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Hardware - Coggle Diagram

- - - - Read only Memory
        
        It is used to start the computer
        
        It is non-volatile so it does not get deleted
      - Not easy to alter or reprogram the ROM
    - - Random access memory
      - Volatile so requires power to store
      - Stores the data and programs currently being used by the computer
      - Contents constantly being changed
      - You can add more storage by adding more sticks of RAM
  - - - Optical (1982)
        
        Uses lasers to store data
        
        People thought it would replace hard disk drives but they could not be produced with a high enough capacity. They are cheap, fragile and can be used to physically mass distribute data.
        
        lasers burn information onto a circular disk. Read and write heads move acrosss the surface. Has pits on it in a spiral track surface between each pit is called a land
        
        DVD
        
        Blu-ray
        
        Cd
      - Magnetic
        
        Uses the properties of magnetism to store data
        
        Usually uses spinning magnetic plates called platters they spin to read and write data
        
        The plates have tracks sectors. It uses an electromagnet to magnetise dots on the platter. If they are magnetised they have the binary value 1 if they aren't magnetised they have a binary value of 0. Each platter has billions of the dots.
        
        Hard disk drives: The first ones were very expensive
        
        Floppy disk
        
        hard drives
        
        Zip drive
      - Solid-state storage
        
        Uses transistors to store data
        
        They can be wired in different ways
        
        NOR flash structure
        
        Cells are wired in a parallel structure
        
        NAND flash structure
        
        Cells are wired in series
        
        Control gate: controls the flow of electrical current
        
        floating gate: stores electrical current
        
        The control gate sits on top of the floating gate
        
        Doesn't have moving parts
        
        Uses semi conductor chips
        
        Data is flashed onto chips
        
        contains cells and transistors laid in grid. Can be wired in different wired in different wires
        
        When the SSD is first created all the transistors are set to binary value 1
        
        When the data is stored on the transistor after it has gone through the control gate the transistor is set to 0
        
        a solid state drive is an example of a solid state storage device. A USB stick is another example
        
        Virtual Memory
        
        Used on secondary storage devices when there is a shortage of memory in the primary memory (RAM) it is therefore created for temporary use
        
        Virtual memory is created in a computer system with a hard drive component being sectioned the data that travels too and from the RAM to the virtual is called a page. If there is only space for 3 pages and a page isn't currently need it will be stored in virtual memory
  - - - You don't have to pay for expensive hardware or have redundant hardware that you have paid for that you don't need
      - You aren't responsible for the security of the data
      - As long as you have network connection you can access the data anywhere
      - You can easily increase and decrease storage space
      - You don't need to constantly maintain an update security
    - - You don't have to rely on internet connection
      - you don't have to rely on a 3rd party tom keep your data safe
    - - In order to connect to the cloud to access your data you need to have a connection to the internet
        
        You do this through a network of connected devices.
        
        The NIC (network interface card)
        
        it can be wired
        
        uses cables plugged into the network
        
        it can be wireless
        
        Most modern ones are wireless
        
        Most important feature is the MAC address (media access control): A unique address given to the NIC by the manufacturer
        
        It enables every NIC to be identified individually
        
        made up of an ID and serial ID
        
        This creates a unique code in hexadecimal as the Mac agrees. Its is in hexadecimal as it is a large number. 6 pairs of numbers separated by a colon
        
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        A router has one because it is part of a network
        
        A router sends data packets through their IP address
        
        IP4 structure
        
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        IPV6 structure
        
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        static: doesn't change when the device is turned on and off
        
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        Dynamic: changes each time it is connected to the network
        
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- - - - Execute: Where the instruction is executed by the CPU
      - The instruction set is examined by the control unit (CU) Instruction set: a set of commands that can be processed by a certain CPU
        
        Fetch Stage: In this stage the operations that are conducted involve the ALU this is a special purpose register which performs all the calcualtions necessary the results of the calculation are stored in a general purpose register called the accumulator
    - - The RAM (this is where the instructions are stored) the stored program concept
        
        Von Neumann architecture use in all computers. For in striations to be processed they need to be brought from the Ram to the CPU
        
        The first register that is involved in the fetch stage is called the program counter (PC) The program holds the address of the instruction in the RAM
        
        The program counter needs to be transported We use the address bus to do this. It uses wires for transmission of addresses between components
        
        The transmitted address from the PC via the address bus is sent on a special register called the memory address register (MAR) Once the address has arrived in the MAR it is sent via the address bus to the RAM
        
        The instruction from Ram is sent via the data bus into a special purpose register called memory data register/memory buffer register MDR/MBR
        
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