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# Computing AQA CPT4- MODULE 4 watch

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1. how did you find it?

did u get -1.25 for the decimal number on that floating point question?
2. bump
3. There was a floating point question?
4. floating point wtf? i just remember it saying take 6 from 18 or something and SHOW how the steps are done
5. It said what was the hex number A802 in binary, and decimal, when stored using floating point (12 bit mantissa, 4 bit exponant)

-1.25 anyone?
6. (Original post by friday13th)
It said what was the hex number A802 in binary, and decimal, when stored using floating point (12 bit mantissa, 4 bit exponant)

-1.25 anyone?
ah right, i just converted the hex number into binary then binary into decimal, cant remember what i got tho
7. (Original post by friday13th)
It said what was the hex number A802 in binary, and decimal, when stored using floating point (12 bit mantissa, 4 bit exponant)

-1.25 anyone?
Did it say in floating point???
Oops!
8. Hang on, i don't think it was floating point.
There was no room to work out the answer, and it wasn't worth enough points for a floating point Q, i thought.
9. It said it had a 12 bit mantissa, and a 4 bit exponant!!!

So it has to be floating point

listen

A802 = hex
1010100000000010 = binary

[1] [01010000000] [0010]

[1] = sign bit= negative so the number is - something
[0010] = exponant = 2 in decimal, which means u move the decimal point 2 places

so take the mantissa and move the decimal point two places

1.010000.... is what you get

in decimal this is

1.25

please tell me i am right

yes the question was only four marks
10. yeah it was floating point, was 4 marks (one for convering to binary, three for converting that binary number into decimal using twos complement) i got -2.75, i think the number was 1010100000000010
11. (Original post by friday13th)
It said it had a 12 bit mantissa, and a 4 bit exponant!!!

So it has to be floating point

listen

A802 = hex
1010100000000010 = binary

[1] [01010000000] [0010]

[1] = sign bit= negative so the number is - something
[0010] = exponant = 2 in decimal, which means u move the decimal point 2 places

so take the mantissa and move the decimal point two places

1.010000.... is what you get

in decimal this is

1.25

please tell me i am right

yes the question was only four marks
i thought it was 101.01 after moving two places to the right
12. Oh, you dont include the sine bit in the moving the decimal point...s-man
13. how about showing 6 take away from 18?

first i said its the same as 18 + ( - 6 )
u can either make the most significant bit NEGATIVE or get the binary for the number 6, then INVERT THE BITS and then add one

then i added 18 to 6 ( minus 6 ) which gave correct answer ( in binary ) and u can check the answer in binary with 18 - 6
14. (Original post by Iluvatar)
I thought you had to do both?
as long as u include the method and calculate the correct answer its all good
i just mentioned u had to invert, add 1, make the msp a minus and then calculate, carrying the 1's when there were a double one etc
15. You are right friday13th it was -1.25, dunno what every1 else is on about
16. thank you god

thats the only page i got marks on lol
17. ya, I cocked the conversion of the -1.25 bit up.

The 18-6 was pretty straightforward... convert +6 into -6, then add it.

So 18 + (-6).

Came out with 12 in binary... I think that was right :P
18. (Original post by KiLLeRSpaM)
ya, I cocked the conversion of the -1.25 bit up.

The 18-6 was pretty straightforward... convert +6 into -6, then add it.

So 18 + (-6).

Came out with 12 in binary... I think that was right :P
ye thats right any1 get wat the algorithm does?
19. for the floating point q:

mantissa=101010000000= [-(2^11)+(2^9)+(2^7)] / (2^11) = (-11/16)

exponent= 0010= 2^2 = 4

answer = (-11/16) * 4 = -2.75

the method also matches all the floating point questions given in past papers
20. (Original post by jay9386)
ye thats right any1 get wat the algorithm does?
binary search is what i put

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