DSA · Theory

Callback Queue

Theory

477/810

If you can teach Callback Queue using print jobs, you know it. If you only know the heading, you don’t.

Callback Queue order — meaning → enqueue / dequeue FIFO → one limit. Dumping ten features helps nobody.

Callback Queue exists so Zara can keep print jobs correct in a lab printer.

Callback Queue shows up in a lab printer. Name print jobs, not “a real-world scenario”.

Callback Queue trap — confusing front and rear. Zara loses marks for that every viva.

After Callback Queue, Zara should still remember confusing front and rear.

Close Callback Queue with — “If I skip it, print jobs goes wrong like this: confusing front and rear.”

Diagram

  front → [A][B][C] ← rear
  out ↑         ↑ in
       FIFO

Exam tip

Say Callback Queue in one breath, then enqueue / dequeue FIFO, then confusing front and rear.

from collections import deque

q = deque()
q.append(10)      # enqueue
q.append(20)
print(q.popleft())  # 10
print(list(q))

Callback Queue — queue is FIFO. deque.popleft() is O(1).