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# CPT 1 and 2 watch

1. (Original post by Xulfer)
Important: Parity bit goes at the front (left hand side) if it says "MSB" or Most Significant Bit, and at the end (the right hand side) if it says Least Significant bit. That's because the number on the right could only change the number by 1 if it was wrong, on the left it could change it by hundreds if the data is corrupt (depending on the size of the binary number)

010110101
^ ^
MSB LSB

-=X=-
oh yeah, forgot about checking for MSB/LSB
2. I tried to point to the LSB but the post wouldnt allow the space in the text that I used, so my little text diagram there is wrong I edited it now though.

Remember, read the question I can tell you're clever, so it's easy to lose marks that way by thinking "this is easy" and not reading the whole of the question

-=X=-
3. (Original post by Xulfer)
I tried to point to the LSB but the post wouldnt allow the space in the text that I used, so my little text diagram there is wrong I edited it now though.

Remember, read the question I can tell you're clever, so it's easy to lose marks that way by thinking "this is easy" and not reading the whole of the question

-=X=-
hehe, nice editing....yeah you do have to be careful, but i'm usually quite good at that in exams about reading the questions properly...especially in computing, becasue there's normally a lot of time left
4. Yes, i usually finish in half an hour, and then sit their eviling the examiners

I did CPT1 in january, CPT2 today, any last minute information which is mandatory?
5. Yep, just remember that it's REALLY quick to finish this exam, (CPT3 half of us finished in 30 and went to sleep for an hour...literally...my mate had marks all over his face from his arm ) So you really do have enough time to read the question properly and think it over before you write something down quickly. I hate checking over exams at the end, especially after a 3 hours history essay or something, you just can't be arsed and it doesn't seem worth it for a mark or 2 Plus I don't wanna think "oh crap that's wrong....oh crap that's wrong too" and not have enough time to change it all.

-=X=-
6. (Original post by Xulfer)
Important: Parity bit goes at the front (left hand side) if it says "MSB" or Most Significant Bit, and at the end (the right hand side) if it says Least Significant bit. That's because the number on the right could only change the number by 1 if it was wrong, on the left it could change it by hundreds if the data is corrupt (depending on the size of the binary number)

010110101 < LSB
^
MSB

-=X=-
why can you only change the number by one on the right hand side? anyways the example above there are only 40s but 51s, so thats an error right
7. Sorry, I just hit a load of numbers.

The ASCII characters are made up of 7 bits, and the final 8th bit is the parity check. Let's say the number is 4, ignoring the ASCII 7 bit crap for a minute:

00000100 = 4 right?

Well if you're doing LSB even parity then it's:

00001001

If it's MSB then it's

10000100

-=X=-
8. Completely unrelated problem:

The exam board seem to hate you using new technology. It sometimes says "Which medium would be suitable for storing 7gb or data blah blah"

They want you to say HDD - in the AQA specific text book it says "Hard disks typically have a capacity of between 2gb and 10gb" which is completely out of date, and for 7Gigs, it'd be a complete waste of a 160+gb HDD.

Also the problem comes in the form that they say "medium" instead of "media". They've done this on all the past papers, and medium means for example a drive, and media would be a CD. However, when they say medium they mean the storage media not the device used to store it.

One way to get around this is to write "USB flash drive" because that's both media and medium But they don't even like you saying DVD so I doubt you'd get away with that

Stupid AQA. The question is gonna come up on CPT2. I'll just write DVD-R.

-=X=-
9. okay everyone, i'm off to school. good luck, and i'll be back on here tonight to discuss
10. Good luck

-=X=-
11. would DVD-R be right?
12. I'm guessing it would be, because it's WORM - Write Once Read Many. I think. I'd be relucant to write hard drive because of the size of them these days. DVD-R would be more suitable than DVD. Maybe DVD-RW? I dunno...

-=X=-
13. true, i see what you mean about them picking sizes that cause confusion, DVD-R i think.
14. in the book it says: when data is transmitted, the parity bits are checked at both the sending and receiving end, if they are different,an error message is displayed -

so the start and stop bit are both either 0 or 1?
15. .
16. Stop and stop bits are different from parity bits. For that you'd have the parity bit at either end (depending on it being LSB or MSB) then you'd have the start and stop bits at both ends Nice and confusing.

What they mean by checking, is that before it's sent it is checked, then once the data is received it is checked there. The start and stop bits are so that it know where to - yes you guessed it - start and stop.

-=X=-
17. (Original post by TheWolf)
in the book it says: when data is transmitted, the parity bits are checked at both the sending and receiving end, if they are different,an error message is displayed -

so the start and stop bit are both either 0 or 1?
Yes.

Back to the 7GB thing, i've thought about it, i reckon you'd get full marks if you put hard-disk, however, it depends what it's for, like, a police checker, hard-disk, but something which has to be moved, blah, i cant think of a good AQA example.
18. (Original post by Xulfer)
Stop and stop bits are different from parity bits. For that you'd have the parity bit at either end (depending on it being LSB or MSB) then you'd have the start and stop bits at both ends Nice and confusing.

What they mean by checking, is that before it's sent it is checked, then once the data is received it is checked there. The start and stop bits are so that it know where to - yes you guessed it - start and stop.

-=X=-
oops yeah, sorry I didn't read what you said properly ^ I didn't mean to patronise you I just thought you didn't know what the stop and start bits are used for Yes they'd both be either 1 or 0. Although I don't know why and I've already done that module...I should be revising CPT2

-=X=-
19. Hmm, i haven't revised one bit, i think ill be 'alright'

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