ICS 313 Fundamentals of Programming Languages

1. ICS 313Fundamentals of Programming Languages Spring Semester 2004 - 2005 (042) King Fahd University of Petroleum & Minerals Information & Computer Science Department

2. Section 04, 10:00-11:15am UT, 24:250 • Instructor: Dr. Wasfi Al-Khatib وصفي الخطيب • Office: 22: 133-1 • Office Hours: UT: 9:00 - 9:50am and 2:30 – 3:30pm M: 3:00 - 4:00pm Or by appointment • Phone: 1715 • email: wasfi@ccse.kfupm.edu.sa • WebCT Page: http://webcourses.kfupm.edu.sa

3. Catalogue Description • Concepts of Programming Languages: Syntax and semantics, Data types, Control structures, Subprograms, Exception handling, Run-time storage management. Programming paradigms: Imperative, functional, logical, object-oriented and concurrent programming

4. Course Objectives • Outline the history and describe the rationale of different programming languages. • Describe grammar and syntax specifications and analyze their implementations. • Describe, analyze and use the various mechanisms in procedural languages; e g. data types, scope, control structures subprograms, etc. • Describe and use the major programming paradigms: Imperative, Functional, Logical and Object-Oriented. • Explain and describe how concurrency and exception handling are used in programming Languages

5. Text Book • Concepts of Programming Languages, By. R. Sebesta, 6th Ed, Addison Wesley, 2004.

6. Course Outline • Preliminaries • Evolution of the Major Programming languages • Describing Syntax and Semantics • Imperative Programming (Introduction to C) • Functional Programming • Logic Programming • Names, Bindings, Type Checking and Scopes • Data Types • Expressions and the Assignment Statements • Statement-Level Control Structure • Subprograms • Implementing Subprograms • Abstract Data Types

7. Grading Policy

8. Important Dates

9. Attendance Policy • Attendance will be checked each class. • Unexcused Absences Policies: • The first THREE absences are FREE of charge. • The fourth absence is worth – 3 points of your overall score (out of 100). • Each subsequent absence, up to the sixth absence, is worth -0.75 of your overall score. • The seventh absence will result in an automatic DN grade. • An unexcused absence can become an excused absence ONLY by an official letter from the Dean of Student’s office.

10. General Rules • Students are expected to be courteous toward the instructor and their classmates throughout the duration of this course. • All cell phones and pagers must be turned off during class and exams. • Assignments are due at the beginning of class. No late assignment will be accepted. Discussing questions among your classmates is highly encouraged. Copying solutions from each other is NOT permitted and will be considered CHEATING and will be dealt with accordingly.

11. Pop Quizzes • 10 minute • Each covers material given during the current lecture. • They require you to be attentive during class time as you will be subject at any point in time to answer a pop-quiz.

12. IMPORTANT RULE • ZERO-TOLERANCE for CHEATING.

13. Exam Policies • 24-Hour Policy: One has 24 hours to object to the score of an assignment, a pop quiz, or a major exam from the end of the class time in which the graded assignment/quiz/exam papers have been distributed. If for some reason you cannot contact me in person within this period, send me an email requesting an appointment. The email should be sent within the 24-hour time period. • Exams, assignments and pop-quizzes are generally CHALLENGING.

14. 1. Preliminaries

15. Reasons to study concepts of PLs • Increased capacity to express programming concepts • Improved background for choosing appropriate languages • Increased ability to learn new languages • Understanding the significance of implementation • Increased ability to design new languages • Overall advancement of computing

16. Programming Domains • Scientific applications • Business applications • Artificial intelligence • Systems programming • Scripting languages • Special purpose languages

17. What is a Programming Language • A programming language is

18. Programming Language Definition • Language Syntax • Grammar and punctuation. • Superset of legal languages. • Language Semantics • What the syntax means. • Restricts syntactically correct programs.

19. Computer Program Development Algorithm Human brains Problem Semantics Algorithm Translation Syntax Syntax Computer Program

20. Why Take This Course? • In order to graduate • True • False • Not necessarily • None of the above • Learning a new language depends on how many languages you learn • True • False • Not necessarily • None of the above

21. Programming Paradigms • Imperative • Program = Algorithms + Data • Functional • Program = Function o Function • Object-Oriented • Program = Objects + Messages • Logic • Program = Facts + Rules • Special-purpose

22. Imperative Programming • Oldest style of Programming • Algorithm is expressed as a sequence of instructions, e.g. assignment, looping, … • For example, assembly, Fortran, Algol, Pascal, and C.

23. Example in C • Finding the greatest common divisor between two elements #include<stdio.h> void main() { int x,y; printf("enter any two numbers"); scanf("%d %d",&x,&y); if(x<0)x=-x; if(y<0)y=-y; while(x!=y) x>y?(x=x-y):(y=y-x); printf("gcd of the numbers is %d",x); }

24. Functional Programming • Comes from traditional Mathematics. • Description of computation is based on the evaluation of functions or the application of functions to known values. • No notion of variables or assignment to variables! • Loops are replaced by recursion! • For example Lisp, Scheme, ML, Haskell.

25. Example in Scheme • Finding the greatest common divisor between two elements (define (gcd u v) (if (= v 0) u (gcd v (remainder u v))))

26. Object Oriented Programming • Based on class and inheritance • Instead of applying global functions to variables, “methods” associated with instances are invoked (message passing) • For example, C++, Java, Smalltalk, …

27. Example in C++ • Finding the greatest common divisor between two elements // gcd.cpp - long integer greatest common divisor class BadGcdArgumentsException{ }; long gcd(long a,long b) // Euclidean algorithm - returns 0 // if a and b are both 0. { long r; // First make sure everything is >= 0. if(a < 0) a = -a; if(b < 0) b = -b; // If both arguments are 0, throw an exception. if(a == 0 && b == 0) throw BadGcdArgumentsException(); // Otherwise the gcd of 0 and x is x. if(a == 0) return(b); if(b == 0) return(a); // Keep dividing until we get a zero remainder. The last // nonzero remainder is the gcd. while(b > 0) { r = a % b; a = b; b = r; } return(a); }

28. Logic Programming • Like functional programming, but through formal logic. • A program is a set of predicates, i.e. rules governing the problem. • Either the truthfulness of a given formula or the deduction of new formulae results from running a logic program. • For example, prolog.

29. Example in Prolog • Finding the greatest common divisor between two elements gcd(U,V,U) :- V=0. gcd(U,V,X) :- V>0, Y is U mod V, gcd(V,Y,X).

30. Special-Purpose Languages • Shell, Awk, Perl, Python • System administration • Program configuration • Postscript, Tex, RTF • Text and document setting • HTML, XML • Markup Language

31. Example in Perl # This script takes as input the desired output filename (without the extension) and the # number of input files. It is assumed that the input filenames are of the form 1.ps 2.ps ... # 99.ps and so on and so forth. It then combines all postscript files into one file with a .ps # extension. Finally, it will generate the pdf version of the postscript file. $Docs_Dir = 'C:\\Program Files\\ScannerU\\'; $OutputFile = $ARGV[0]; $NumOfInputs = $ARGV[1]; $FileList = ""; for ($i = 1; $i <= $NumOfInputs; $i = $i + 1) { $FileList = $FileList . $i . ".ps "; } chdir($Docs_Dir); system("gswin32c -dNOPAUSE -sDEVICE=pswrite -dBATCH -sOutputFile=" . $OutputFile . ".ps " . $FileList); system("ps2pdf -r720 " . $OutputFile . ".ps " . $OutputFile . ".pdf "); • Make up one pdf file from separate postscript files.

32. Language Evaluation Criteria • Readability • The most important criteria • Factors • Overall simplicity • Too many features is bad • Multiplicity of features is bad • Orthogonality • Makes the language easy to learn and read • Meaning is context independent • Control statements • Data type and structures • Syntax considerations • Writability • Factors • Simplicity and orthogonality • Support for abstraction • Expressivity

33. Language Evaluation Criteria (cont.) • Reliability • Factors • Type checking • Exception handling • Aliasing • Readability and writability • Cost • Categories • Programmer training • Software creation • Compilation • Execution • Compiler cost • Poor reliability • Maintenance • Others: portability, generality, well-definedness

34. Language Design Trade-offs • Reliability versus cost of execution • Writability versus readability • Flexibility versus safety

35. Layered View of a Computer

36. Implementation Methods • Compilation • Interpretation • Hybrid Implementation Systems

37. Compilation • Translate high-level program to machine code • Slow translation • Fast execution

38. Interpretation • No translation • Slow execution • Usually found in functional and logic-based programming languages.

39. Hybrid Implementation Systems • Small translation cost • Medium execution speed

40. Programming Environments • The collection of tools used in software development • UNIX • An old operating system and tool collection • Borland JBuilder • A PC environment for Java • Smalltalk • A language processor/environment • Microsoft Visual C++ • A large, complex visual environment