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Introduction to programming languages, Algorithms & flowcharts

Introduction to programming languages, Algorithms & flowcharts. What are Program and programming language?. Program : Set of instructions which a computer can “ interpret ” to solve problems, make calculations, perform tasks, etc.

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Introduction to programming languages, Algorithms & flowcharts

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  1. Introduction to programming languages, Algorithms & flowcharts Slides borrowed from Instructor: Wajih Alouini

  2. What are Program and programming language? • Program : Set of instructions which a computer can “interpret” to solve problems, make calculations, perform tasks, etc. • Programming Language : A formal language that is intended for the expression of computer programs Slides borrowed from Instructor: Wajih Alouini

  3. Why study programming languages? • Programming languages are important for students in all disciplines of engineering because they are the primary tools of the central activity of any science. Slides borrowed from Instructor: Wajih Alouini

  4. Why study programming languages? (cont.) • To improve your ability to develop effective algorithms and to improve your use of your existing programming language. • To increase your vocabulary of useful programming constructs. • To allow a better choice of programming languages. • To make it easier to learn a new language. Slides borrowed from Instructor: Wajih Alouini

  5. A short history of programming Languages 1950 : Numerically based languages. FORTRAN (55) • Business languages. COBOL(60) • Artificial intelligence languages. LISP, ALGOL(58) • LISP, FORTRAN (55) ALGOL • 1970 : PLs Ada, C, Pascal, Smalltalk • 1980 : Development of functional programming: ML, Miranda Object-oriented programming: Smalltalk, C++ Slides borrowed from Instructor: Wajih Alouini

  6. A short history of programming languages (cont.) • 90s: • Fourth-generation languages • Productivity tools (such as spreadsheets) • Visual languages : Delphi • Scripting languages : Perl • Expert systems shells • Network computing : Java Slides borrowed from Instructor: Wajih Alouini

  7. Low-level vs. High-level Programming Languages • Low-level: • Machine code • Assembly • High-level: (abstraction from the computer details) • Basic, C, Java, Pascal, C++, Perl, Python, … Slides borrowed from Instructor: Wajih Alouini

  8. Styles of Computer Programming • Procedural: procedures, routines, subroutines, methods, or functions • e.g. C, Pascal, Basic, Fortran • Functional • Mathematical functions • e.g. Lisp, Erlang, Haskell, ML, … • Object-oriented • e.g. C++, Java, Smalltalk • Rule-based (or Logic) : facts, rules • e.g. Prolog Slides borrowed from Instructor: Wajih Alouini

  9. Examples (1/5) • Fibonacci numbers • Fn = Fn-1 + Fn-2 , n>=2F0 = 0, F1 = 1 • How to program? • 0,1,1,2,3,5,8,13 Slides borrowed from Instructor: Wajih Alouini

  10. Examples (2/5) • Functional: (Haskell) • fib 0 = 0fib 1 = 1fib n = fib (n-1) + fib (n-2) Slides borrowed from Instructor: Wajih Alouini

  11. Examples (3/5) • Procedural: (C) • int fib(int n){ int first = 0, second = 1; for (int i=0, i<n; i++) { int sum = first+second; first = second; second = sum; } return first;} Slides borrowed from Instructor: Wajih Alouini

  12. Examples (4/5) • Assembly: (in x86 using MASM syntax) • mov edx, [esp+8]cmp edx, 0 ja @f mov eax, 0 ret @@: cmp edx, 2 ja @f mov eax, 1 ret @@: push ebx mov ebx, 1 mov ecx, 1 @@: lea eax, [ebx+ecx] cmp edx, 3 jbe @f mov ebx, ecx mov ecx, eax dec edx jmp @b @@: pop ebx ret Slides borrowed from Instructor: Wajih Alouini

  13. Examples (5/5) • Machine code • 8B542408 83FA0077 06B80000 0000C383 FA027706 B8010000 00C353BB 01000000 B9010000 008D0419 83FA0376 078BD98B C84AEBF1 5BC3 Slides borrowed from Instructor: Wajih Alouini

  14. Attributes of a good language • Ease of program verification • Proof of correctness, desk checking, test • Simplicity of semantic and syntax • Programming environment • Portability of programs • Cost of use • Program execution • Program translation • Program creation, testing, and use • Program maintenance Slides borrowed from Instructor: Wajih Alouini

  15. Attributes of a good language (another view: to make a software reliable, maintainable, efficient) • Reliability • Writability • Readability • Simplicity • Safety (no goto, no pointers) • Robustness (undesired events can be trapped, like arithmetic overflow, invalid inputs) • Maintainability • Factoring (modularity) • Locality • Efficiency Slides borrowed from Instructor: Wajih Alouini

  16. Issues for all Languages • Can it be understood by people and processed by machines? • although translation may be required • Sufficient expressive power? • can we say what needs to be said, at an appropriate level of abstraction? Slides borrowed from Instructor: Wajih Alouini

  17. Translation • Compilation • Translate into instructions suitable for some other (lower level) machine • During execution, that machine maintains program state information • Interpretation • May involve some translation • Interpreter maintains program state Slides borrowed from Instructor: Wajih Alouini

  18. Trade-offs • Compilation • lower level machine may be faster, so programs run faster • compilation can be expensive • examples: C (and Java?) • Interpretation • more ability to perform diagnostics (or changes) at run-time • examples: Basic, UNIX shells, Lisp Slides borrowed from Instructor: Wajih Alouini

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