Lecture 3 – September 6

NOTE: Force 2.0.8 CAN be installed on a flash drive (contributed by Christine Jones)

Things about mini-language Core that are not specified by the BNF handout

• Does horizontal spacing matter?
• We don’t know how to key in not equal
• We don’t know whether variables in this language are initialized to 0 for us or if they just take the value in memory at that location.
• We don’t know how big an integer we can use in an assignment statement.
• We don’t know what the maximum length of a variable identifier is.

What can’t you do in mini-language Core?

• Can’t comment
• Can’t add an identifier following opening word program
• We don’t know if program, integer, else, end, while, loop, if , input, output, then are reserved words or predefined terms. (i.e. We don’t know if we can declare an identifier PROGRAM)
• You can’t test for greater than or equal in a single test.
• There is no way to output a string.
• This language has no subprogram capabilities so no recursion is possible
• This language doesn’t allow us any floating point numbers
• This language has no division operator.

http://www.nsc.liu.se/~boein/f77to90/c1.html - changes from FORTRAN 77 to FORTRAN 90

FORTRAN’s do loop problem - a Venus probe was lost because

DO 10 I = 1,7 was accidentally written as DO 10 I = 1.7

FORTRAN’s horizontal spacing –

MOTHER = 5; is identical to M OT HER = 5;

Criteria for languages selected for Programming Language conference

1. in use in 1967

2. still in use in 1977

3. had significant influence on the field of computing

Languages selected

ALGOL 60 - concepts (blocks) – formal notation for syntax

APL – “A Programming Language” - highly specialized mathematical uses -

APT – “A Programming Tool” - one of the earliest – specialized -

BASIC - simplest – wide educational use

COBOL 60 – business data processing

FORTRAN – “formula translation” – scientific programming

GPSS – “general purpose simulation system” – earliest of simulation languages

JOSS – first designed for interactive environment

JOVIAL – outgrowth of Algol 58

LISP – symbolic processing and artificial intelligence

PL/I – combination of business and scientific – really large language

SNOBOL – string processing

SIMULA – first of the object oriented languages – introduced concept of class

The basic difference between a function and a subroutine is that

Functions return a single value

Subroutines return zero, one or many values

In FORTRAN,

Functions return their value by assignment to the function name

Subroutines return their values through the parameter list