Topic 4 Computers

Mouse Keyboard Microphone Camera

Monitor Printer Speakers Vibration pack

All output is the result of inputs which have been processed, ie. Input -> Process -> Output

Control Unit Decoder Clock Arithmetic Logic Unit Cache Buses Registers

It can carry out 3 billion processing cycles per second.

Clock speed Cache Size Number of cores Size and type of RAM Hard drive speed

Programs and data stored in the same memory (RAM). Components are: • CPU • Program Counter • Memory • Input / Output

• Coordinates the actions of the computer. • Sends control signals to other parts of the CPU. • Contains the decoder which works out what the instructions mean

• Performs arithmetic and logical operations • Addition, subtraction,multiplication, division • Comparisons between two different numbers (eg , <= etc)

• Program Counter (PC) • Memory Data Register (MDR) • Memory Address Register (MAR) • Accumulator

Fetch: The next instruction to be executed is transferred from RAM into the CPU. Decode: The control unit (decoder) interprets the instruction. Execute: The control unit carries out the instruction. If calculations are needed, these are performed by the ALU.

RAM - Random Access Memory • Stores data and instructions while a program is running. -Main memory of the computer. • Volatile - data is lost if power turned off

ROM - Read Only Memory • Stores instructions to initialise hardware and load operating system • Data can only be read from ROM, not written to it • Non-volatile, data retained when power is off

• Very fast memory • Stores recently or frequently used instructions to speed up processing • Instructions don’t have to be fetched from RAM as often • Too expensive to use as RAM

• Magnetic discs • Optical discs • Solid-state (flash memory)

• Data/programs are stored permanently on secondary storage but cannot be accessed directly by the CPU. • They need to be loaded into RAM first. • RAM is volatile therefore cannot store permanently.

• Includes hard disc drives with large capacities • Consists of stacks of non-removable discs coated with magnetic materials • Discs spin and a read/write head moves across them • Data is encoded as opposing magnetic polarities on the surface • Using electromagnets in the read/write head

• Includes CDs/DVDs/BluRay • CDs store up to 700MB • DVDs store up to 4.7GB • BluRay discs store up to 50GB • Single spiral track on the disc • Data etched into the track as pits • Read by a laser

• No moving parts (unlike magnetic/optical) • Made of NAND flash memory • Non-volatile • Consists of floating gate transistors • Electricity is used to change the state of the transistors (0/1)

• SSDs (solid state drives in computers) • SD cards for use in portable devices like phones/cameras etc • USB flash drives (memory sticks)

• Off site storage - Made available to user over a network (usually the internet)

• Stored off-site so secure from fire/damage on-site • Can be accessed from anywhere with an internet connection • No need to buy expensive storage devices • Allows collaboration around the world • Data can be synced between a range devices (PC/Phone/Tablet etc)

• An internet connection is needed to access it • Download/upload speeds affected by the internet connection • Cloud company could be targets for hackers • Less control over your data as held by another company • Storing confidential data online may be in breach of legislation (DPA / GDPR)

A computer system built into another device in order to control it. Eg, Washing machine, microwave, digital camera