A programming language is a notational system for describing computation in a machine-readable computation in a machine-readable and human-readable form ~Louden
- 1GL: Machine Code Languages
- 2GL: Assembly Languages
- 3GL: Imperative/Procedural Languages
- 4GL+: Event-Driven and OOP Languages
Each generation is at a higher level of abstraction.
We divide 3Gl and 4GL Languages into different styles or methodologies of language known as PARADIGMS.
Programming Paradigms:
- Interactive/Procedural: program = algorithm + data, good for decomposition
- Functional: program = functions § functions, good for reasoning
- Logic Programming: program = facts +rules, good for searching
- Event-Driven: program = GUI + algorithms + data, good for visual development
- Object- orientated: program = objects + messages, good for modelling.
Fortran
1957, based on mathematical equations and functions.
Innovations:
- Symbolic notation for subroutines and functions.
- Assignments to variables of complex expressions.
- DO loops.
- Comments.
- Input/output formats.
- Machine-independent: works on any computer.
Successes:
- Easy to learn- high level
- Promoted by IBM- addressed large user base
- (scientific computing).
CORAL
Designed by a committee of the US computer manufacturers. Targeted business applications. Intended to be readable by managers.
Innovations:
- Separate descriptions of environment, data and process.
Successes:
- Adapted as de facto standard by US DOD.
- Stable standard for 25 years.
- Still the most widely used PL for business applications.
PROLOG:
- Originated at U. Marseilles int eh early 70's and compilers developed at Marseilles and Edinburgh in the mid to late 70's.
- Theorem proving paradigm
- Programs as set of clauses: facts, rules and questions.
- Computation by 'unification'.
Successes:
- Prototypical logic programming language.
