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ALGOL 68R from RRE was the first ALGOL 68 subset implementation, running on the ICL 1900. Based on the original language, the main subset restrictions were definition before use and no parallel processing. This compiler was popular in UK universities in the 1970s, where many computer science students learnt ALGOL 68 as their first programming language; the compiler was renowned for good error messages.
Differences between Algol 68R and the Revised Report
Algol 68R was designed to implement a dialect of the language of the original report so there are many language differences compared to the revised report. Some of the more visibly obvious include:
- Loops do not end with OD, the loop body (probably an encloaed clause) follows DO, e.g. TO 10 DO BEGIN something; something else END
- The CASE conformity clause (used to get values out of a UNION) is significantly different.
- ELSF is used instead of ELIF.
- OUSE (contraction of OUT CASE) is not available.
- The mode COMPL is spelt COMPLEX.
There are many other differences, not all of which are syntatic.
Details of how to run Algol 68R under a George 3 emulator can be found at the links below. The emulator and Algol 68R can be run on a number of systems, including the Raspberry Pi.
Note that this software is strictly for non-commercial use.