• Language Paradigms
• Overview of structured programming approach
• Object oriented programming approach
• Characteristics of object oriented languages
Language Paradigms
• Imperative Paradigm – Procedural Programming : C, Pascal, COBOL, FORTRAN etc.
• Applicative Paradigm– Functional Programming – LISP, ML.
• Rule-based Paradigm– Logic Programming :– PROLOG
• Object-Oriented Programming – C++, JAVA, SMALLTALK
Our focus here is on procedural and Object oriented Programming approach.
O-O is a different Paradigm
• Central questions when programming.
– Imperative Paradigm:
– What to do next ?
– Object-Oriented Programming
– What does the object do ? (vs. how)
• Central activity of programming:
– Imperative Paradigm:
– Get the computer to do something.
– Object-Oriented Programming
– Get the object to do something.
Procedural programming approach
In procedural approach,
• A program is a list of instruction(statements).
• When program in PL become larger, they are divided into functions(subroutines, sub- programs, procedures).
• A procedure/function does the particular task for which it is designed.
• Several functions are grouped into a modules.
• Several modules constitutes the large program.
Overview of structured programming approach
• Structured programming
– Also known as modular programming.
– A subset of procedural programming that enforces a top-down design model.
– In top down approach, developers map out the overall program structure into separate subsections to make programs more efficient and easier to understand and modify.
Overview of structured programming approach
• Structured programming uses control structures to control the flow of statement execution in a program.
• The control structures of a programming language let us combine individual statements into a single program entity with one entry point and one exit point.
• We can then write a program as a sequence of control structures rather than a sequence of individual statements.
Overview of structured programming approach There are three categories of control structures:
1. Sequence- Statements executes one after another in sequences.
2. Selection (Decision)- Conditional statements executes base on the test result return by conditional statement.
3. Iteration (Repetition) - Repeate same statement of group of statements multiple times as specified by the control structure.
Overview of structured programming approach
• A pictorial view of structured program.
– Data items are placed as global so that they can be accessed by all the functions freely.
– Each function may have their own data also called as local data.
• Emphasis is on doing things, (Algorithms)
• Large programs are divided into smaller program – function
• Most of functions share global data.
• Data move openly around system from function to function.
• Function transform data from one form to another
• Uses top-down approach for program design
• In large program, it is difficult to identify which data is used for which function.
• Global variable overcome the local variable.
• To revise an external data structure, all functions that access the data should also be revised.
• Maintaining and enhancing program code is still difficult because of global data. • Focus on functions rather than data.
• It does not model real world problem very well. Since functions are action oriented and do not really correspond to the elements of problem.
Object Oriented Programming
•A methodology of programming that
–
associates data structures with a set of operators which act upon it.
–
The fundamental concept is to combine or encapsulate both data (or instance variables) and functions (or methods) that operate on that data into a single unit- Object.
– Can model the real world problem representing objects.
– Supports encapsulation, abstraction, inheritance, polymorphism ,message passing to write programs efficiently.
– Examples of OOP languages : Simula, Smalltalk, C++, Python, C#, Visual Basic .NET and Java etc.
Generally in Object Oriented programming
• Emphasis is on data rather than procedures.• Programs are divided into objects.
• Data structures are designed such that they characterize the objects
• Functions and data are tied together in the data structures so that data abstraction is introduced in addition to procedural abstraction.
• Data is hidden and can’t be accessed by external functions.
• Object can communicate with each other through function.
• New data and functions can be easily added. • Follows Bottom up approach
Characteristics Object Oriented Programming
Object-oriented programming is a programming methodology characterized by the following concepts:1. Data Abstraction: problem solving via the formulation of abstract data types (ADT's).
2. Encapsulation: the proximity of data definitions and operation definitions.
3. Information hiding: the ability to selectively hide implementation details of a given ADT.
4. Polymorphism: the ability to manipulate different kinds of objects, with only one operation, using different entities in one operation.
5. Inheritance: the ability of objects of one data type, to inherit operations and data from another data type. Embodies the "is a" notion: a horse is a mammal, a mammal is a vertebrate, a vertebrate is a lifeform.
Advantages Object Oriented Programming
• Object oriented programming contributes greater programmer productivity, better quality of software and lesser maintenance cost. The main advantages are:– Making the use of inheritance, redundant code is eliminated and the existing class is extended.
– Through data hiding, programmer can build secure programs that cannot be invaded by code in other pats of the program.
– It is possible to have multiple instances of an object to co-exist without any interference.
– System can be easily upgraded from small to large systems.
– Software complexity can be easily managed.
– Message passing technique for communication between objects makes the interface description with external system much simpler.
– Aids trapping in an existing pattern of human thought into programming.
– Code reusability is much easier than conventional programming languages.
Disadvantages Object Oriented Programming
➢ Compiler and runtime overhead. Object oriented program required greater processing overhead – demands more resources.➢ An object’s natural environment is in RAM as a dynamic entity but traditional data storage in files or databases
➢ Re-orientation of software developer to object-oriented thinking.
➢ Requires the mastery in software engineering and programming methodology.
➢ Benefits only in long run while managing large software projects.
➢ The message passing between many objects in a complex application can be difficult to trace & debug.
Application areas of OOP languages
Applications of OOP have importance in many areas.➢ The most popular application of OOP, up to now has been area of user interface design such as Windows .
➢ Real Business systems are often much more complex attributes & behaviors .
➢ OOP can simplify such complex problem. The areas of application of OOP include
➢ Real time systems
➢ Simulation & modeling
➢ Object-Oriented databases
➢ Hypertext, hypermedia
➢ AI & expert system
➢ Neural Networks & parallel programming
➢ Decision support & Office automation system
➢ CAM/CAD systems
. ➢ Computer Based training and Educational Systems
OO languages vs Object Based Language
• Object Based Language are those having– Object Identity + support Encapsulation
– Not support Inheritance and dynamic binding
• Examples : Ada, Visual Basic etc.
• Object Oriented Languages-
– Described already
– e.g.
SMALLTALK, JAVA, C++ et.
O-O Principles and C++ Constructs
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