Lecture 5 - Structured Programming Language

Lecture 5 - Structured Programming Language

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  Structured Programming Concepts Md.Imran Hossain Showrov (showrovsworld@gmail.com) 5 1
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  Outline  Structured programminglanguage  Main features of Structured programming language  Unstructured programming language  Why C is structured programming language?
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  Structured Programming Language Structured programming was first suggested by Corrado Bohm and Guiseppe Jacopini. The two mathematicians demonstrated that any computer program can be written with just three structures: decisions, sequences, and loops.  In general, Structured programming can be seen as a subset or sub- discipline of procedural programming, one of the major programming paradigms. It is most famous for removing or reducing reliance on the GOTO statement.  In programing languages that use the Structured programming paradigm, we use of the structured control flow constructs of selection (if/then/else) and repetition (while and for) block to perform certain tasks within the program.  Structured programming is also known as modular programming.
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  Structured Programming  Thereare three main principles of structured programming: 1. Program Design using top-down or bottom-up approach. 2. Decomposition of program into components 3. Structuring of control flow
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  Main Features ofStructured Programming Language 1. Division of Complex problems into small procedures and functions. 2. No presence of GOTO Statement 3. The main statement include – If-then-else, Call and Case statements. 4. Large set of operators like arithmetic, relational, logical, bit manipulation, shift and part word operators. 5. Inclusion of facilities for implementing entry points and external references in program.
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  Unstructured Programming Language A programming language in which the entire logic of the program is written as a single continuous (nonstop or unbroken) block is called "unstructured Programming".  Program written by following this language is very difficult to modify and to debug
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  Difference between Structuredand Unstructured Programming Language  The main difference between structured and unstructured programming language is that a structured programming language allows a programmer to dividing the whole program into smaller units or modules. But in unstructured programming language, the whole program must be written in single continuous way; there is no stop or broken block.  Structured Programming language is a subset of Procedural Programming language. But in unstructured Programming language no subset exists.  Structured Programming language is a precursor to Object Oriented Programming (OOP) language. But another one is not.
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  Difference between Structuredand Unstructured Programming Language (cont..)  Structured Programming language produces readable code while Unstructured Programming language produces hardly readable code “spaghetti”.  Structured Programming language has some limitations while unstructured Programming language offers freedom to program as they want.  Structured Programming language is easy to modify and debug, while unstructured Programming language is very difficult to modify and debug.  Examples of Structured Programming language are C, C++; and example of unstructured Programming language are BASIC (early version), COBOL.
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  Why C languageis Structured Language?  In order to accomplish any task, C-language divide the problem into smaller modules called functions or procedure each of which handles a particular job.That is why C-language is also called as the structured programming language.The program which solves the entire problem is a collection of such functions.
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  Why C languageis Structured Language?  In C Programming when writing a program we add preprocessor directive #inclue <filename> , than functions like main() , then opening of braces { } , inside the braces there are two parts declaration of variables and execution of statements which is a step by step process and well structured so anyone in the first look can understand what codes are doing what in which section.  The structured programming languages allows the program to be splied into multiple blocks of execution.  In C, you can split the program into such named blocks called functions.  That is why it is called a structured programming language.
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  Features of CProgramming Language  Low Level Language Support  Program Portability  Powerful  Manipulation  High Level Features  Modular Language  Efficient Use of Pointers
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  Features of CProgramming Language (cont..)  The future of the C language is very secure.This is because the choice of programming language for any application depends on the nature of the application itself.  C has been around for many years and has a dedicated community of users.  It has also a lot of online resources, a clean syntax and is easy to learn and use. So it is safe to say that C isn't going anywhere.
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  Advantages of CProgramming  C Programs are efficient, fast and Highly Portable .  It can be written in one computer and can be run in another one without any modification .  It is easy for debugging, error finding, testing and maintenance because of structured programming.