Unit 3 Hardware And Software Pt. 1

Question 1

Logic Gates types

Answer 1

Question 2

Describe truth table of NOT,AND,OR,NAND,NOR,XOR gates

Answer 2

Not- 1 input becomes 0 vice version
And- Only 1 and 1 gives 1 output
Or- Gives 1 when there is atleast 1 in inp
Nand- Gives 1 every time except 1 and 1
Nor- Only gives 1 when input 0 and 0
Xor- Gives 1 when only 1 input is 1

Question 3

What is the stored program concept

Answer 3

• Stores instructions, programs and data in the memory,

- Instructions fetched and executed one after another one by one

Question 4

Describe the fetch-execute cycle

Answer 4

• PC holds address of next instructions
• Address held in PC sent to MAR via address bus
• MAR goes to location in memory where instruction is stored
• Instruction sent to MDR via data bus
• Instruction then sent to CIR
• Control unit sends signal to manage process using control bus
• Value in PC incremented by 1
• Then instruction is decoded and executed

Question 5

Describe buses in Von Neumann

Answer 5

Address bus- carries signal relating to addresses between the processor and the memory; unidirectional

Data bus- can transfer data between the processes and memory and I/O devices; bi-directional

Control bus- carries signals relating to the control coordination of the fetch-execute cycle ; uni and bi-directional

Memory unit- Uses MAR and MDR, made up of partitions. Each has an address and contents. CPU only refers to main memory

Main memory- IAS, RAM, holds data/instructions currently in use. Directly accessed by CPU, Volatile memory

Question 6

Components of Von Neumann:

ALU, ACC, PC, CIR, MAR, MDR

Answer 6

ALU - Arithmetic and Logic Unit, allows for arithmetic calculations and logic operations to be carried out

ACC- Accumulator, register which acts as a temporary storage location for immediate result from the ALU and values from calculations

PC- Program counter, register used by CPU to hold address of next instruction to be executed

CIR- Current instruction register, holds instruction currently being executed or decoded

MAR- Memory address register, holds memory location of data that needs to be accessed

MDR- Memory data register, holds data content waiting to be written or read from location pointed by MAR

Question 7

Interrupts and buffer

Answer 7

Interrupt:

• To identify that the processor’s attention is required
• To stop the current process
• To allow multitasking
• To allow for efficient processing
• To allow for efficient use of hardware

Buffer:
-Region of memory used to temporarily store data while it’s being moved from one place to another

Examples of interrupts:

• Hardware issue, such as a printer paper jam
• Key press by the user, e.g. CTRL ALT DEL
• Software error

Question 8

Describe how keyboard works

Answer 8

• Circuit board present at base of keys
• When key is pressed that presses a switch
• When pressed the circuit is complete
• Location of key press is calculated
• Each character has an ASCII value
• Key press generates an interrupt

Question 9

Describe how a 2D scanner works

Answer 9

• A light is shone on the surface of the document
• Light source is automatically moved across the document
• Reflected light captured by mirror and lenses. Used to scan sheets of paper

Question 10

Describe how a 3D scanner works

Answer 10

• Works using laser or light source which is shone across the object
• The width,height,depth of object measured
• Model is replicated and created
• Used to scan patient bodies, scan an object to create copies

Question 11

Describe how a barcode reader works

Answer 11

-Input device
Scanned using a barcode reader
− Shines (red) laser/light
− Light is reflected back, white lines reflect light, black lines reflect less light
− Sensors/photoelectric cells detect the light
− Different reflections give different binary values
− Pattern is then converted to binary values
− Microprocessor interprets the data

Has to be bought separately
But
Quicker to scan than type, less human errors

Question 12

Describe how a QR works

Answer 12

• Illuminator/Light shone on code
• Black squares reflect different light to white
• Corner squares used for alignment
• Reflected light is focused on photosensitive cells or CCD
• Pattern converted to digital data
• Data sent to microprocessor

Question 13

Describe how an interactive whiteboard works

Answer 13

• Output device
• Fixed on walls
• User can calibrate the device to make sure sensors align with projected image
• Can use finger or pen to interact
• Where touch is performed, location is calculated and output is shown

Question 14

Describe how a microphone works

Answer 14

• Input device
• Takes analogue sound and converts them into electrical signals
• So computer can understand and process it

Question 15

Types of sensors

Answer 15

Light- Detect light, street lights

Temperature- detects temp, ovens

Pressure- detects pressure, collision

Magnetism- uses earth magnetic field

Humidity/Moisture- used in greenhouses

Acidity- pH of water, treatment of water

Motion- detects motion, burglar alarm

Question 16

How is a sensor and microprocessor used to control a thing

Answer 16

• Sensors take reading and data is sent to microprocessor
• Analogue signal from sensor converted into digital using analogue to digital converter (ADC)
• Microprocessor compares data against pre-set values
• If matched no action taken
• If not matched microprocessor sends signal and decreases or increases value accordingly
• Process is continuous and repeated

Question 17

Describe how an inkjet printer works

Answer 17

• Rollers used to move paper
• Nozzles sprays liquid ink onto paper
• Ink jet drops ink on paper
• Different coloured inks mixed to create ideal color
• May use thermal or piezoelectric tech

-Prints high quality, cheap to buy, no warmup time, more expensive per per, ink could smear

Question 18

Describe how a laser printer works

Answer 18

• Uses static electricity
• Uses powdered ink
• Rotating drum used to transfer image on paper
• Has negative charge
• Laser removed negative charge from areas and scans
• Toner transfers from drum to positively charged paper

-Prints high volume, cheaper cost per page, fast speed, expensive to buy, toner is expensive, has warm up time, heavy

Question 19

Describe how a 3D printer works

Answer 19

• Uses a moving print head
• Produces output using materials like plastic and resin
• Uses layer upon layer of material to create output
• Products can be customised but does have limitations to what can be made
• Uses piezoelectric or thermal technology

-Can create prototypes easily, prosthetic arms, dangerous objects could be created

Question 20

Describe how a 3D cutter works

Answer 20

-Design is created on the computer / software / CAD
-Material is loaded to cutter
-Different types of material can be used
-Uses lasers to cut material
that use infra-red
that produces extreme heat
that is focussed using a special lens
-Can work on both the x, y and z axis

Question 21

Describe how a LCD works

Answer 21

− Liquid crystal display
− The display is made of pixels arranged in a matrix
− Uses a flat panel display
− Backlit display with CCFLs/LEDs
− Uses light-modulating properties of liquid crystals
− Crystals can be turned between opaque and
transparent (to allow light to pass)
− Colours created using RGB

− Not good at low temp as crystals can become solid
− Low power consumption 
− Runs at cool temperature 
− Do not suffer image burn 
− Do not suffer flicker issues 
− Bright image/colours 
− High resolution image 
− Cheaper to purchase than e.g. LED screen

Question 22

Describe how a LED works and its benefits

Answer 22

− Light emitting diodes (technology)
− The display is made up of pixels that are arranged
together as a matrix
− Each is formed of three LEDs/filters
− Shades of colour are achieved by mixing red, blue and
green
− The screen can be back-lit/edge-lit

− Energy efficient // low power consumption
− Long lasting // longevity
− Focussed beam // less light strays from beam
− Brighter/vivid colours
− High resolution
− No flicker
− Display is thinner
− Mercury free technology // environmentally friendly
− Fewer pixel failure
− Increased viewing in sunlight

Question 23

Describe how a resistive touchscreen works

Answer 23

• Screen has 2 layers
• Needs pressure to be applied to create a circuit, top layer is pressed
• Calculation carried out where layers connect and output is produced accordingly
• It’s cheaper but easily damaged
• Used in GPS, printers, digital cameras

Question 24

Describe how a capacitive touchscreen works

Answer 24

• Electrical field spread across the screen
• Sensors located around the screen
• When finger touches screen, the charge is transferred to the user as it is affected by conductivity of the human body
• Coordinates of touch determination or calculated
• Used in smartphones, iPads
• Has multi-touch capabilities
• Can’t be used wearing gloves

Question 25

Describe how an actuator works

Answer 25

Operated by signals to cause a physical movement, controls the movement of a machine

Question 26

Describe how a DLP/Projector works

Answer 26

Uses thousands of tiny mirrors that can move very quickly to create an image

Question 27

Describe how a mouse works

Answer 27

− Uses rolling ball / optical sensor / laser to detect motion
− Movement echoed on screen /moves curser (on screen)
− Has scroll wheel / Buttons to allow data input