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AQA A2 COMP 3 Computing 2015 - Official Thread

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Original post by ToxicFlop
What were the two reasons for using a digital certificate? I could only think of can prove that a message is genuine?


I think the other is to prove it definitely came from the person that sent it so if A sent it, the digital certificate can tell you whether it did come from A or not

(The other being that it is definitely the original message and that it hasn't been tampered with or changed)

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(edited 8 years ago)
Original post by ToxicFlop
What were the two reasons for using a digital certificate? I could only think of can prove that a message is genuine?


Yeah, I never learnt any reason other this. I just said to ensure that the message didn't get corrupted during transmission.
Well, there's a good chance I haven't failed.
Really handy when the exact topic you revised the night before comes up :wink: It seemed fairly easy, will hopefully only drop the odd mark here and there.
Original post by StarvingAutist
Well, there's a good chance I haven't failed.


Very jealous :frown:

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Did anyone have a table with a 4 attribute composite key?
Original post by Iridann
Did anyone have a table with a 4 attribute composite key?


I used 3 I think. I wasn't sure about the fourth though.


Original post by AnnieFraz


I could be wrong :lol:
Original post by Iridann
Did anyone have a table with a 4 attribute composite key?


I had three, but not four.
Original post by StarvingAutist
I used 3 I think. I wasn't sure about the fourth though.




I could be wrong :lol:


Original post by EXTREMEninja
I had three, but not four.


Yeah I wasn't sure either tbf.

Mine had Candidate,Centre,ModuleCode,ExamSession

Think I did my weird tbf.
Original post by Iridann
Yeah I wasn't sure either tbf.

Mine had Candidate,Centre,ModuleCode,ExamSession

Think I did my weird tbf.


I used CandidateNumber, CentreNumber and ExamSession as my primary key.
Original post by Iridann
Yeah I wasn't sure either tbf.

Mine had Candidate,Centre,ModuleCode,ExamSession

Think I did my weird tbf.


I don't know if mine is right or not. Hopefully we should both get some marks for some tables, even we get the rest wrong XD
Original post by ToxicFlop
What were the two reasons for using a digital certificate? I could only think of can prove that a message is genuine?


To check for integrity (data hasn't been corrupted or modified in transit) and authenticity (the sender is who they say they are).
The paper was nice. I suspect I may lose marks on the first SQL question this time, as the mark schemes have typically been quite stringent as to what they accept for similar questions in the past. Other than that, it was a nice paper. The 7-mark question was lovely.

Either way, that's all my exams finished!
(edited 8 years ago)
Original post by Exaltation
Why are you assuming there aren't any C grade students on TSR? :tongue:


I've been reading this thread and everyone here seems pretty smart! :P
I can add the C grades if anyone would like me to! LOL
So, though i'd join in on the discussion... Everyone seems to have found the trace table hard but I thought the trace table was pretty good, just required alot of time to trace it out but you have 2 hours 30 anyway! :biggrin:
So, question time -

Firstly, for the two reasons for digital certificate, i said to check it was from the original person and that it hadn't been tampered with which is what everyone else is saying but would the mark scheme be harsh and say the words "integrity" and "authenticity" must be used as I didn't use those words but explained the same thing

Secondly, for the hashing question (the one with the database, not the digests) i'd never learnt about it due to it not being in the book and I didn't know it even existed until that morning, I got 751 for both which I'm happy with but what was the correct answer for stopping a collision? I just said some BS about multiplying it by 10 to find a number not already allocated...
Original post by Matt_Stark
So, though i'd join in on the discussion... Everyone seems to have found the trace table hard but I thought the trace table was pretty good, just required alot of time to trace it out but you have 2 hours 30 anyway! :biggrin:
So, question time -

Firstly, for the two reasons for digital certificate, i said to check it was from the original person and that it hadn't been tampered with which is what everyone else is saying but would the mark scheme be harsh and say the words "integrity" and "authenticity" must be used as I didn't use those words but explained the same thing

Secondly, for the hashing question (the one with the database, not the digests) i'd never learnt about it due to it not being in the book and I didn't know it even existed until that morning, I got 751 for both which I'm happy with but what was the correct answer for stopping a collision? I just said some BS about multiplying it by 10 to find a number not already allocated...


I put that you could either use Closed Hashing - Which would put the data into the next available location, or Open Hashing - Where it would start a linked list within the same array position using pointers to point to where in the memory the other data is (so it would be in the same hashed number position as any other data with the same hash value but in a different memory location)

(If that made any sense :smile: )
Original post by sophuscus
I put that you could either use Closed Hashing - Which would put the data into the next available location, or Open Hashing - Where it would start a linked list within the same array position using pointers to point to where in the memory the other data is (so it would be in the same hashed number position as any other data with the same hash value but in a different memory location)

(If that made any sense :smile: )


Ah that makes sense, i'll keep that in mind for my uni course :biggrin:
(i'm really quite annoyed how terrible the AQA endorsed text book actually is though, thought i could rely on that but I guess not :biggrin: )
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Jurge
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For the question where it asked what kind of error the calculation produced, what kind of error was it?
Does anyone know when the comp4 projects finish getting moderated by aqa?


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Original post by Comp.Girl
Does anyone know when the comp4 projects finish getting moderated by aqa?


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I don't think there is any real time, I think we just get told the moderated grade in August with the COMP3 grade (at least that is what's happening with my sixth form)
Original post by Matt_Stark
I don't think there is any real time, I think we just get told the moderated grade in August with the COMP3 grade (at least that is what's happening with my sixth form)



We were supposed to get our project marks this week but my college have decided to change their policy so you only receive your marks/grade after aqa have moderated it.. -.-


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