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Comp Sci 1 - Final Exams - Coggle Diagram
Comp Sci 1 - Final Exams
1.1
1.1.1
FDE:
- Instructions are fetched from RAM / main memory.
- Instructions are decoded by the control unit.
- Instructions are executed (perhaps by the ALU).
- Program counter increments by one.
- The cycle repeats.
Common CPU Components:
- ALU: Performs any calculations or logic decisions in the CPU.
- CU: Controls how data is transferred and managed within the CPU, it does this using read-write cycles (also controls timings).
- Cache: Small store, commonly used..., faster to access than the RAM.
- Registers: Small, fast, temporary data stores with a specific purpose.
Registers:
- MDR - Holds the data that is to be transferred to main memory.
- MAR - Holds the address of the instruction that has just been fetched from memory.
- ACC - Holds the result of any calculations or logic decisions performed by the CPU.
- PC - Holds the address of the next instruction that is to be retrieved from or written to memory.
1.1.2
Factors Affecting CPU Performance:
- Clock Speed: Number of instructions that can be executed per second.
- Cache Size: Amount of commonly...
- Num of Cores: Number of instructions that can be executed simultaneously.
1.1.3
Embedded systems are smaller systems within a larger system with a designated purpose. Examples include:
- GPS systems.
- Central heating systems.
- Fitness trackers.
1.2
1.2.1
Primary storage is used to store data in a volatile manner (holds data that the CPU needs to access when the computer is running). Primary storage typically has much faster access speeds than secondary storage
RAM:
- Typically a larger capacity.
- Read and write (contents can be changed).
- Stores currently...
- Volatile.
ROM:
- Smaller capacity.
- Read only.
- Stores the bootstrap and the BIOS.
- Non-volatile.
Virtual memory is made use of when the RAM is full, it is stored in secondary storage and stores not currently... but running programs directly from virtual memory is slow. They should be moved back to primary storage first.
1.2.2
- Optical: DVD-R, DVD-RW, Blu-Ray
- Magnetic: Floppy Disk, Hard Disk Drive
- Solid State: SSD, Flash Memory, Flash drive
- Optical: Low capacity, slow access speeds, portable, easily scratched, easily distributed, low cost per GB.
- Magnetic: High capacity, relatively fast access speeds, not very portable due to moving parts.
- Solid State: Typically high capacity, fast access speeds, high cost per GB, portable, limited read-write cycles.
1.2.3
1MB = 1,000,000 Bytes
1GB = 1,000,000,000 Bytes
1TB = 1GB x 1000 Bytes
1PB = 1TB x 1000 Bytes
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1.2.4
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Sounds are converted from an analogue form to a digital form through taking a number of samples per second and representing this sample with a binary value.
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1.2.5
- Lossy: Reduced to a greater degree, data is lost but this is often unnoticeable.
- Lossless: Reduced to a lesser degree, can be converted back to original, no data lost, uses repetition techniques.
1.3
1.3.1
- Bandwidth: Amount of data that can be transferred at once.
- Number of users: More users/traffic will slow the network down if there is insufficient bandwidth.
- Error rate: Amount of packets that have to be resent per second. Dependent on material length and grade.
- Latency: Delay between sending data and receiving it, caused by bottleneck in the network infrastructure
- Transmission media: Differ in bandwidth.
Client-Server:
- [+]:
- Easier to manage backups of all shared data.
- Easier to manage security of files.
- Easier to install software onto all connected devices.
- [-]:
- Can be expensive to set up and maintain.
- Requires IT specialists to maintain.
- Server is a single point of failure.
- Nodes will lose connection to the network if the server fails.
Peer-To-Peer:
- [+]:
- Easy to maintain, no specialist staff required.
- No dependency on a single device.
- Cheaper start-up costs.
- No expensive hardware (server) required.
- [-]:
- The network is less secure.
- Users are responsible for managing their own backups.
- Can be difficult to maintain a well-ordered file store.
LAN Hardware:
- NIC: Allows for devices to connect to a LAN, the MAC address of the device is stored on here. It uses a protocol to govern how this connection should work.
- WAP: Allows for devices to connect to a wireless network. This is more convenient as devices can be more mobile but the bandwidth is lower. Security is more of a concern with these connections.
Advantages of the Cloud:
- Can be accessed at any time from anywhere with an internet connection.
- Can be accessed from any device.
- Large capacity.
- Automatic backups.
- Makes online collaboration easier.
Hosting is the storing of files on a web server, allowing for 24/7 access, a greater number of users and greater security.
Star:
- Centralised switch.
- If a single cable breaks, one device will no longer be able to access the network.
- Switch is a single point of failure.
Mesh:
- Every device connected to every other device.
- More expensive due to more cabling.
- Devices remain unaffected if one cable breaks.
1.3.2
Wireless:
- Users can move devices around freely.
- Less expensive to set up.
- Can handle a large amount of users.
- Convenience.
- Slower transfer speeds.
- Less secure.
- Signals can be obstructed.
IP Addressing:
- Routes packets on a WAN, written in denary, dynamic.
MAC Addressing:
- Routes packets on a LAN, unique to every NIC, written hex, static.
Standards are specifications for hardware and software that make it possible for manufacturers create products that are compatible with each other. Examples include: ASCII, HTML and file identifiers.
Layering divides the networking process into smaller, simpler tasks that work together. Each layer has a defined responsibility and provides a service to the layer above it. Advantages include:
- Reducing complexity through breaking into subproblems.
- Devices can be made to operate at specific layers.
- Products from different vendors can work together.
Common protocols:
- TCP/IP - Allows for error free communication between routers on a WAN.
- HTTP - Allows for sending or requesting of webpages from a web server.
- FTP - Allows for the transfer of files between devices on a network.
- SMTP - Allows for emails to be delivered to a mail server.
- POP - Retrieves emails from a mail server by removing them.
- IMAP - Retrieves emails from a mail server by creating a copy.
1.4
Malware:
- Firewall
- Spam filter
- Updating OS
- Regularly backup files.
DDoS:
- Strong firewalls
- Packet filters
- Network forensics
- Storing data on the cloud
Brute force:
- Progressive delays
- Strong passwords
- Challenge response
Data interception:
- Encryption
- Use of virtual networks
- Training staff
1.5
1.5.1
The OS provides the interface between the user and the hardware + provides a platform on which application software can run.
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The OS also manages memory, files and device drivers.
Multitasking occurs when the processor allocates a small amount of time to each process, making it appear that both processes are happening simultaneously.
Device drivers translate the OS's instructions into instructions that can be understood by the hardware.
1.5.2
Defragmentation reduces the movement of the read/write head which speeds up file access. Solid state devices do not need to be defragmented, it could reduce their lifespan.
1.6
Computer Misuse Act 1990:
- Hacking.
- Fraud.
- Deliberate damage.
- Planting viruses.
- Data theft.
Data Protection Act 2018:
- Processes lawfully.
- Collected legitimately.
- Relevant and limited.
- Kept Updated.
- Only held for as long as necessary.
- Not given to countries with unsatisfactory data protection laws.
Open source:
- Users can modify and distribute.
- Support by community.
- Access to source code.
- May not be fully tested.
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