Conversion of a context-free grammar to a pushdown automaton

Store the start nonterminal symbol on a stack. An epsilon transition nondeterministically replaces its top nonterminal symbol by a production rule right-hand side. A top terminal symbol can be removed only while consuming the same input symbol. With a protected stack bottom marker, enter a final control state when that marker is exposed. Requiring all input to have been read implements acceptance by final state. The stack records the unprocessed suffix of a leftmost derivation, proving equality of the recognized and generated formal languages.