What does the application layer do?
The application layer creates a package of data with instructions on which program it’s for and how to interpret it.
What does the transport layer do?
The transport layer splits this package into little chunks (Packets) and labels them with where they’re going, where they came from and what order they’re in.
What does the network layer do?
The network layer is our routers and switches. They look at what the destination is and figure out where the packet should go next in order to get there as quickly as possible.
What does the MAR do?
Holds the address of the current instruction that is to be fetched from memory, or the address in memory that data is going to be transferred to.
What does the PC do?
Holds the memory address of the next instruction to be used, DOESN’T hold the address of the current instruction.
What does the MDR do?
Stores any data fetched from memory or any data that is to be transferred to and stored in memory.
What does the Accumulator do?
Stores results of any calculations made by ALU. Stores the values of inputs and outputs to and from the CPU.
What does the ALU do?
Carries out all the calculations and logical decisions required by the program instructions that the CPU is processing (e.g. add/subtract/”and”/”or”/”not”/ect).
What does the CU do?
Coordinates the activity of the CPU execute instructions. It sends out signals to control how data moves around the CPU and memory; and decodes instructions from memory.
What does the cache do?
Provides temporary, quick to access, storage for the CPU to access.
Unit order:
Bit -> Nibble -> Byte -> Kilobyte -> Megabyte -> Gigabyte -> Terabyte -> Petabyte
How many characters does ASCII have?
256
How many characters does UNICODE have?
More than ASCII (not all are used)
What is virtual memory?
Any data from a running program not currently being used by the computer can be temporarily moved from RAM to virtual memory
Advantages and disadvantages of ASCII:
Advantage: Takes up less storage space
Disadvantage: Can’t represent as many characters
Advantages and disadvantages of UNICODE:
Advantage: Can represent more characters
Disadvantage: Takes up more storage space
What is colour depth?
The number of bits used per pixel
What is resolution?
The number of pixels used per unit of distance- dots per inch (DPI)
How does encryption work?
Password is required, key used to scramble data, only devices without the correct password will be able to unscramble the data
What is TCP/IP - Transmission Control Protocol/Internet Protocol?
The fundamental set of rules that enables communication across the internet and private networks.
What is HTTP(S) - Hypertext Transfer Protocol (Secure)?
Defines the rules to be followed by a web browser/server when requesting and supplying data. (Secure)
What is FTP - File Transfer Protocol?
Defines the rules between for transferring files between a client and a server.
What is POP - Post Office Protocol?
Used by a client to receive emails from a mail server; the emails are downloaded to the device and deleted from the server.
What is IMAP - Internet Message Access Protocol?
Allows multiple devices to have synchronised access to mail on a mail server, messages are read rather than downloaded.
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Paper 1 - Computer Systems2
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About the Course3
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1.3 Computer Networks, Connections and Protocols and Protocols42
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n.w22
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GeorgeF30
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Dru <35
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ola2
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GeorgeM5
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jasmine >_< (and big G)7
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Network layers4
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Maimie29
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Freya3
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Bradley's deck1
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nicks deck1
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zachattack2
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hazzywazzy6
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Justas's deck3
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Endpoint revision6
