Stacks

Question 1

What are stacks comprised of?

Answer 1

• A sequence of items
• A stack pointer

Question 2

On what kind of basis is date retrieved from a stack?

Answer 2

Last-In-First-Out

Question 3

What are the key operations of a stack?

Answer 3

• Push
• Pop
• Peek
• Test for empty stack
• Test for full stack

Question 4

What is a stack overflow?

Answer 4

An attempt is made to push more data onto the stack that it can store

Question 5

What is a stack underflow?

Answer 5

Occurs when a pop is attempted on an empty stack.

Question 6

What are the uses of stacks?

Answer 6

• Reversing sequences of items
• Maintaining “undo” lists in applications
• Maintaining a web-browser history
• Storing processor state (register values) when handling an interrupt

Question 7

Test if a stack is empty?

Answer 7

Check if the stack pointer is equal to -1

Question 8

Test if a stack is full?

Answer 8

Compare the stack pointer to the maximum size of the array (-1)

Question 9

Push an item onto a stack?

Answer 9

1. Check if the stack is full if not…
2. Increment the stack pointer by 1
3. Assign the pushed item to the element within stack indexed by the stack pointer

Question 10

Peeking a stack?

Answer 10

1. Check if the stack is empty, if not…
2. Save the item in element indexed by the stack pointer to a variable
3. Return variable

Question 11

Popping a stack?

Answer 11

1. Check if the stack is empty, if not…
2. Decrement the stack pointer
3. Return the item at the stack pointer + 1

Question 12

What is the call stack

Answer 12

-The call stack is an area of memory used to store data used by running processes and subroutines.

Question 13

How does call stack work?

Answer 13

• With each new function/subroutine call a stack frame is pushed onto the call stack.
• When a process completes, its stack frame is popped off the call stack and the previous process continues.
• Each stack frame contains local variables, parameter values and return addresses for each “open” subroutine within a process.
• Only the stack frame at the top of the stack is actively processed.

Question 14

What information does a stack frame contain

Answer 14

• local variables
• parameter values
• return addresses