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AQA A Level Computer Science Paper 2 June 22nd 2017 watch

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    Official thread for paper 2 computer science. Looking forward to killing this paper after that crash and burn in paper 1.

    Hoping this paper will be relatively easy and bring y grade up to a C/B as I got like 30 marks in that paper 1 exam. How are u guys feeling about paper 2?
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    Think they're definitely gonna **** us over again
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    (Original post by 105)
    Official thread for paper 2 computer science. Looking forward to killing this paper after that crash and burn in paper 1.

    Hoping this paper will be relatively easy and bring y grade up to a C/B as I got like 30 marks in that paper 1 exam. How are u guys feeling about paper 2?
    Thank God I'm not alone. I thought I was the only one who got a grade from the opposite side of the alphabet in Paper 1
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    Do you guys know of any end of chapter tests for Paper 2? I can't find any
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    There's a playlist here that covers almost all of the paper 2 topics if anyone needs help with revision.

    https://www.youtube.com/playlist?lis...XYufpZo3pJgotk
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    (Original post by Joseph....)
    Do you guys know of any end of chapter tests for Paper 2? I can't find any
    These can be found on 'exampro'

    its £80 but usually the school buys it so ask your computer science teacher.
    They have every question that ever came up on AQA paper 2 and are really helpful as AQA loves to repeat similiar questions
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    Does questions from the additional questions come up in the real exam? Or are they just there for practise


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    (Original post by yungabzzz)
    Think they're definitely gonna **** us over again
    i doubt it, considering the specimen paper was relatively straight forward and we are the first year of the new spec, they shouldnt really f*** us over

    then again this is AQA...
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    Is anyone able to explain partial function application and its notation? I get the concept of functional programming but I've never really understood this part. In the spec it defines the notation we need to know with an example for a function which adds two integers:

    Using function application add: int x int --> int "where integer x integer is the Cartesian product of
    the set integer with itself."

    Using partial function application add: int --> int --> int

    I don't get how this makes any sense...
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    (Original post by Fastrack)
    Is anyone able to explain partial function application and its notation? I get the concept of functional programming but I've never really understood this part. In the spec it defines the notation we need to know with an example for a function which adds two integers:

    Using function application add: int x int --> int "where integer x integer is the Cartesian product of
    the set integer with itself."

    Using partial function application add: int --> int --> int

    I don't get how this makes any sense...
    Partial Application of a function is the process of applying a function by creating an intermediate function (temporary function) by fixing some of the arguments to the function.

    For example: add: int -> int -> int
    - This is an example of particle function application that shows a new function being created, which always adds the first argument onto a number. This new function is then applied to the second argument to produce the overall result.

    - So basically it creates a temporary function that adds whatever input on the second function onto a the function defined previously.

    E.g. Add (2, 3) = add2 (3) = 5
    - add2 is a temporary function created


    This differs from full application of a function, which for adding would take two integers as the argument and add them together to create an integer

    E.g. Add(2, 3) = 5

    Hope that helps
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    (Original post by jamesgrimshaw)
    There's a playlist here that covers almost all of the paper 2 topics if anyone needs help with revision.

    https://www.youtube.com/playlist?lis...XYufpZo3pJgotk

    Thank you!
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    (Original post by Nouie)
    Partial Application of a function is the process of applying a function by creating an intermediate function (temporary function) by fixing some of the arguments to the function.

    For example: add: int -> int -> int
    - This is an example of particle function application that shows a new function being created, which always adds the first argument onto a number. This new function is then applied to the second argument to produce the overall result.

    - So basically it creates a temporary function that adds whatever input on the second function onto a the function defined previously.

    E.g. Add (2, 3) = add2 (3) = 5
    - add2 is a temporary function created


    This differs from full application of a function, which for adding would take two integers as the argument and add them together to create an integer

    E.g. Add(2, 3) = 5

    Hope that helps
    Thank you!!! That really helps, but one thing I still don't really understand is the notation they're using for function application. How does Integer x Integer represent addition?
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    Can someone help me with these questions.

    What is a Wireless Access Point?

    What is a Wireless Network Adapter?

    How are wireless networks secured?

    What is a MAC Adress white list?
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    (Original post by 105)
    Can someone help me with these questions.

    What is a Wireless Access Point?

    What is a Wireless Network Adapter?

    How are wireless networks secured?

    What is a MAC Adress white list?
    Good questions, i usually get confused between them aswell


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    (Original post by Fastrack)
    Thank you!!! That really helps, but one thing I still don't really understand is the notation they're using for function application. How does Integer x Integer represent addition?
    I find the notation confusing and bizarre too, but in this case I think I understand it. As you quote, "integer x integer is the Cartesian product of the set integer with itself". So the Cartesian product of two sets is any tuple with one member of each set - e.g. {a, b, c} x {1, 2, 3} = {(a, 1), (a, 2), (a, 3), (b, 1), (b, 2), (b, 3), (c, 1), (c, 2), (c, 3)}.

    So integer x integer is something in the form (a, b) where a and b are both integers. "add: int x int --> int" means "add is a function such that when you supply the parameters (a, b) [both integers], it will return a value c [also an integer]". For example, add(3, 4) = 7.

    To give another example, I think we could definite division with integers as "divide: int x int --> rational", because the divide operation also takes two parameters, and if you do integer ÷ integer you will get a rational number (assuming the second integer is non-zero). [Or you could have "divide: real x real --> real" if you wanted to be able to divide any two real numbers.]
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    (Original post by 105)
    Can someone help me with these questions.

    What is a Wireless Access Point?
    A piece of hardware used to connect a device to a wireless network. Most modern day routers will contain a wireless access point, but a WAP can also be a separate device e.g. large offices may need several WAPs connecting to the same router to cover the whole area of the office.

    What is a Wireless Network Adapter?
    Basically what it sounds like. It allows a device to connect to a wireless network. As far as I can tell, devices like laptops have built in WNAs but if you wanted to (for example) connect a desktop PC to WiFi you would need a USB wireless network adapter.

    How are wireless networks secured?
    So first, the reason that wireless networks are less secure than wired networks is because they communicate by sending electromagnetic signals through the air, and these signals can be intercepted much more easily than a signal through a wire. The way they can be secured is with the following:
    • Use WPA/WPA2 (WiFi Protected Access), a protocol which uses a very secure method of encryption.
    • Disable broadcast of your SSID (the identifier for the network).
    • Use a MAC address whitelist (see below).

    What is a MAC Adress white list?
    A whitelist is the opposite of a blacklist - while a blacklist contains the things that are not allowed, a whitelist contains the things that are allowed. In this case, the things being listed are MAC addresses - numbers assigned to each physical device (hard-coded into its Network Interface Card). So you specify the devices you want to be able to connect to the network (e.g. your desktop, your laptop and your iPad) and only these devices will be allowed to connect to the network.
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    (Original post by ShatnersBassoon)
    I find the notation confusing and bizarre too, but in this case I think I understand it. As you quote, "integer x integer is the Cartesian product of the set integer with itself". So the Cartesian product of two sets is any tuple with one member of each set - e.g. {a, b, c} x {1, 2, 3} = {(a, 1), (a, 2), (a, 3), (b, 1), (b, 2), (b, 3), (c, 1), (c, 2), (c, 3)}.

    So integer x integer is something in the form (a, b) where a and b are both integers. "add: int x int --> int" means "add is a function such that when you supply the parameters (a, b) [both integers], it will return a value c [also an integer]". For example, add(3, 4) = 7.

    To give another example, I think we could definite division with integers as "divide: int x int --> rational", because the divide operation also takes two parameters, and if you do integer ÷ integer you will get a rational number (assuming the second integer is non-zero). [Or you could have "divide: real x real --> real" if you wanted to be able to divide any two real numbers.]
    Ahh, so in essence "integer x integer" is just saying that the function takes 2 arguments of type integer and we can use the notation for any function
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    I have a question:

    If eight bits are used to store one character, what is the bit pattern when the string ‘25’ is stored in a 16-bit word?

    I got 00000010 00000101

    but answer is 00110010 0011010

    Why ?
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    (Original post by sideshowbobya)
    I have a question:

    If eight bits are used to store one character, what is the bit pattern when the string ‘25’ is stored in a 16-bit word?

    I got 00000010 00000101

    but answer is 00110010 0011010

    Why ?
    It wants the ASCII code, not just the binary numbers (otherwise it would just be 000...0011001).

    The ASCII values for lowercase numbers start at 00110000 for '0', and then 00110001 is '1' etc. up to 00111001 for '9'. I've never seen an exam question that doesn't tell you the ASCII code for '0', so you should be able to work out the values from there. (A similar thing could happen if they gave you the ASCII for 'a' or 'A' and then asked the bit pattern for a string of letters.)
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    (Original post by ShatnersBassoon)
    A piece of hardware used to connect a device to a wireless network. Most modern day routers will contain a wireless access point, but a WAP can also be a separate device e.g. large offices may need several WAPs connecting to the same router to cover the whole area of the office.

    Basically what it sounds like. It allows a device to connect to a wireless network. As far as I can tell, devices like laptops have built in WNAs but if you wanted to (for example) connect a desktop PC to WiFi you would need a USB wireless network adapter.

    So first, the reason that wireless networks are less secure than wired networks is because they communicate by sending electromagnetic signals through the air, and these signals can be intercepted much more easily than a signal through a wire. The way they can be secured is with the following:
    • Use WPA/WPA2 (WiFi Protected Access), a protocol which uses a very secure method of encryption.
    • Disable broadcast of your SSID (the identifier for the network).
    • Use a MAC address whitelist (see below).

    A whitelist is the opposite of a blacklist - while a blacklist contains the things that are not allowed, a whitelist contains the things that are allowed. In this case, the things being listed are MAC addresses - numbers assigned to each physical device (hard-coded into its Network Interface Card). So you specify the devices you want to be able to connect to the network (e.g. your desktop, your laptop and your iPad) and only these devices will be allowed to connect to the network.
    God bless you


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