Introduction to Programming Languages Where do we start to understand programming languages as a core concept of Computer Science? There are literally thousands of programming languages.

Artifact (1) Paradigms (5) DSLs GPLs Kind of machines/programs (2) Key elements of a machine /program(2)

Paradigms: Imperative Functional Logic Object Oriented Parallel

DSL = Domain Specific Languages: HTMLVerilogLogoMata RSMathematica ExcelSQLYAClexers GraphViz

GPL = General Purpose (Programming) Language: Fortran (John Backus) Lisp (John McCarthy) Scheme PTL Scheme Racket Cobol (Grace Murray Hopper) Algol60 (John Backus and Peter Naur) Algol68 Pascal (Niklaus Wirth) PL/I Prolog (Alan Colmerauer) C (Ken Thompson and Dennis Ritchie)C++ (Bjorne Stroustrup) Ada Perl (Larry Wall) Python (Guido van Rossum) Ruby (Yukihiro Matsumoto) Java (James Gosling)

Kinds of Machines/Programs: 1 VNM = sequential 2 Multicore/cluster = parallel

Two Keys Elements of a Machine/Program: State Computation What does this look like in a VNM? State is captured in an ordered array of addresses Computation is expressed via an ordered list of instructions

Two Keys Elements of a Machine/Program: State Computation What does this look like in a parallel programming environment? State is captured in unordered sets Computation is expressed in logic = unordered set of declarative rules, each being an unordered conjunction of predicates

Characteristics for Parallel and Distributed Platforms: No guarantees of order of execution and communication Set-oriented approach (SQL) vs batch dataflow approach (MapReduce) Architectures with loose control over ordering (disorderly programming) Data parallelism vs task parallelism MapReduce, threads, MPI(message passing interface) OPL(Our Pattern Language) patterns for parallel programming Boom(Berkeley Orders of Magnitude) – Bloom language – Bud DSL in Ruby

So, what are we going to focus on?