Linearly bounded automata (LBA) are a special class of
nondeterministic5.7 Turing machines which have two extra symbols in their
input alphabet, say 
and 
, which are
called the left and right endmarkers; the LBA can neither
overwrite these markers nor move left from or right from ;
therefore, it uses only a limited amount of tape. LBA accept exactly Type 1 or
context-sensitive languages
(Hopcroft and Ullman (1979, 225);
Salomaa (1973, 35))5.8.