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
Syntax is away of writing program in any language (every language has its own syntax)

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.

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.

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++

6. A short history of programming languages (cont.)
Fourth-generation languages
Productivity tools (such as spreadsheets)
Visual languages : Delphi
Scripting languages : Perl
Expert systems shells
Network computing : Java

7. Low-level vs. High-level Programming Languages
Machine code
Assembly
High-level: (abstraction from the computer details)
Basic, C, Java, Pascal, C++, Perl, Python, …
Assembly is translated by assembler to machine code.

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

9. Examples (1/5) Fibonacci numbers How to program? 0,1,1,2,3,5,8,13
Fn = Fn-1 + Fn-2 , n>=2 F0 = 0, F1 = 1
How to program?
0,1,1,2,3,5,8,13

10. Examples (2/5) Functional: (Haskell)
fib 0 = 0 fib 1 = 1 fib n = fib (n-1) + fib (n-2)

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; }

12. Examples (4/5) Assembly: (in x86 using MASM syntax)
mov edx, [esp+8] cmp edx, 0 mov eax, 0 ret cmp edx, 2 mov eax, 1 ret push ebx mov ebx, 1 mov ecx, 1 lea eax, [ebx+ecx] cmp edx, 3 mov ebx, ecx mov ecx, eax dec edx pop ebx ret

13. Examples (5/5) Machine code
8B FA B C383 FA B C353BB B D FA BD98B C84AEBF1 5BC3

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

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
-Easy to write.
-Based on module and easy to maintain better than procedural.

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?
When building a programming language we should think of :
Is it easy for people to read and understand .
- Is the Program can be expressed with less code and with high level of abstraction without getting more complicated.

17. Translation Compilation Interpretation
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
The machine will interact with the program during execution.
- Difference between compiler and interpreter is that compiler will compile code directly into machine code such as add operation but in interpreter no (it needs some other program designed for the specific machine.

18. Trade-offs Compilation Interpretation
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
Differences between compilation and interpretation