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February Comp Sci Test - Coggle Diagram
February Comp Sci Test
Systems Architecture
The control unit is responsible for the flow of data through the CPU, it does this using read-write cycles.
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Registers are small, fast stores of data within the CPU that are used during processing.
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Examples of embedded systems include central heating systems, traffic lights and GPS systems.
Memory and Storage Pt1
ROM: Read only, stores the BIOS and Bootstrap, contents cannot be changed.
RAM: Read and write, stores currently used..., contents can be changed.
Virtual memory is used when the RAM is full, running programs from virtual memory is much slower than running them from RAM.
Factors Relating to Secondary Storage:
- Capacity
- Speed
- Portability
- Durability
- Reliability
- Cost
Memory and Storage Pt2
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ASCII: 2^7 (2^8 for Extended), does not account for foreign languages.
Unicode: 2^32, can represent foreign languages also.
For an analogue sound to be represented in binary, samples of the sound are taken in a given time period; these samples are converted to a binary value.
Computer Networks
Bandwidth: Amount of data that can be successfully sent and received in a given time.
Latency: The delay between transmitting data and receiving it; this is caused by bottlenecks in the network's infrastructure.
Error rate: The number of packets that have to be resent in a given time; determined by the length/grade of the transmission media or environmental factors.
Advantages of Networks:
- Allows for sharing of peripherals.
- Allows for sharing of files.
- Security and software updates can be managed on devices simultaneously.
- Allows for communication between devices.
A URL is the unique web address for a webpage on the internet, it is written in characters.
An IP address is a dynamic address used to identify the unique location in which you are connected to the internet. It is written in denary (in IPv4 or IPv6). It is used to route frames on a WAN.
MAC addresses static addresses that are used to identify the location of a device on a local area network and route packets on the network. It is stored in hexadecimal, this is done in order to make much larger numbers look smaller.
Features of Servers:
- Controls access and security to one shared file store.
- Manages access to the internet.
- Manages printing jobs.
- Provides email services.
- Runs a backup of data.
- Client requests services and the server provides them.
Pros and Cons of Client Server:
+:
- Easier to manage security of files.
- Easier to take backups of shared data.
- Easier to install software to all devices.
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- Can be expensive to set up and maintain.
- Specialist staff may need to be hired.
- Server is a single point of failure.
Pros and Cons of Peer to Peer:
+:
- No specialist staff required.
- No dependence on a single device.
- Cheaper to set up.
-:
- Network is less secure.
- Users need to manage their own file backups.
- Can be difficult to maintain an ordered file store.
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Wi-Fi:
- Users can move around freely.
- Easier to set up and less expensive.
- Convenient to use.
- Can handle a large number of users.
- Less secure than wired.
- Speeds are slower than wired.
- Signal can be obstructed.
Network Security
Brute force: Trial and error approach of guessing passwords to gain unauthorised access. Progressive delays, two factor authentication, more secure passwords.
DDoS: Overloading a server with illegitimate requests in hopes of making the server unable to process legitimate requests. The use of network forensics and implementing a firewalls.
SQL Injection: The input of malicious code into a text box to modify, retrieve or delete data. Prevented with parameter queries, banning certain characters, input sanitisation and validation.
Malware: Malicious software used to change or delete data (cause harm). Anti-malware software, user level access, good network policies.
Data Interception and Theft: The process of intercepting packets travelling on a network in an attempt to read them. Encryption, hashing data.
Social Engineering: The use of people as a weak point in a network. Anti-spam filter, staff-training implemented, network policies implemented.
Systems Software
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An operating system:
- Manages the activities of the processor.
- Multitasks.
- Manages memory.
- Manages peripherals.
- Organises/manages files.
- Provides security and utilities.
Multitasking is done through the processor allocating a small slice of its processing time to each task; this gives the appearance that more than one task is being done at one time.
Device drivers translate instructions from the operating system into commands that the connected device can understand.
Examples of utility software include:
- Defragmentation - A fragmented disk takes longer to read and write from.
- Compression - Makes files easier to transmit across a network.
Encryption - Prevents those with unauthorised access from reading transmitted files/packets.
Computational Thinking
Advantages of decomposition:
- Makes problems easier to solve.
- Different people can work on different parts simultaneously.
- Reduces development time.
- Program components from one program can be easily used on another.