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AQA COMP3 June 2012 Exam Thread

Reply 300

TB.93

1

Does anyone know the difference between a proxy server and a firewall?

Reply 301

gowans07

Original post by rikin

Yeah i guess so, im gonna have a long day learning this glossary at the back of the book :/ Whats worse is i have another exam to revise for the next day :/

Try two exams on one day! Both two and a half hours !!

This was posted from The Student Room's iPhone/iPad App

Reply 302

gowans07

Original post by TB.93

Does anyone know the difference between a proxy server and a firewall?

Ones incoming connections and the other is outgoing

This was posted from The Student Room's iPhone/iPad App

Reply 303

mujahid_e3

can anyone explain binary trees to me. i keep getting it wrong. How are you meant to know which goes on the left subtree and which goes on the right om very confused.
:s-smilie:

Reply 304

TB.93

1

Original post by gowans07

Ones incoming connections and the other is outgoing

This was posted from The Student Room's iPhone/iPad App

Sorry still don't understand :/

Reply 305

SecondHand

Original post by mujahid_e3

can anyone explain binary trees to me. i keep getting it wrong. How are you meant to know which goes on the left subtree and which goes on the right om very confused.
:s-smilie:

If the item is greater than the parent then it goes in the right, if it is less than it goes in the left.

Reply 306

username775070

3

Original post by TB.93

Does anyone know the difference between a proxy server and a firewall?

Original post by gowans07

Ones incoming connections and the other is outgoing

Original post by TB.93

Sorry still don't understand :/

That is because it is incorrect. Strictly speaking, the textbook refers to a firewall as a hardware device or program that controls traffic between a private network and the internet. There are two types of firewall methods:

1. Packet Filtering - incoming packets are checked against a list of filters and are either allowed or blocked.
2. Proxy Server- when a user of a private network requests information from the internet, the proxy server retrieves the information and filters it, before passing it onto the requesting computer. Thus, the user's computer does not come into direct contact with the web server/web page.

Reply 307

TB.93

1

Original post by joenye

That is because it is incorrect. Strictly speaking, the textbook refers to a firewall as a hardware device or program that controls traffic between a private network and the internet. There are two types of firewall methods:

1. Packet Filtering - incoming packets are checked against a list of filters and are either allowed or blocked.
2. Proxy Server- when a user of a private network requests information from the internet, the proxy server retrieves the information and filters it, before passing it onto the requesting computer. Thus, the user's computer does not come into direct contact with the web server/web page.

So a proxy server is a type of firewall. So when you go on YouTube at school and it says access denied that's a proxy server?

Reply 308

BalletDystopia

Okay new question. Not sure when to use Procedures/Functions in OO questions. If there's just procedures in the example they usually give just use procedures? They sometimes throw in functions as well as procedures too. Which one do you use and why? Cheers!

Reply 309

exe

Original post by TB.93

So a proxy server is a type of firewall. So when you go on YouTube at school and it says access denied that's a proxy server?

no, a proxy is where a server acts as an intemediary between the client and another server. all packets are routed htrough the proxy to the client, so the only thing the server comes into contact is the proxy.

Reply 310

Chrisaster

Original post by TB.93

So a proxy server is a type of firewall. So when you go on YouTube at school and it says access denied that's a proxy server?

That's an example of a proxy server, yes. All traffic goes through the proxy server the school uses and if it's coming from or going to a blocked website (e.g. YouTube) then it'll show the blocked page instead.

Reply 311

SecondHand

So when I try to access Youtube at school and my school has a proxy server what does that mean?

Reply 312

username775070

3

Original post by SecondHand

So when I try to access Youtube at school and my school has a proxy server what does that mean?

It means the URL was checked on the school's server first, and that server checked for blocked content (e.g. flash video, the word 'YouTube', etc). It is simply a proxy server, as I and others have explained.

By the way, you don't need to know in that much detail at all. I suspect, it will only be 1 or 2 marks.

Reply 313

Chrisaster

Original post by SecondHand

So when I try to access Youtube at school and my school has a proxy server what does that mean?

The general process is:

1) Client machine sends a HTTP request to proxy server containing the desired URL.
2) Proxy server reads the domain name in the URL and checks if it's in the list of blocked URLs.
3) If it is, the proxy server redirects the client to the blocked page.
4) If it isn't, the proxy server forwards the client's HTTP request to the requested web server, the web server responds and the proxy server forwards this response to the client, displaying the web page.

So, if you tried to go to YouTube and it was blocked..

1) Client sends a HTTP request for youtube.com to the school's proxy server.
2) Proxy checks for youtube.com in the list of blocked URLs.
3) It's in the list, so redirect the client to the blocked page.

Reply 314

gowans07

Original post by BalletDystopia

Okay new question. Not sure when to use Procedures/Functions in OO questions. If there's just procedures in the example they usually give just use procedures? They sometimes throw in functions as well as procedures too. Which one do you use and why? Cheers!

Function is usually used when retrieving a single item such as Function GetPlayerName

Procedure is used as a collection of details so Procedure PlayerDetails.

This was posted from The Student Room's iPhone/iPad App

Reply 315

dc94

I don't fully understand SQL queries...

I thought the tables listed after 'FROM' should only be the tables containing the attributes referenced after 'SELECT' but doing question 6d of June 2010 shows that more tables are used and I don't understand why. Can anyone help me out with this?

Reply 316

Chrisaster

Original post by dc94

I don't fully understand SQL queries...

I thought the tables listed after 'FROM' should only be the tables containing the attributes referenced after 'SELECT' but doing question 6d of June 2010 shows that more tables are used and I don't understand why. Can anyone help me out with this?

The tables after 'FROM' are all the tables that will be used in the query. In that question, attributes are also accessed using the 'WHERE' statement.

Reply 317

Edwin Okli

3

Original post by BalletDystopia

Okay new question. Not sure when to use Procedures/Functions in OO questions. If there's just procedures in the example they usually give just use procedures? They sometimes throw in functions as well as procedures too. Which one do you use and why? Cheers!

I think in general terms: functions return values and procedures do not. So, a get method is a function and a set method is a procedure.

Are we all expecting OOP to come up again this year? I was surprised that it wasn't on last year's paper; AQA seem to stress its importance.

Reply 318

dc94

Original post by Chrisaster

The tables after 'FROM' are all the tables that will be used in the query. In that question, attributes are also accessed using the 'WHERE' statement.

Ah thanks a lot, I get it now.

Reply 319

skeletonboy

How much SQL, DDL, DML will we actually need to know? Will we need to create databases? Add users and grant permissions? Complex queries?

AQA COMP3 June 2012 Exam Thread

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