Hardware Devices (Cambridge (CIE) A Level Computer Science) : Revision Note

Device operations

Magnetic hard disk

• A magnetic hard disk is made up of several metal discs coated with a magnetic material

  • These are called platters

  • Iron particles on each platter are magnetised to represent a 0 or 1

• Each platter is divided by concentric circles creating several tracks and wedge shaped sectors

• Where they intersect is a track sector

• The hard drive spins the metal disk(s) at a high speed (typically around 5400-7200 RPM) using a motor

• A read/write arm, controlled by an actuator, moves the head over the surface of the disc to the location of the data

• The data is read/written using electromagnets

Solid state (flash) memory

• Examples of solid state storage devices include:

  • Solid state drives (SSD) - replacing magnetic hard drives as a computers primary secondary storage device as capacity increases and cost decreases

  • USB flash memory - most common form of portable storage device

• It uses NAND and NOR gates in electrical circuits to persistently control the flow of electrons

• Solid-state (flash memory) is memory made up of tiny cells that can contain one bit of data (1 or 0)

• Each cell contains a transistor that acts as a switch that can be turned on or off

• The transistor contains two main parts:

  • Control gate - top layer of transistor, connects to circuit and controls if current can flow through the transistor

  • Floating gate - can hold a charge (like a tiny rechargeable battery) and is sandwiched between two layers of insulating material (Oxide)

• To store data a charge is placed on the floating gate

  • A high voltage is applied to the control gate, which allows electrons to be pushed through the oxide layer and onto the floating gate

• To remove data, a high voltage charge is applied in the opposite direction, pulling the electrons off the floating gate

Optical disk reader/writer

• Examples of optical storage include:

  • Blu-rays have the largest capacity

  • CDs have the lowest capacity

  • CD-R are read-only (you cannot save data on to them)

  • CD-RW can be written to and read from

  • DVD-RW can be written to and read from

• All optical devices work by shining a laser at the disk and processing the reflection

• An arm moves the laser across the surface of the disk

• In CD-Rs a laser burns the data, permanently on to the disk, by creating pits and lands

• The laser is also used to read the data from the pits and lands

• When the laser light hits the point where the pit changes into a land or vice versa the light scatters and is not reflected back as well.

• This is captured by a sensor and can be interpreted as a change in the binary value

Laser printer

• Laser draws the image

  • A laser beam draws the page onto a photosensitive drum

  • Wherever the laser hits, it changes the electric charge on the drum

• Toner sticks to the drum

  • Toner powder is attracted to the charged areas

  • These areas match the shape of your text or image

• Toner is transferred to paper

  • The drum rolls the toner onto the paper

  • This creates a perfect copy of your page

• Fusing

  • The paper goes through hot rollers

  • This melts the toner onto the paper so it doesn’t smudge

3D printers

• Builds objects layer by layer from the bottom up

• Great for complex shapes that traditional methods can’t make easily

• Uses different materials like:

  • Thermoplastics

  • Resins

  • Metals

• Common types of 3D printing include:

  • FDM (Fused Deposition Modelling) – melts plastic and builds in layers

  • SLA (Stereolithography) – uses light to harden liquid resin

• Used in healthcare for custom prosthetics

• Used in automotive and aerospace for bespoke parts

• Allows for high customisation and rapid prototyping

• Can be slow to print large or detailed objects

• Some methods need special materials that can be expensive

Microphone and speakers

Microphones – input device

• Convert sound waves into electrical signals

• Let users record voice or send audio into a computer

• Types of microphones:

  • Dynamic microphones – good for loud environments (e.g. concerts)

  • Condenser microphones – more sensitive and accurate, used in studios

Speakers – output device

• Turn electrical signals back into sound waves we can hear

• Range from:

  • Basic single speakers (e.g. built into laptops)

  • To multi-driver systems (e.g. home theatres) that handle different sound frequencies

• Found in phones, laptops, studios, smart devices, home theatres and more

• Have improved with digital sound processing and smaller components

• Support interactive communication like voice commands, calls, and multimedia playback

Touchscreens

• Detect a user’s touch and turn it into an input command

• Two common types:

  • Capacitive – reacts to the electrical charge in your finger (used in phones/tablets)

  • Resistive – responds to pressure (used in ATMs, tills)

• First used in ATMs and information kiosks

• Now used everywhere – smartphones, tablets, laptops, smart displays

• Popular because they allow direct, easy interaction

• Help make technology more accessible and intuitive to all users

Virtual reality headsets

• VR headsets create a fully immersive 360° digital environment

• Users can look around and interact with the virtual world

• Uses:

  • Head tracking

  • Motion sensors

  • Stereoscopic displays (3D vision)

• VR can be used in:

  • Gaming – realistic, interactive experiences

  • Education & training – safe environments for learning (e.g. surgery, pilot training)

  • Architecture & design – explore buildings before they’re built

  • Medical & therapy – pain distraction, exposure therapy, rehab

• VR can be challenging due to:

  • Expensive – headsets and powerful hardware can be costly

  • Comfort issues – long use may cause eye strain or motion sickness

  • Content creation – building realistic VR worlds takes time and skill