4.2.3.1 Stacks

Question 1

What does pushing do in stacks?

Answer 1

Adds a new specified item to the top of the stack

Question 2

What does popping do in stacks?

Answer 2

Removes the item from the top of the stack.

Question 3

What does peeking mean in stacks?

Answer 3

Returns the value at the top of the stack but doesn’t remove it

Question 4

Write a pseudo-code algorithm for the Push operation to push a value stored in the variable ANumber onto the stack.

Answer 4

Function Push(StackArray, TopOfStackPointer, ANumber)
	IF TopOfStackPointer < 20 THEN
		StackArray[TopOfStackPointer] = ANumber
		TopOfStackPointer += 1

End Function

Question 5

Advantages / disadvantages of a stack being implemented using an array

Answer 5

Empty entries waste space // Maximum/fixed/static size
Used when the size of the stack /amount of data is known
Memory saved since no pointers

Question 6

Advantages / disadvantages of a stack being implemented using a linked list

Answer 6

Space used by pointers // more complex to program

Used when the size of the stack is unknown