
 pushdown automaton (Site not responding. Last check: 20071008) 
  Definition: A restricted Turing machine where the tape acts as a pushdown store (or stack, where only the latest element can be read), with an extra oneway readonly input tape. 
  Note: From Algorithms and Theory of Computation Handbook, page 2419, Copyright © 1999 by CRC Press LLC. 
  Algorithms and Theory of Computation Handbook, CRC Press LLC, 1999, "pushdown automaton", in Dictionary of Algorithms and Data Structures [online], Paul E. Black, ed., U.S. National Institute of Standards and Technology. 
 www.nist.gov /dads/HTML/pushdownautm.html (128 words) 
