CS

Subdecks (4)

Cards (59)

  • Components of the CPU
    • Control Unit (CU)
    • Arithmetic Logic Unit (ALU)
    • Cache
    • Registers
  • Control Unit (CU)
    Controls the flow of data in and out of the CPU<|>Manages and co-ordinates all of the Fetch-Decode-Execute cycle
  • Arithmetic Logic Unit (ALU)

    Carries out the mathematical calculations<|>Logical operations and binary shifts
  • Cache
    Stores frequently and recently used data and instructions for quick access<|>Faster read-write speed than RAM but not faster than the registers
  • Registers
    Single piece of memory with a value<|>Temporarily holds addresses, instructions or data<|>Fastest read-write speed
  • Stored Program Concept
    In the Von Neumann Architecture, both the programs and the data they use are stored in memory
  • Purpose of the CPU
    To repeatedly execute instructions stored in memory<|>(To carry out the Fetch-Decode-Execute Cycle)
  • Registers used by the CU to run Fetch-Decode-Execute Cycle
    • MAR - Holds address of data to be fetched/stored
    • MDR - Holds data/instructions fetched from memory
    • PC - Holds address of next instruction to be processed
    • ACC - Stores results of calculation done by ALU
  • Fetch-Decode-Execute Cycle
    1. Fetch: Memory address copied from PC to MAR, CU fetches data/instructions from RAM, Data copied to MDR, PC incremented
    2. Decode: CU decodes the instruction in MDR
    3. Execute: Instruction carried out (e.g. calculation in ALU, loading from memory, writing to memory)
  • Clock Speed
    Number of Fetch-Decode-Execute Cycles per second<|>Every action in CPU takes place on the tick of a clock<|>The higher the clock speed, the more Fetch-Decode-Execute Cycles done in a second<|>Measured in Hertz (Hz)
  • Cache Size

    Cache is much faster than RAM<|>Data goes in and out much quicker<|>Recently and regularly used data is stored here<|>Makes CPU efficient as less time is wasted in waiting for data to be transferred
  • Number of Cores
    A processor can have more than one core<|>Each core can process Fetch-Decode-Execute Cycles simultaneously<|>But only if the software is designed for multi-core processors
  • Embedded Systems
    Used to control the function of electronic devices<|>Perform limited and very specific tasks<|>Their input is often controlled by a button/switch<|>It's a computer system embedded within a device<|>Designed for a specific purpose on circuit boards
  • Primary Storage
    • RAM - Stores programs currently being used, copies data needed by programs, stores instructions/modules from open programs
    • ROM - Can store data without power, stores boot sequence instructions, can only be read, not written to
  • Virtual Memory
    Used when there is not enough space in RAM for programs and data that is currently being worked on<|>It's a small section of secondary storage<|>It acts like RAM<|>When the program in virtual memory is required, it is swapped with something not in use in RAM<|>The process of swapping will take time as hard disk speeds are much slower
  • Secondary Storage
    • Magnetic Storage - Uses different patterns of magnetisation in a tape/hard disk to store data
    • Optical Storage - Marks arranged in patterns, laser burns 'pits' into shiny surface
    • Solid State Storage - Sends a large electric current to force electrons through barrier and trapping them in position
  • Characteristics of Storage Media
    • Capacity - The amount of memory the medium has / how much data it can store
    • Speed - How quickly the data can be accessed from it
    • Portability - Whether the medium can easily be moved from one computer to another
    • Durability - How strong the medium is & how many times it can be reused before it fails
    • Reliability - How consistently it records and plays back data over time / retains quality
    • Cost - Relative as there are many types of any one device and medium
  • Suitability of Storage Media
    • CDs & DVDs - Useful for keeping data for later use
    • Memory sticks - More effective for more regular backup
    • HDDs - Mainly found on desktop computers
    • SSDs - Frequently used for operating system & software that need to be fast, require very little power, no moving parts so don't heat up much, very thin and reliable, perfect for small portable devices with built-in storage
  • Binary
    All characters on the keyboard are represented by a binary number<|>These binary numbers are patterns of 0 and 1
  • Character Set
    All the characters that can be represented on a computer by a binary number<|>Or a defined list of characters represented by a binary number on a computer
  • ASCII
    Is an example of a character set<|>It consists of 128 characters, using 7 bits<|>ASCII codes are alphabetically ordered, so it's possible to figure out one code from another
  • Extended ASCII (EASCII)
    It consists of 256 characters, using 8 bits<|>Additional characters in the set include symbols, other languages and mathematical characters
  • Unicode
    It consists of 16, sometimes 24, sometimes 32 bits<|>This exponentially increases the number of combinations possible<|>It can represent more characters including ones from all other languages, symbols and emojis