4. 4. Drawbacks of Unstructured Programming • This programming technique can only be used in a very small program. • For example, if the same statement sequence is needed at different locations within the program, the sequence must be copied. • If an error needed to be modified, every copy needs to be modified. • This has lead to the idea to extract these sequences(procedure), name them and offering a technique to call and return from these procedures.
  5. 5. Procedural Programming • With procedural programming, you are able to combine sequences of calling statements into one single place. • A procedure call is used to invoke the procedure. • After the sequence is processed, flow of control proceeds right after the position where the call was made. Main Program Procedure
  6. 6. Procedures • With parameters and sub-procedures (procedures of procedures) , programs can now be written more structured and error free. • For example, if a procedure is correct, every time it is used it produces correct results. • Consequently, in cases of errors you can narrow your search to those places which are not proven to be correct.
  7. 7. Procedure Program View Main Program Data Procedure 1 Procedure 2 Procedure 3
  8. 8. Modular Programming • Modular programming is subdividing your program into separate subprograms such as functions and subroutines. • With modular programming, procedures of a common functionality are grouped together into separate modules. • A program therefore no longer consists of only one single part. It is now divided into several smaller parts which interact through procedure calls and which form the whole program.
  9. 9. Modular Programming Program View Main Program(Also a module) Data Data1 Module 2 + Data Data2 Module1 +Data Data1 Procedure1 Procedure2 Procedure3 The main program coordinates calls to procedures in separate modules and hands over appropriate data as parameters.
  10. 10. Modular Programming • Each module can have its own data. This allows each module to manage an internal state which is modified by calls to procedures of this module. • Each module has its own special functionalities that supports the implementation of the whole program.
  11. 11. Structural Programming • Also structured programming • A subset of procedural programming that enforces a logical structure on the program being written to make it more efficient and easier to understand and modify. • Certain languages such as Ada, Pascal, and dBASE are designed with features that encourage or enforce a logical program.
  12. 12. Problems with Structured Programming • Many Functions access the same data, change in data may require rewriting of all functions. It makes program difficult to modify. • It makes a program structure difficult to conceptualize. • Arrangement of separate data and functions does a poor job of modeling things in real world.
  13. 13. Object-Oriented Programming • OOP is a technique in which programs are written on the basis of objects. An object is collection of data and functions. • The fundamental idea behind object oriented programming is to combine both data and functions into a single unit. Such a unit is called object. • Object is derived from abstract data type. • Object-oriented programming has a web of interacting objects, each house-keeping its own state. • Objects of a program interact by sending messages to each other. • OOP is based on real world modeling
  14. 14. Object-Oriented Programming Program View Object1 Data1+Procedures1 Data Data1 Object3 Data3 +Procedures3 Object2 Data2 +Procedures2 Object4 Data4 +Procedures4
  15. 15. Object-Oriented Programming • In object-oriented programming , instead of calling a procedure which we must provide with the correct handle, we would directly send a message to the object in questions. • Roughly speaking, • Each object is responsible to initialize and destroy itself correctly. • Consequently, there is no longer the need to explicitly call a creation or termination procedure. • Each object implements its own module.
  16. 16. Object Oriented Languages • C++ • JAVA • C# (C Sharp) • Many other

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