Move
Definition: Let xApay and xwqy be two configurations of a PDA, M, where
x, w Î G*, A Î G, p, q Î Q, a Î S È {e}, and y Î S*.
Let r = Apa ® wq Î R be a rule. Then,  M makes
a move from xApay to xwqy according to r, written as
xApay |– xwqy [r] or, simply,  xApay |– xwqy.
Note: if a = e, no input symbol is read
Rule: Apa ® wq
 Gist: A computational step made by a PDA
Configuration:
a
p
A
y
x
New configuration:
q
…
w
…
y
x
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