The science of how to build
compilers for computer
programming languages.
Most of it is a branch of
formal language theory, especially concerned
with the construction of efficient techniques for parsing and
translating computer languages, and the classes of languages that lend themselves to these techniques.
Most of it was was developed around 1965-1975; famous names include Donald Knuth,
Jeffrey Ullman, Alfred Aho.
A good source of acronyms such as LL(1) and LALR(1).