3- Hardware

Memory Cache
Used to store the data which the processor needs for processing instructions.

Primary
Memory

RAM
ROM
It is the primary memory
unit which can be written It is the primary memory
to and from. unit which can be read
Stores the temporary from only.
apps running.

SRAM DRAM PROM EPROM

More efficient. Less efficient. Made up of a matrix Made up of floating
Slow. of fuses. gate transistors.
More fast.
Needs constant It can be Can be programmed
Doesnt need programmed once. more than once using
constant refreshing. refreshing.
Used in mobile UV light.
Expensive. Cheap.
phones. Used in developing
Consumes more Consumes less apps.
electricity. electricity.
Less storage. High storage.

Embedded Systems:

 Installation of microprocessors into devices to carry out operations.

 For example, controlling a heating system via mobile phones.

Advantages Disadvantages
 They are small.  They are difficult to upgrade.
 They are cheap to manufacture.  They are difficult to repair.
 They consume little power.  End up being thrown away (waste).
 They are reliable.  Open to hackers and malware.

Secondary Storage

HDD SSD
 Data is stored on concentric tracks.  Data is stored by controlling the
 Data stored via read and write operations; movement of electrons within the NAND
causes latency. chips in form of 0s and 1s.
 Slow data access.  Fast data access.
 Fragmentation of sectors causes  Expensive.
degradation.  Stores less data.
 Cheap.  Thin (portable)
 Store more data.  No mechanical parts.
 Fat

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CD DVD Blu Ray
 Data is stored on pits and  Data is stored on pits and  Data is stored on pits and
bumps. bumps. bumps.
 Uses red laser.  Uses red laser.  Uses blue laser.
 Uses a single 0.6mm  Uses dual 0.6mm  Uses a single 1.1mm
polycarbonate disc. polycarbonate discs which polycarbonate disc.
are sandwiched together.  More secure as comes with
 Larger storage than CD. encryption.
 More reliable.
 More storage.
 More expensive.

Laser Printer Inkjet Printer

 Uses dry ink.  Uses liquid ink droplets.
 Uses static electricity to print documents.  Uses nozzles spraying ink onto paper to
 Prints the whole document at once. print.
 Color dots are used to build the image.  Print the document line by line.
 Expensive.  Cheap.
 High quality print.  Low quality print.
 Fast.  Slow.

Working of Laser Printer:

 Data is sent from the computer to the printer buffer via the printer driver.
 The drum is given a positive charge.
 A laser removes the positive charges from certain areas.
 The negatively charged ink sticks to the positive parts of the drum.
 The paper rolls around the drum.
 It passes through a set of heated rollers.
 All of the charges are removed via discharge lamp.
Working of Inkjet Printer:

 Data is sent from the computer to the printer buffer via the printer driver.
 The print head contains the spray nozzles.
 The piezoelectric gives a charge to the nozzle which makes it vibrate which forces it to spray ink
onto the paper.
 The print head moves side by side along the paper until the whole document has been printed.
 Thermal bubbles (tiny resistors) are used to vaporize the ink.

3D Printing

Binder 3D Print Direct 3D Printing

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The objects are built up layer by layer by It is the same as Binder 3D printing except for the
materials such as powered resin, powdered metal, fact that it uses inkjet technology and moves left
paper or ceramic. to right and up and down to build layers.

Uses of 3D Printing:

 Make parts of items no longer in manufacture.

 Produce artificial limbs.
DAC (Digital to Analog Converter)

 It is used to convert digital signals in the form of 1s and 0s into an analog form.
 Used when computers give signals to an output device.
Working of a loudspeaker:

 Computers sends signals to speaker which are converted from digital to analog form via DAC.
 Signal passes through an amplifier which gives it enough current to drive a loudspeaker.
 The signal and current cause a cone and a coil to move up and down whose vibration produces a
sound.
Working of a microphone:

 It contains a diaphragm.
 It contains a coil and a cone which vibrate together when sound is received.
 This causes an electric current to be generated.
 Signals are generated which are converted into digital form from analog via ADC and stored in
the computer in the form of binary bits.
OLED Screens

 They are made of organic films which are sandwiched between 2 charged electrodes.
 They give off light when an electric field is applied to them.
Why to prefer OLEDs over LCDs:

 High resolution.
 No back lights.
 Less electric consumption.
 Thin.
 More color depth and vibrancy.
Screen resolution is the # of pixels on the screen.

Capacitive Resistive
Working  Made up of layers of glass which  Upper layer is made up of plastic and
have electric current between them. the bottom layer is made up of glass.
 When touched, the coordinates of  When the top layer is touched, a circuit
the touched area are determined is completed.

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and the request is performed.  Signals are sent to mp which determines
the coordinates of the touched area and
performs the request.
Advantages  Medium cost.  Very cheap.
 Good visibility.  Bare fingers, gloved fingers and stylus
 Multi touch compatibility. are source of input.
 Durable.
Disadvantages  Bare fingers are only source of  Poor visibility.
input.  No multi touch compatibility.
 Poor durability.

Virtual headsets:

 They receive video signals from the computer.

 The 2 feeds are shown on the screens on either side.
 Lenses are placed b/w the eyes which creates a 3D effect.
 Sensors are used to detect the movement of the head giving a realistic experience.
 Sound surround is also used which makes it seem that the sound is coming from a distance, sides
or back.
 These headsets allow one to access an inaccessible area such as nuclear power plant without
actually being there.
Sensors:

 Devices which measure physical properties.

 ADC (Analog to Digital converter) is used to when a device sends signals to the computer.
 DAC (Digital to Analog converter) is used when the computer is used to send signals to a device.

Sensors Uses
Temperature  Control heating system
 Monitor temperature in a greenhouse/
chemical process.
Moisture/Humidity  Control moisture levels in a greenhouse.
 Monitor dampness in industry such as
when painting a car.
Light  Switch lights on/off during night and day.
Infrared/ motion  Turn on windshield wipers on when it
rains.
 Detect intruder in burglar system.
Pressure  Detect intruders in a burglar system.
Sound  Pickup sounds in burglar system.
Gas  Monitor pollution in air/ water.
 Measure O2 / CO2 levels in the air.
pH  Monitor acidity, alkalinity of soil.
Magnetic field  Used in ABS in cars.
 Detects changes in cell phones.

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Working of ABS in cars:

 If one of the wheels of a car is rotating slowly, the mp checks the speed of the other 3 wheels.
 If they are rotating faster, then the mp reduces the braking force on the wheel.
 This is done so that the speed of rotation of all the wheels is constant.
 This is done several times to prevent the wheels from locking up when the brakes are suddenly
applied.
Difference between monitoring and controlling systems:

Past Papers:
Internal operation of a HDD [4]:

 Platters made up of glass and aluminium.

 Contain discs on a rotating spindle.
 Contains a concentric track and magnetic surfaces to store data.
 Consists of a read and write head.
 As the disc spins, the read and write head reads and writes data onto the magnetic surface of the
disc.

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The resistive touch screen has 2 layers with gap between the layers. When a finger touches the screen, the
top layer moves to touch the bottom layer; this creates a point of contact. The horizontal and vertical
position of this point is calculated.
Describe the purpose of RAM and ROM in a 3D printer. [4]
RAM stores the current instructions received from the computer. It also stores the data about the
components of the printer used in printing the current object.
ROM stores the basic boot up instructions and the OS of the printer.
Laser printer- The printer uses a laser beam and a rotating mirror to draw the contents of the page on the
photosensitive drum as electrostatic charge. The toner is attracted to this charge.
Describe the internal operation of a laser mouse.

 Laser shines onto a surface via a polished ring at the base.

 Light is reflected from the surface through the ring and detected by a sensor.
 Sensor captures the surface and then when the mouse is moved, detects changes in the surface
which is converted to x and y coordinates.
Internal operation of trackerball mouse.

 Ball touches horizontal and vertical rollers.

 When ball moves rollers move as well.
 As ball moves a beam of infrared light is broken creating pulses of light which help determine the
position of mouse.