Tools

Construct Pushdown Automata

Step 1 — Select a Pushdown Automaton

  • In the left panel titled “Select a Pushdown Automaton,” click one of the example buttons (e.g., L = 0^n1^n, Balanced Parentheses, or Palindrome W C W^R).
  • After selecting, the main (center) panel will load the PDA and its step-by-step execution view.
  • The right panel (“Transition Explanation”) updates to show details for the chosen PDA.
  • Use the legend at the bottom-left to review symbols: Q, Σ, Γ, δ, q0, Z, F.

Step 1 — Select a Pushdown Automaton

Step 2 — Select an example and view the automaton

  • In the left panel, click one of the example PDAs.
  • The center panel loads the PDA diagram (states and transitions).
  • Use the Controls below the diagram to step through execution.

Step 2 — Select example and view automaton

Step 3 — Click the first step and observe the explanation

  • In the center panel, click the first available step (often labeled STEP 1 or Start).
  • The automaton highlights the corresponding state/transition.
  • The right-side Transition Explanation shows the details for this step (input symbol consumed, stack action, and current stack top).
  • The Execution Path below the diagram adds a summary line for this step.

Step 3 — Click STEP 1 and view Transition Explanation

Step 4 — Navigate through all steps (dynamic: STEP 1 … STEP N)

  • Continue with the step controls (Next/Previous or STEP buttons). The total number of steps depends on the selected example; it is not fixed.
  • After each step:
    • Check the Transition Explanation on the right for the current step’s δ-transition, input action, and stack update.
    • Watch the diagram highlight the active state/edge.
    • See the Execution Path grow with each step taken.
  • Keep advancing until the final step (often indicated as “Final” or when the machine reaches an accepting configuration). The right panel will show the final acceptance/termination message.

Step 4 — Click through all steps and view full explanations

Step 5 — Check the result

  • Read the final status in the right panel:
    • Accepted if the PDA ends in a state in F and satisfies the example’s stack condition (e.g., empty stack or Z0 at bottom).
    • Rejected otherwise.
  • Use Previous/Reset to review steps, try a new input, or select another example.