PDA   
Example 1: Hopcroft & Ullman's PDA for {ww^R : w in (a + b)*}
FINAL STATE // Final State or Empty Stack, this line is not case-sensitive
a b // Input Alphabet: alphabet is CASE-SENSITIVE
a b Z // Stack Alphabet: alphabet is CASE-SENSITIVE
Z // Stack Start Symbol
q0 q1 q2 // Machine states (strings): note: alphabet and states are CASE-SENSITIVE 
q0 // Start State
q2 // Set of Final States--can be empty, in which case language is empty or machine accepts by Empty Stack.
q0 \ Z q2 Z  // transitions: input state, tape symbol, stack symbol, output state, stack output
q0 a Z q0 aZ
q0 b Z q0 bZ
q0 a a q1 \
q0 a a q0 aa
q0 a b q0 ab
q0 b a q0 ba
q0 b b q0 bb
q0 b b q1 \
q1 b b q1 \
q1 a a q1 \
q1 \ Z q2 Z
end   // required, this line is not case-sensitive