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Thread: 2013 HSC Paper Question 20 (SDD)

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    Question 2013 HSC Paper Question 20 (SDD)

    Been trying to figure out what I'm doing wrong with this question. (Q.20, SDD HSC 2013 Paper)

    I am completely stumped to how this question's correct answer is D.

    Anyone got have an explanation...

    Link to question here...

    Link to answers here...


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    Re: 2013 HSC Paper Question 20 (SDD)

    Quote Originally Posted by sparcut View Post
    Been trying to figure out what I'm doing wrong with this question. (Q.20, SDD HSC 2013 Paper)

    I am completely stumped to how this question's correct answer is D.

    Anyone got have an explanation...

    Link to question here...

    Link to answers here...

    It is C from the MG.

    LOAD b
    SUBTR a
    JMPN else

    IF b-a <0 then go to else statement. that is if b<a.
    This means the IF statement in the high level code corresponds with the else block in the CPU code.

    (Think of the ELSE case in the high-level language as the default, and so the default in the CPU code, is the JMPN code doesn't trigger a jump to "else")

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    Re: 2013 HSC Paper Question 20 (SDD)

    Oh yea I did this paper in class when we had finished the course early. I got it wrong at first I remember.
    So D loads 'a' into the accumulator. Because 'b' needs to be less than 'a', a - b needs to be positive. JUPN jumps if a - b is negative to 'else'. If a - b isn't negative then it just continues on.
    Actually... now I'm confused... lol
    Nvm, it's not D. I agree with C now but it's confusing because 'c=a' is under 'else' instead of c=b and the command for 'IF a>b', would be 'IF b>=a' in this case...
    IF b>=a THEN
    c=b
    ELSE
    c=a
    ENDIF
    which is the same as saying:
    IF a>b THEN
    c=a
    ELSE
    b=a
    ENDIF
    Correct me if I'm wrong because I'm actually a bit confused and might have overthought it.
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    Re: 2013 HSC Paper Question 20 (SDD)

    Quote Originally Posted by silverdawn565 View Post
    Oh yea I did this paper in class when we had finished the course early. I got it wrong at first I remember.
    So D loads 'a' into the accumulator. Because 'b' needs to be less than 'a', a - b needs to be positive. JUPN jumps if a - b is negative to 'else'. If a - b isn't negative then it just continues on.
    Actually... now I'm confused... lol
    Nvm, it's not D. I agree with C now but it's confusing because 'c=a' is under 'else' instead of c=b and the command for 'IF a>b', would be 'IF b>=a' in this case...
    IF b>=a THEN
    c=b
    ELSE
    c=a
    ENDIF
    which is the same as saying:
    IF a>b THEN
    c=a
    ELSE
    b=a
    ENDIF
    Correct me if I'm wrong because I'm actually a bit confused and might have overthought it.
    I really hope I don't take this long to solve a MCQ today in the exam though... I actually ended up deskchecking (not exactly, I drew a tree diagram for D & C...)
    Last edited by silverdawn565; 31 Oct 2017 at 8:56 AM. Reason: typo
    sparcut likes this.
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    Re: 2013 HSC Paper Question 20 (SDD)

    Interesting, I agree with C since:

    b is put into ACC then you subtract a from the ACC.

    If that results in a negative (aka a being greater than b), it puts a into ACC then stores that in c.

    Then visa versa; if the result is not negative, it will put the value of b into ACC then stores that in c.

    ...

    Are the answers wrong..?
    Last edited by sparcut; 31 Oct 2017 at 10:47 AM. Reason: typo

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    Re: 2013 HSC Paper Question 20 (SDD)

    Quote Originally Posted by sparcut View Post

    Are the answers wrong..?
    Lol. Pretty much what I thought for a second this morning. But C seems right its just weird that it seems reversed or something. Trick question?
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    Re: 2013 HSC Paper Question 20 (SDD)

    Quote Originally Posted by silverdawn565 View Post
    I really hope I don't take this long to solve a MCQ today in the exam though... I actually ended up deskchecking (not exactly, I drew a tree diagram for D & C...)
    I didn't do SDD, so I just did it knowing using intuition.

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    Re: 2013 HSC Paper Question 20 (SDD)

    Quote Originally Posted by dan964 View Post
    I didn't do SDD, so I just did it knowing using intuition.
    Oh. Well, intuition and common sense can get people far in life.
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    Re: 2013 HSC Paper Question 20 (SDD)

    Well... it was pointed out to me before the exam that the marking guidelines actually says C.

    I must have had some temporary dyslexia, cause I swear it said D.

    dan, you did say it was C from the marking guidelines, but I think I skipped over that, somehow didn't understand your acronym 'MG'.

    Cheers for the help anyway!

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