OCR A Level Computing - F453 - 23 June 2015

username1538497

2

Anyone else here taking this exam?

How's the revision going?

Reply 1

Amy99

8

What's A Level Computing like? I'm thinking of taking it

Reply 2

username1538497

OP

2

The specification for the exams I am taking is over and I don't know what the new specification will be like. However in AS, I had 2 exams, the first one is basically how a computer works (processors, memory managements, networks... ), the second exam is programming techniques which requires you to know how to program, write algorithms and basically all stuff about programming (testing method, for example). A2 we have 1 coursework, where we have to make a fully functional program for a client with documentation of every step. We also have an exam where we go into a lot of detail about how the computer actually works (so how does it do memory management and why does it process it like it does?)
All exams requires you to know the keywords, if you don't you will find understanding and passing the exam pretty hard. Overall, I think the programming exam is probably the hardest exam out of the 3.

Reply 3

Falldawn

anyone have any revision materials and want to share? :3

Reply 4

ms8061

5

Original post by Falldawn

anyone have any revision materials and want to share? :3

my teacher's got a pdf for each unit on our intranet, I'll see if I can rehost them somewhere (hope he doesnt mind)

in the meantime he's got a playlist with a bunch of videos of him going through parts of f453

(edited 8 years ago)

Reply 5

ms8061

5

Original post by Falldawn

anyone have any revision materials and want to share? :3

ok here's most of them, the one for 3.3.5 is too big to upload here so i'll find somewhere else

3.3.1 The function of operating systems 1213.pdf793.3KB

3.3.2 The function and purpose of translators 1213.pdf725.0KB

3.3.3 Computer Architecture 1112.pdf928.2KB

3.3.4 Data representation.pdf544.1KB

3.3.9 Databases.pdf752.0KB

3.3.6 High-level language programming paradigms.pdf575.2KB

3.3.7 Programming techniques.pdf881.6KB

3.3.8 Low level languages 2012-13.pdf807.5KB

Reply 6

Falldawn

Original post by ms8061

ok here's most of them, the one for 3.3.5 is too big to upload here so i'll find somewhere else

you are my hero :biggrin:

thanks!

Reply 7

pat6089

1

Are we expected to be able to write short algorithms following SQL Syntax? I haven't touched SQL yet. Its easy to understand as its close to english, but I don't know the syntax for writing it.

Reply 8

pat6089

1

Original post by Amy99

What's A Level Computing like? I'm thinking of taking it

The course is being scrapped right now and re designed to the a level "Computer Science". It will be based more off programming and designing solutions to problems, and less computing theory. Which some like, some hate. If you are interested in programming and problem solving, the course should be fine for you. I dislike it after 2 years myself. Right now, only 1 exam on programming and the rest is just mindless revision, *memory management, translators) which isn't being applied to anything in questions.

I wish I picked something else, but its a good qualification to have in this day and age.

Reply 9

username1538497

OP

2

Original post by pat6089

Are we expected to be able to write short algorithms following SQL Syntax? I haven't touched SQL yet. Its easy to understand as its close to english, but I don't know the syntax for writing it.

Yes, it's on the spec and I've seen a past paper question for it

Reply 10

Jmw123

3

Anyone have the June 2014 markscheme?

Reply 11

Nick_888

4

Hey I'm stuck on question 4a in the Jan 2011 paper:

A real binary number may be represented in floatingpoint binary notation using 5 bits for the mantissaand 3 bits for the exponent, both in two’s complementbinary.
(a) Three numbers P, Q and R are written in the formatdescribed but are not normalised.
P = 00100 010
Q = 00010 011
R = 00001 100
By converting each of P, Q and R to denary, showwhich represents a different value.SHOW ALL WORKING. [4 marks]

This is what the mark scheme says:
P: mantissa 0.010, exponent 010 = 2, P has binary value 1, denary value 1
Q: mantissa 0.001, exponent 011 = 3, Q has binary value 1, denary value 1
R: mantissa 0.0001, exponent 100 = -4, R has binary value 0.00000001, denary value 1/256
R represents a different value [dependent]

For P, why does the mark scheme say that the mantissa is 0.010 even though the question says it's 00100. What happened to the last 0?
And then for Q, the mark scheme says that the mantissa is 0.001 even though the question says it's 00010. What happened to the last 0 this time?

Please help. I get confused when binary numbers aren't normalised :/

Reply 12

ms8061

5

Original post by Nick_888

Hey I'm stuck on question 4a in the Jan 2011 paper:

A real binary number may be represented in floatingpoint binary notation using 5 bits for the mantissaand 3 bits for the exponent, both in two’s complementbinary.
(a) Three numbers P, Q and R are written in the formatdescribed but are not normalised.
P = 00100 010
Q = 00010 011
R = 00001 100
By converting each of P, Q and R to denary, showwhich represents a different value.SHOW ALL WORKING. [4 marks]

This is what the mark scheme says:
P: mantissa 0.010, exponent 010 = 2, P has binary value 1, denary value 1
Q: mantissa 0.001, exponent 011 = 3, Q has binary value 1, denary value 1
R: mantissa 0.0001, exponent 100 = -4, R has binary value 0.00000001, denary value 1/256
R represents a different value [dependent]

For P, why does the mark scheme say that the mantissa is 0.010 even though the question says it's 00100. What happened to the last 0?
And then for Q, the mark scheme says that the mantissa is 0.001 even though the question says it's 00010. What happened to the last 0 this time?

Please help. I get confused when binary numbers aren't normalised :/

at a guess its because you can look at them in the same way you'd look at trailing zeroes when dealing with decimal numbers
e,g 0.0230000 could be written as 0.023 and make sense still

Reply 13

pat6089

1

Hi guys. Anyone care to give me a hand understanding the use of a virtual machine? I always thought of it as a way of being able to access programs which wouldn't be accessible due to different machine code (Like running Windows on a Mac), but apparently its just a the act of finishing the translation from intermediate code to machine code? Am I wrong? I thought i was completely clear on that understanding until now.

Reply 14

ms8061

5

Original post by pat6089

Hi guys. Anyone care to give me a hand understanding the use of a virtual machine? I always thought of it as a way of being able to access programs which wouldn't be accessible due to different machine code (Like running Windows on a Mac), but apparently its just a the act of finishing the translation from intermediate code to machine code? Am I wrong? I thought i was completely clear on that understanding until now.

My understanding of a virtual machine is that it's basically an OS within an OS. It has most of the features of an OS (hence how its used to run windows on a mac), and interprets the intermediate code as if it was running on a physical system.

its a bit wishy-washy, and they came up last year so fingers crossed they won't appear again.

(edited 8 years ago)

Reply 15

Falldawn

Original post by pat6089

Hi guys. Anyone care to give me a hand understanding the use of a virtual machine? I always thought of it as a way of being able to access programs which wouldn't be accessible due to different machine code (Like running Windows on a Mac), but apparently its just a the act of finishing the translation from intermediate code to machine code? Am I wrong? I thought i was completely clear on that understanding until now.

All i know about VM is that it is a piece of software that is required to run intermediate code

Reply 16

username1538497

OP

2

A virtual machine is a software which allows you to run an OS or immediate code. As each computer is different it is hard to program for them all, so they are build using interpreters, which runs the software on VM. Imagine running mircosoft word on mac, it would be running through a vm (even though it does look like it).

Here's a virtual machine that can run an OS: https://www.virtualbox.org/

Software/program which runs on VM, works just like normally would.

(edited 8 years ago)

Reply 17

Nick_888

4

If they asked you to describe a quick sort method, what would you talk about?

Reply 18

username1538497

OP

2

Original post by Nick_888

If they asked you to describe a quick sort method, what would you talk about?

- Random pivot point chosen
- Bigger on right, small on left
- Repeated
- Problem is divided each time pivot point chosen
- Then sorted in order traversal method
- Fast on big list, slow on small lists

(edited 8 years ago)

Reply 19

mindlessstudent

answer to question 4???

OCR A Level Computing - F453 - 23 June 2015

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