2019/20 Computer Science AS Flashcards
Define Procedure
A procedure is a self contained set of commands that can be called from different parts of a program. They can be used for breaking code down into manageable sections (easier to read, debug and maintain), and preventing duplicating sections of code.
Difference between a constant and variable? Pros And Cons?
Constant= fixed value, variable= changes.
Constants: Value can’t be accidentally changed, the program will run faster, If value needs to be changed, it is easier to change it, as it only needs to be changed once.
Explain the bus topology and some advantages and disadvantages…..
Bus Topology:
All devices are connected to a backbone cable.
All devices have equal rights to the resources.
If more than 1 device tries to send data a collision occurs, where all devices withdraw the data they sent then a random timer is set (so they don’t keep colliding) and it tries again after a certain time.
Explain the star topology and some advantages and disadvantages…..
Star Topology:
Middle hub is surrounded by computers/ devices.
The switch reads the MAC addresses, and sends it to the appropriate device.
Downside= If the hub goes down the whole network won’t work.
Explain the ring topology and some advantages and disadvantages…..
Ring Topology:
Data travels in 1 direction in a “Token”.
No data collisions, as the token is the only thing that can take data around.
Each device will take the data and check if it’s for them, if it is, the token will change to read, go back to the user and then continue to be free, circling around again.
If the data is not for the device, the token will keep going round the loop, checking each device
What does NIC stand for & What does it do?
NIC= Network interface Card
Hardware which allows your computer to connect to the internet.
Explain The Client server Model….
Client Server model- 1 server in the middle that the computers access data from. Stores info such as user login.
Explain The P2P Network
P2P- No central server, users dedicate a portion of resources, Bandwidth, processing power etc, so each computer acts as a client and a server. Devices between the network have equal access, and this could be used in small offices, or in a small department of a large company.
What are 2 negatives to P2P Networking……
More access points for the outside world, so easier to hack
Everyone’s equal idea (no one can have more access rights)
Explain Packet switching
Packet Switching:
Data is split into packets, 500-1500 bytes, including a header to re order at the end. The packets take the fastest route possible, and are reordered at the end.
If data is intercepted, the hacker has not got all the data. Also, if a route is broken the packets can take a different route.
However the reordering takes time and it’s not good for small amounts of data, as the header takes up a lot of space.
Explain Circuit Switching
Circuit Switching:
Electronically connected
Doesn’t need a header and gets a dedicated line, and the full bandwidth.
However, the data is easier to intercept, as it isn’t split up, and a portion of the network is made unavailable while there is a connection.
An example of this is the old telephones (POTS).
What are the 3 types of storage?
Solid state, optical, and Magnetic
Define device Driver.
Device driver= Software that allows the device to operate
What is ROM?
Read Only Memory, where BIOS/ firmware is stored, non volatile.
What is BIOS?
BIOS= Basic Input Output System (Firmware), controls basic functions. The first thing to spring into action, waking everything up, checking settings.
Then it will run POST (Power On System Test) Then it will check for a drive with OS. MBR can only support up to 2 Tb (Master boot Record).
