Computer science -paper 1

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Cards (41)

  • The CPU is the central processing unit, it carries out program instructions using data
  • Components inside the CPU
    • ALU (Arithmetic Logic Unit)
    • Control Unit
    • Cache
    • Registers
  • ALU
    Carries out maths and logic needed to execute instructions
  • Control Unit

    Coordinates the fetch-execute cycle and decodes instructions
  • Cache
    Small, fast memory that holds frequently accessed items
  • Special purpose registers

    • Memory Address Register (MAR)
    • Memory Data Register (MDR)
    • Program Counter
    • Accumulator
  • Fetch-Execute Cycle
    1. Fetch instruction from memory using Program Counter
    2. Decode instruction
    3. Execute instruction, possibly fetching data
  • Clock speed
    Rate at which the fetch-execute cycle is carried out, in GHz
  • CPU performance factors

    • Clock speed
    • Number of cores
    • Cache size
  • Embedded systems
    Computers built into other devices, with one specific purpose
  • Types of storage

    • Primary (RAM, ROM)
    • Secondary (HDD, SSD, optical)
  • RAM
    Volatile memory, contents lost when power is off
  • ROM
    Non-volatile memory, contains startup program
  • Secondary storage types
    • Hard disk drives: reliable, large capacity, fragile
    • Optical discs: portable, reliable, fragile
    • Solid state drives: fast, durable, expensive
  • Binary units

    • Bit
    • Nibble
    • Byte
    • Kilobyte
    • Megabyte
    • Gigabyte
  • Binary addition
    1. Carry 1 to next column for 1+1
    2. Carry 1 for 1+1+1
  • Binary shifts

    1. Left shift: double the number
    2. Right shift: halve the number
  • Overflow error

    Result takes up more storage space than is possible
  • Character sets
    • ASCII: 8-bit, 256 characters
    • Unicode: 16-bit+, supports many languages