break-even point

n. In the process of implementing a new computer language, the point at
which the language is sufficiently effective that one can implement the
language in itself. That is, for a new language called, hypothetically,
FOOGOL, one has reached break-even when one can write a demonstration
compiler for FOOGOL in FOOGOL, discard the original implementation language,
and thereafter use working versions of FOOGOL to develop newer ones. This is
an important milestone; see MFTL. Since this entry was first written,
several correspondents have reported that there actually was a compiler for
a tiny Algol-like language called Foogol floating around on various VAXen in
the early and mid-1980s. A FOOGOL implementation is available at the
Retrocomputing Museum http://www.catb.org/retro/.