[Year 12 SofDev] Sample Exam Questions

[Mike Brookes]

Hi Mark et Al

For the question to make sense one has to make the assumption that the 
stack positions start at the bottom with position zero and go up to 
position 4 which is the top of the stack. At the start the bottom two 
(in bold on the PDF) are valid, hence the top of stack pointer showing 1.

Below is the completed table and the stack at the start and after each step:

	
	
	
	
	
	
	
	
	
	
	
	
	

	
	
	
	
	
	
	Stack at start and after each step
Step 	Function 	Top 	Output 	
	
	
	Start 	Step 1 	Step 2 	Step 3 	Step 4 	Step 5 	Step 6
1 	Push (23) 	2 	Item added (23) 	
	Stack position 	4 	92 	92 	92 	92 	92 	92 	92
2 	Push (18) 		Item added (18) 	
	3 	75 	75 	18 	18 	75 	75 	75
3 	Pop 	2 	Item removed (18) 	
	2 	23 	23 	23 	23 	23 	23 	23
4 	Push (75) 		Item added (75) 	
	1 	83 	83 	83 	83 	83 	83 	83
5 	Push (92) 	4 	Item added (92) 	
	0 	52 	52 	52 	52 	52 	52 	52
6 	Push (47) 		Stack full 	
	
	
	
	
	
	
	
	
	

	
	
	
	
	
	Top 	1 	2 	3 	2 	3 	4 	4


Mike Brookes
Semi retired gentleman from Copperfield College

On 21/04/2011 1:35 PM, Mark KELLY wrote:
>
> Would someone be kind enough to throw me a bone about the stack 
> question - Q3?
>
> I thought I knew stack implementation from my assembly language days 
> with Z80... this question feels like walking into someone's 
> half-finished thought process.  I'm really confused about this.After 
> half an hour of conjecture, I’ve tried four times to ask a series of 
> sensible questions to make sense of it, and have failed every time.
>
>
> The only apparent answer involves time travel, reversed arrays, 
> irrelevant stack pointers and bogus bolding of stack items.  The 
> relationship between the stack and the table is only the beginning of 
> the problem...
>
>
> I’d be delighted if anyone could walk me through this...
>
>
> Regards
>
> Mark
>
>

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