If a = , then means intitutively that whenver the PDA is in state q with z on the top of the stack regardless of the current input symbol, it can nondeterministically for any i, ,

• go to state
• pop z off the stack
• push onto the stack, and
• leave its read-only head where it is.

State transition diagram : A PDA can also be depicted by a state transition diagram. The labels on the arcs indicate both the input and the stack operation. The transition for and is depicted by