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CS Summary - Coggle Diagram
CS Summary
Networks
Ring -> Each machine is connected to both its left and right. If one machine in the circuit breaks the information stored on that particular machine will be lost
Star -> Each machine is connected via a central server, if one machine goes down, no data is lost as its all stored on the central server
Bus -> Each machine is connected via a bus with a terminator at one side. If the bus breaks the whole network fails and no resources can be shared
Network -> A group of computers or machines which are linked together in order to share resources or information
ADVANTAGES : Share files and resources, Access files from any computer, Good communication with others
DISADVANTAGES: Increases security data as viruses spread more easy throughout the network. Computers may run slower if there's a lot of data being transferred
OS
Real Time -> Used to handle real time data supplied from something like a sensor, very fast and reliable
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Embedded -> An unchangeable and rigid operating system, usually installed in places like dishwashers or microwaves
An OS is software which manages software and hardware. It provides an interface for the user as well as utility software to keep the System running correctly
Processing
Distributed -> Intense and complicated tasks can be shared over multiple CPUS in order to be processed quicker
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SIMD -> Single instruction multiple dataset -> 1 Instruction , Multiple Data, Multiple Results
SISD -> Single instruction single dataset -> 1 instruction, 1 Dataset, 1 Result
Network security
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Proxies
Physical computers placed between network and outside, acts as an additional firewall
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Memory Management
Paging -> Data is broken down into fixed size pages, these are physical division that are transferred into memory when needed
Segmentation -> All different size logical divisions meaning complete sections of programs are not split up
Virtual memory -> Unused programs are sent to virtual memory in order to free up space in the RAM in order to handle new memory requests
Interrupts + Polling
Interrupts -> An interrupt is sent to the CPU when an external device needs attention. This is far more efficient than polling.
Polling -> The CPU will go round each connected device and check if it needs attention. If the device does not need attention it will move on to check the next device, this is very inefficient as time is wasted if a device does not need attention
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Encryption
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Assymetric -> 1 Pub key, 1 priv key
Compression
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Lossless -> Uses dictionary encoding or RLE in order to reduce redundant data and therefore reduce file size
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Protocols: TCP -> Communication over LAN/WAN (Transmission control Protocol)
HTTP -> Web Page requests
(Hypertext transfer protocol)
POP -> Email
(Post office protocol)
UDP -> Communication over LAN/WAN
(User Data Protocol)