GSCE Computer Science

Cards (118)

  • what is the purpose of the CPU?

    to process data by following the fetch-decode-execute cycle, it's incharge of searching, sorting, calculating and decision making
  • what happens at the fetch stage?

    the CPU fetches data and instructions from RAM and then stores them in it's own temporary memory called registers
  • what happens at the decode stage?

    the CPU understands what the instructions mean, the CPU decodes the instructions and gets to the next step
  • what happens at the execute stage?

    the CPU carries out the instructions on the data
  • define bus

    information travels along a bus from one part of the CPU to another
  • define address bus

    a one way bus that requires data from an address in memory
  • define data bus

    moves data in both directions as data is both read and written to memory
  • define control unit

    responsible for timing on the CPU, uses the clock to ensure operations happen in the correct sequence
  • define arithmetic logic unit

    does all arithmetic calculations and logical operations
  • define registers

    Small temporary storage spaces inside the CPU
  • define accumulator

    stores the results from the ALU temporarily until they're written to memory
  • define program counter

    stores the memory address of the next instruction, is incremented by 1 at each new cycle
  • define instruction register
    current instruction is stored in this register
  • define memory address register
    stores the memory address of the current instruction being executed
  • define memory data register

    stores the data that was read/written to memory
  • what is the function of the ALU?

    performs basic arithmetic operations (addition, subtraction, multiplication, and dividion) and logical operations (AND, OR, NOT).
  • what is the function of the control unit?

    manages and monitors hardware, manages the input and output signals, uses clock signals to synchronise the running of the fetch-decode-execute cycle
  • what is the function of the cache?

    a small amount of storage that temporarily holds instructions that the CPU is likely to reuse, it's close to the CPU and so is fast to access
  • what are the 3 factors affecting CPU performance?
    clock speed, cache size, number of cores
  • How does clock speed affect CPU performance?

    the speed of the f-d-e cycle is determined by the CPU's clock chip, the clock speed is measured in hertz (cycles per second), the greater the clock speed, the more instructions are processed per second
  • what's the issue with increasing clock speed?

    the CPU can overheat (overclocking), so you need to use heat syncs
  • How does cache size affect the performance of the CPU?

    if the cache is larger it's more likely the next required instruction has already been transferred from the RAM to the CPU, improving process time
  • how does the number of cores affect the CPU?

    they can carry out parallel processing - the same program can have two instructions carried out at once. they can carry out multi-tasking - different program's instructions are carried out at the same time
  • what is an embedded system?

    An embedded system is a small computer that forms part of a larger system. it takes input, processes data and delivers an output. it doesn't need an operating system, the input is just a button or set a control, makes devices easier to use and increases reliability
  • what is primary storage? and examples

    memory areas that the CPU can access very quickly, has fastest read/write speeds, mostly volatile. eg. CPU registers, cache, RAM, ROM
  • what is secondary storage? and examples

    non-volatile where all data is stored when not in use, read/write speeds are much slower. eg. solid state, CD, SD cards
  • what is tertiary storage?

    used for long term data storage, mainly used for archives and backups of massive amount of data
  • what is RAM needed for?

    stores programs currently in use, helps to enable 'multi-tasking' (by copying data needed so it's passed through the CPU), stores all instructions from open programs
  • properties of RAM?

    volatile (loses data when no power), faster than hard drive, internal
  • how does RAM store data?

    uses capacitors and transistors, capacitor is a 1 or 0, transistors tell computer what's in capacitors
  • properties of dynamic RAM?

    1 transistor, 1 capacitor per bit, limit to how fast data can be read, power is always needed
  • properties of static RAM?

    4-5 transistors wired together for each bit data, doesn't lose its charge, much faster, but more expensive, needs constant power
  • what is the purpose of ROM?

    stores BIOS and boot up program
  • what are the properties of ROM?

    it's a memory chip, non-volatile (stores data without power), primary storage (directly accessed by the CPU), fast access rates
  • what type of memory do modern ROM chips use?
    flash memory
  • how does flash memory work?

    a large electrical current forces electrons through a barrier into fixed positions, the different arrangements give data
  • what is virtual memory?

    a small portion of secondary storage which acts as RAM in the event of the RAM becoming full
  • Why is virtual memory needed?
    it allows the computer to continue to function even though the RAM is full (albeit much slower)
  • what happens to the performance of the CPU with smaller/larger amounts of RAM?

    smaller = limited multitasking and greater use of slower virtual memory
    larger = greater storage of programs, faster performance, effective multi-tasking
  • what is cache memory?

    a small amount of memory located next to the CPU, it stores frequently used instruction, it supplies the CPU with data at high speeds