PPE Paper 1 & 2 revision

PPE Paper 1 & 2 revision

1. Data Storage

   • Sound
     • How sound can be sampled and stored in digital form
       • First, the sound is recorded by a microphone which makes it an analogue signal. Analogue signals are pieces of continually changing data. Secondly, Analogue signals need to be converted into digital data so the computer can read and store the sound in a file. This happens by analogue to digital converters, which are found in most modern recording devices. This Process of converting analogue signal into a digital signal is called sampling
     • The effect of sample rate, duration and bit depth.
       • To convert the analogue recording to digital data we sample the amplitude of the wave at regular intervals. The amplitude can only take certain values depending on the bit rate. Once sampled the device creates a digital curve.
       • Bit Rate = Sampling Frequency X Sample Size
     • Questions
       • 1.What is the equation for Bit Rate ?
       • 2.
   • Images
   • characters

2. Threats to computer systems and networks

   • Passive attack: It is where someone monitors data traveling on a network and intercepts any sensitive information they find.
   • Active attack: It is when someone attacks a software with malware or other planned attacks.
   • Insider attack: It is when someone within an organisation exploits their network access to steal infomation
   • Brute force attack: This is a type of attack which conserves of trying to guess the password over and over again until you get it right
   • Denial-of-service attack: This is where someone stop users from accessing one part of a website or network by flooding the servers with useless traffic
   • Malware: This stands for Malicious software that installs onto a users device with out them knowing

3. Client Server and Peer to Peer networks

   • Client Servers
     • The client server is managed by a server and other devices that connect to the server are the clients, All files are stored centrally on the server rather on the client device. The clients send requests to the server to ask if they can access the information they want and the server processes this and responds in the correct way. The server stores everything, for example: user profiles, passwords. However, you may need a certain access level to access the files you need so if you don't have the right access level the server will deny your request.
     • Pros: Easier to keep track of files. Easier to perform back-ups. Easier to install and update software. Easier to manage network security. Servers are reliable and are always on.
     • Cons: Expensive to set up and needs IT specialists to maintain. If the server goes down no client device can work. Server may come overloaded if too many clients try and get on at the same time
   • Peer-to-Peer networks
     • Peer-to-Peer networks don't use servers. In this network all client devices are equal and connect to each other. You can save files on a single device and share them with the other devices
     • Pros: Easy to maintain. No server dependence.
     • Cons: No centralised management. Back-ups are more complex. You can lose track of files. Devices are less reliable. Devive slows down when another device access the same file

4. Algorithms

   • Algorithms: Pseudocode
     • pseudocode isn't an actual programming language it just follows the structure carefully. the idea of it is that it make the algorithm's steps much clearer without worrying about the finer details of any programme language. there are lots of way to right pseudocode and they are all equally correct as long as the person who made it can understand it. So even though it isn't a actual coding language it is still useful because it make algorithm steps more readable and easy to interpret
     • A simple solutions would look like: Take worker's current salary multiply the salary by 1.1 display answer
     • A more useful solution would be: input salary, newsalary = salary x 1.1, output newsalary
   • Algorithms: Flowcharts
     • Every algorithm can be made into a flowchart, it's like another way to make it easier to understand algorithm steps like psuedocode does but in a different way. Flowcharts use different boxes for different commands
     • The start stop command is a command that uses a curved edged box and you need it at the start and finish of every algorithm
     • Inputs/ouputs command uses a trapezium box and is used to show things that has been either put in or taken out. E.g Input salary or Output new salary. They can also be used next to a decision box which helps them make a yes or no decision.
   • Arrays
     • An array is a data structure that can store a collection of data all under one name. A single piece of data is called an element, and each element can be accessed using it's position (or index) in the array Arrays a most helpful when you have lots of relevent data that you want to store in one place and the data also doesn't make sense to use a separate variable