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# COMP3 - JUN 2016 Discussion Thread watch

1. How quickly do most of you finish? I reckon I'll have an hour to stare at questions I don't know how to answer
Is it just me or are grade boundaries really high for this paper, considering that they aren't particularly easy and that the markschemes aren't very forgiving either? :L
Yes, not many people aim for more than an A in this exam so it's surprising that the boundaries are so high. Comparing to OCR Physics where you need around 70/100 for an A*

(Original post by TheKian)
How quickly do most of you finish? I reckon I'll have an hour to stare at questions I don't know how to answer
Yep, I think everyone will finish early. No idea why the exam is 2.5 hrs when there is really only about 1.5 hrs worth of questions. You'll either be able to answer them or you won't, it's not like Maths where more time will let you think the problem through more and correct mistakes
3. (Original post by QuantumSylar)
The grade boundaries for this are so ****ed lol.
Is anyone else in my position?
I need 58 on comp 3 for B grade
86 for A*
Yeah man, after my AS results I need to average 65% this year for an A, which is what I need for uni... Shouldn't be too hard in theory but a lot of my exams so far have stepped up a bit difficulty-wise, so praying the same won't be true for COMP3 D:
4. I NEVER got this.

How can you figure out the largest/smallest positive and negative number for a number with a specific amount of bits??
5. (Original post by Yendis)
I NEVER got this.

How can you figure out the largest/smallest positive and negative number for a number with a specific amount of bits??
You could memorise them or figure it out in the exam (probably can't remember them now...)

Largest Positive
First of all know that the mantissa must be positive (so the first bit in the mantissa is a 0). The mantissa may as well then be as big as you can possibly get it to be as it will all add up in the end, so the rest will be 1's

You will also want the exponent to be as big as possible (not negative!) so the first bit will be 0 followed by all 1's

Lowest Negative
The mantissa will be negative as the number you are looking for is negative, so the first bit is a 1

Any subsequent 1's in the mantissa will actually make the mantissa smaller (as -1 + 1/2 = -1/2...) so you will want the rest of the mantissa set to 0's

Smallest positive (non zero)
You want mantissa to be positive, so the first bit is a 0

You'll want the mantissa to be as small as possible (but still positive) so the rest should be 0's except the last bit in the mantissa as that will create the smallest positive mantissa you can get

The exponent will only make it bigger unless it is negative, so set the first bit to 1 and then the rest will be 0 because any 1's following it will actually make the exponent higher (and therefore you'll get a higher number)

Smallest Negative (closest to 0 but not 0)
What do you think?
6. (Original post by bartbarrow)
You could memorise them or figure it out in the exam (probably can't remember them now...)

Largest Positive
First of all know that the mantissa must be positive (so the first bit in the mantissa is a 0). The mantissa may as well then be as big as you can possibly get it to be as it will all add up in the end, so the rest will be 1's

You will also want the exponent to be as big as possible (not negative!) so the first bit will be 0 followed by all 1's

Lowest Negative
The mantissa will be negative as the number you are looking for is negative, so the first bit is a 1

Any subsequent 1's in the mantissa will actually make the mantissa smaller (as -1 + 1/2 = -1/2...) so you will want the rest of the mantissa set to 0's

Smallest positive (non zero)
You want mantissa to be positive, so the first bit is a 0

You'll want the mantissa to be as small as possible (but still positive) so the rest should be 0's except the last bit in the mantissa as that will create the smallest positive mantissa you can get

The exponent will only make it bigger unless it is negative, so set the first bit to 1 and then the rest will be 0 because any 1's following it will actually make the exponent higher (and therefore you'll get a higher number)

Smallest Negative (closest to 0 but not 0)
What do you think?
thank you for the clarification (y)
7. So seeing as simulation hasnt come up in a while really (in a big way atleast) what resources is everyone using for simulation? Anyone got any tips if a big marker q comes up? I can barely think of 4 points about simulation.
8. And on a side note has anyone done the specimen paper? wtf its hard
9. Just looking over last year's examiner's reports, there seems to be emphasis placed on:

Turing machines

I can see them asking us to design a database again (remember the 3 normal forms!)

Subnet masks (And them with the source and destination to get the Subnet ID of both)

Firewalls

hashing and binary search

Tracing an algorithm

SQL Queries

10. (Original post by dinodazer)
Yeah man, after my AS results I need to average 65% this year for an A, which is what I need for uni... Shouldn't be too hard in theory but a lot of my exams so far have stepped up a bit difficulty-wise, so praying the same won't be true for COMP3 D:
yh true some AQA papers this year have been so nasty, like the c3 maths paper
11. Don't suppose you have a copy of that?

(Original post by Ainsleyy)
And on a side note has anyone done the specimen paper? wtf its hard
12. Could somebody quickly make a quick summary of subnet masks and Subnet IDs? I'm pretty sure I get it, but I want to be certain, thanks.
13. How can you tell if a floating number is not normalised?
14. (Original post by TercioOfParma)
How can you tell if a floating number is not normalised?
15. (Original post by Polyrogue)
So no more than 1 zero at the start for the sign?
16. (Original post by TercioOfParma)
So no more than 1 zero at the start for the sign?
it means it starts with 0.1 or 1.0 ( and not 0.01 or 1.11110 or such)
17. (Original post by Polyrogue)
Could somebody quickly make a quick summary of subnet masks and Subnet IDs? I'm pretty sure I get it, but I want to be certain, thanks.
Subnet mask identifies which computers are on the same segment
Subnet mask does an AND operation with the student's computer IP address
Result of AND operation is the network ID
Network IDs compared
If the networks id dont match computers arent on same segment

network id/ subnet id i think theyre the same and this was worth 6 points
18. (Original post by QuantumSylar)
Subnet mask identifies which computers are on the same segment
Subnet mask does an AND operation with the student's computer IP address
Result of AND operation is the network ID
Network IDs compared
If the networks id dont match computers arent on same segment

network id/ subnet id i think theyre the same and this was worth 6 points
Just in time, and as suspected. Thanks a lot!
19. So how did everyone find it?

For the table of 3 notations i said the 2nd one is a flowchart what did you guys say it was
20. There was a question about the how to make the floating point more precise without losing the range. I since the pattern is always 1.0 or 0.1 we can represent the 2 patterns using one bit where a 1 = 0.1 and a 0= 1.0 this way you can free up a bit space in the mantissa without using any bits from the exponent. (3 or 4 marks)

The Question about picking a number to show what things are similar to the Turing machine I wrote 4,3.(2 marks)

The transition function question did everyone end up on state Sr with the following data in the tape at the end ###01. (6 marks)

For the question asking what it does i said it rearranges the data in the tape backwards. (1 mark)

for the delete algorithm i wrote:
current <== Start
While Current.Datavalue not equal to DelItem
do
Previous <== current
Current <== Current.Next
End of While
Previous.Next <== Current.Next
Release (Current)
(8 marks)

for the regex question I got (a ((ba)*c*a)|bb|bc)) |b|c) (a|b|c)* (1 mark)

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