Hey everyone,

I was just wondering if anyone has a nice, concise summary of all the calculation-based questions that could be asked in the HSC exam

And also, I still don't understand how parity bit checking works so if someone could explain it, that would be wonderful!

Good luck to everyone for Wednesday!!

Get your cameras everybody. Somebody actually posted in this thread... Alright, I'll be serious.

This thread has a list of all the multimedia cauclations:

http://community.boredofstudies.org/29/information-processes-technology/154889/multimedia-formulas-thread.html Keep in mind that you are not allowed to bring a calculator into the exam, so they can't make the calculations too difficult.

As for parity checking: imagine you want to send the following to another computer:

When the computers are handshaking, they decide what type of parity to use. If it is even parity, then you want there to be an even number of 1's in the data. If it is odd, then you want there to be an odd number of 1's. They achieve this by adding an extra bit (called the parity bit) at the end of the message. Let's say that they are using even parity to send the above message. There are five 1's in the message, so the parity bit added will be a 1 in order to make an even number of 1's:

If they decided on odd parity, then they would add a zero in order to keep the odd number of 1's:

Let's say that the transmission was corrupted, and the second bit was changed from a zero to one (while using the even parity one). It would look like this:

There are an odd number of 1's there, so the receiver knows that an error has occurred, as there is meant to be an even number of 1's. However, what if two bits were corrupted? For example, what if the second and third bits were changed from zeros to ones:

This is an even number of 1's, so the receiver can't tell that an error has occurred. Thus, there is about a 50% failure rate for parity bits. So, while it is better than nothing, it still isn't very good.

I hope this helps. Good luck for the exam.