Cambridge ALGOL 68C

Cambridge ALGOL 68C is an implementation of ALGOL 68. Other implementations of ALGOL 68.

The ENVIRON and USING clauses.

These clauses are kind of the inverse of the #include found in the C programming language, or import found in Python. The purpose of the ENVIRON mechanism is to allow a program source to be broken into manageable sized pieces. Note that it is only necessary to parse the shared source file once, unlike a #include found in the C programming language where the include file needs to be parsed for each source file that includes it.

Example of ENVIRON clause

A file called mylib.a68:

BEGIN
   INT dim = 3; # a constant #
   INT a number := 120; # a variable #
   ENVIRON EXAMPLE1;
   MODE MATRIX = [dim, dim]REAL; # a type definition #
   MATRIX m1;
   a number := ENVIRON EXAMPLE2;
   print((a number))
END

Example of USING clause

A file called usemylib.a68:

USING EXAMPLE2 FROM mylib
BEGIN
  MATRIX m2; # example only #
  print((a number)); # declared in mylib.a68 #
  print((2 UPB m1)); # also declared in mylib.a68 #
  ENVIRON EXAMPLE3;  # ENVIRONs can be nested #
  666
END

Restrictions to the language from the standard ALGOL 68

• no algol68 FLEX and variable length arrays.
• MODE STRING implemented without FLEX.
• The PAR parallel clause was not implemented.
• nonstandard transput.
• others...

A translator/compiler for ALGOL 68C was available for the PDP-10 and System/360 as well as a number of other computers.

External links

• Cambridge Algol 68: on the historical roster of computer languages - includes 10+ publication references.
• A TRANSPORTATION OF ALGOL68C - PJ Gardner, University of Essex - March 1977 (From 370 to DECsystem-10)
• Running Algol68C on MVS - using an emulator