AQA AS Computing - COMP2 - June 3rd 2015 - Exam Discussion Thread

Let's start this schnitzel off with getting people's prediction for questions:

Anyone got any idea of the Hardware this year?

I can't get my head around simplifying boolean expressions, is there an easy way to do it? They have come up in the last two papers so AQA love them

What do you mean?



People who have done Electronics A-Level will find this so easy. One thing you can do is say the equation to yourself.
For example:
B . (A + A^)
Would be:
(A OR NOT A) AND B
And when you see that you should logically think, A OR NOT A is always true. So you are left with B AND TRUE. Then if you think logically about that the answer will just be B. Not sure if that made any sense to you, but it is a good way to do it.

-----

There are also a load of small rules you can remember:
A . A^ = 0
A + A^ = 1
A . 0 = 0
A . 1 = A
A + 0 = A
A + 1 = 1

So for the equation you used above you could replace the A + A^ with 1, leaving you with:
B . 1, but then you can replace that with just B using those rules.

----

Also remember De Morgans theorem. Make a bar and change the sign, or break the bar and change the sign. That's a simple way to remember it.

-----

Hopefully that made sense, if not just ask. Keep practicing and you will get it eventually.

Can someone explain to me the pros and cons of interpreters and compilers? Thanks!

No offence, but did you even bother to look for an answer yourself. The answer can be found in a textbook or on the internet pretty quickly, and it's not complicated.

Pro's of using a compiler for a program:
- No need to distribute the source code (and the user wont need a compiler)
- Program runs faster than an interpreted one

Pro's of using an interpreter for a program:
- Program can be executed immediately (no waiting for it to compile)
- Helpful for finding errors when building the program, instead of the program crashing

Thanks. I had looked at wikibooks first and also do not prefer the book.

I can't get my head around simplifying boolean expressions, is there an easy way to do it? They have come up in the last two papers so AQA love them

I take a very math-y approach to it.

E.g. B.A^ + B.A, You see a "common factor" B so take out B leaving (A^ + A) whereby one can easily guess that if a is 0, then 1 OR 0 gives 1 and if A is 1, 0 OR 1 gives 1 hence B.1 = B
(Obviously that's one of many examples, like expanding a factorised polynomial)

I'd probably do similar for that question.

And if you get confused, you can always draw a truth table for the question and your answer to compare the results.

ALERT:

They will ask like a 1 marker on logic errors. Why? (I'm not even sure if it's called a logic error, don't judge).
The following: