Introduction to Automata Theory
Automata theory :
the study of abstract computing devices, or ”machines” Before computers (1930),
A. Turing
studied an abstract machine (Turing machine) that had all the capabilities of today’ s computers (concerning what they could compute).
His goal was to describe precisely the boundary between whata computing machine could do and what it could not do

Source  : http://www.univ-orleans.fr/lifo/Members/Mirian.Halfeld/Cours/TLComp/TLComp-introTL.pdf