The reference language is a particular representation language for Algol 68, used and suggested by the Revised Report. All the code examples in the report are written using the reference language.
Implementations of the language are encouraged (but not strictly required) to use representations that are reasonably close to the reference language whenever possible.
The reference language prescribes a representation (typographical marks) for many of the symbols in the strict language, including the infinite set of TAX-symbols, but there is still some room for implementations to diverge in the following aspects:
brief-pragmat-symbol. Note that this does not apply
to the symbols letter-aleph-symbol and primal-symbols
for which no representation should exist out of the representation of
the preludes.
style-TALLY-letter-ABC-symbol and
style-TALLY-monad-symbols, and any terminal production of
STYLE other PRAGMENT item and other string item.
ABC that differs from the reference language, then the
resulting language is a variant of Algol 68. This happens in
translations of the reference language to different natural languages.