Welcome to the CIS Seminar Fall, 2006

Taking this for Credit You’ll do a ½ hour presentation (or you and a friend will do a 1 hour presentation). This presentation includes background and discussion in the wiki. You need to participate You need to attend every week.

Grading Presentation: 50% Participation & Attendance: 50%

About Your Presentation We will pick topics today if possible. You need to do background research (hint: Google doesn’t yet cover all information in the universe! Try the library …) You need to make a good wiki page, including discussion prompts or problems. You need to make good slides You need to practice! I will ask for a trial run at least 3 days before. If you’re not ready I’ll ask for more trial runs.

Scheduling History of programming languages (Prof Peterson) Haskell (Prof Peterson) Mathematica as a programming language (Prof Keck) Hindley-Milner Type systems (Daniel) Computer camp wrapup (Prof Peterson) Ruby on Rails (Tim) Internship report (Kate) Running CMT (Randy Spydell) Alex Chiang (HP) Tim Chamilard (UCCS) Gareth Eaton (DU) Eric Friedman (CNet) Kate's Dad (???) Amanda Tarr (Some crazy game company) Possible Student talks: C++ and templates, Prolog, Snobol / Icon,

This Term’s Theme Programming Languages!

A Brief History of Programming Languages Computer Science is unique in that no one language of expression has emerged to supplant all others. Most other disciplines have one "official" language: * standard music notation * standard math notation * standards for blueprints & technical descriptions

Why So Many Languages? What keeps computing from having one standard language that absorbs all others??

In The Beginning Computers were really expensive! Few programs. Just write everything in the native language of the machine. LDQ X FMP X CALCULATE X * X STO SUM LDQ Y FMP Y CALCULATE Y * Y FAD SUM X * X + Y * Y STO SUM STORE SUM Old IBM Assembly

The First Real PL: Fortran It soon became obvious that assembly was hard to write and hard to understand. Mathematicians wanted to use more familiar notation. A Fortran II example written by John Backus 1954

Fortran Innovations * Math notations (infix expressions) * Basic control structures: IF, DO loops, subroutines / functions * No real linker – "Common Blocks" were a substitute * Column oriented syntax (punched cards)

Lambda Calculus Strikes! Lisp was a language WAY ahead of it's time! John McCarthy proposed a language based on lambda-calculus and S-expressions (pairs). 1958

Lisp Innovations * Automatic Storage Management * Purely functional subset * Defined by a meta-interpreter * Syntactic simplicity * Single recursive structure type Lisp is still alive and well – nowadays it's called "Python"

Algol Algol = "Algorithmic Language" Algol was a language for both programming and formal description of algorithms. 1958

Contributions of Algol * First language with "Modern" syntax * A language of scholarly publication * Better "function call" mechanism – more descriptive * Led to Pascal and eventually Java * Adopted as the "machine language" by Burroughs

COBOL Cobol was a language designed to fill the needs of the business community (mathematicians and other shady academics were responsible for the other languages!) It was influenced by Grace Hopper's ideas in Flow-Matic. 1959

Pity the Cobol Programmer MULTIPLY B BY B GIVING B-SQUARED. MULTIPLY 4 BY A GIVING FOUR-A. MULTIPLY FOUR-A BY C GIVING FOUR-A-C. SUBTRACT FOUR-A-C FROM B-SQUARED GIVING RESULT-1. COMPUTE RESULT-2 = RESULT-1 **.5. SUBTRACT B FROM RESULT-2 GIVING NUMERATOR. MULTIPLY 2 BY A GIVING DENOMINATOR. DIVIDE NUMERATOR BY DENOMINATOR GIVING X.

Cobol Innovations * Extensive I/O capabilities * Natural language (why?) * Abandoned native numeric representation * Emphasized data layout (nested naming) This is the language that will not die. You could earn big $$$ becoming a Cobol programmer.

APL Ken Iverson was probably the first "mad genius" to design a programming that was completely unprecedented and unique. Good luck figuring this one out: 1962

APL Contributions * An amazing economy of expression * Extreme functional programming – many APL operators made it into Haskell * Explored the difficulty of introducing new symbols into the PL * Everyone knew about APL but nobody actually used it except crazy math dudes * Still alive as the "J" programming language

Simula Simula expanded on Algol to add objects, classes, methods, GC. It is the ancestor of object oriented programming Ole-Johan Dahl and Kristen Nygaard External Class Geometry; Geometry Begin ! Subclasses declared in the prefixed block: ; Point Class Color_Point(C); Character C; Begin... End; Rectangle Class Square; Begin... End; ! Variables declared in the prefixed block: ; Ref(Color_Point) A1; Ref(Point) C, D; Ref(Circle) K; Ref(Line) E, F; Ref(Rectangle) R1; Ref(Square) S1; ! Block body: ; C :- New Point(5,6); D :- New Point(20,30); A1 :- New Color_Point(3, 4, 'G'); K :- New Circle(10, C); E :- New Line(C, D); F :- X; K.Shift (1,1); R1 :- New Rectangle("Rec_R1", 5, 4); S1 :- New Square("Square_S1", 4, 6); S1.Show; End of prefixed block;

Simula * Simula was designed for discrete event based simulation – something that O-O does very well! * It took a long time for O-O ideas to hit the mainstream (C++)