Unit 3 Hardware And Software Pt. 1 Flashcards
Logic Gates types
Describe truth table of NOT,AND,OR,NAND,NOR,XOR gates
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
What is the stored program concept
- Stores instructions, programs and data in the memory,
- Instructions fetched and executed one after another one by one
Describe the fetch-execute cycle
- 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
Describe buses in Von Neumann
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
Components of Von Neumann:
ALU, ACC, PC, CIR, MAR, MDR
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
Interrupts and buffer
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
Describe how keyboard works
- 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
Describe how a 2D scanner works
- 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
Describe how a 3D scanner works
- 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
Describe how a barcode reader works
-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
Describe how a QR works
- 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
Describe how an interactive whiteboard works
- 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
Describe how a microphone works
- Input device
- Takes analogue sound and converts them into electrical signals
- So computer can understand and process it
Types of sensors
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
How is a sensor and microprocessor used to control a thing
- 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
Describe how an inkjet printer works
- 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
Describe how a laser printer works
- 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
Describe how a 3D printer works
- 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
Describe how a 3D cutter works
-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
Describe how a LCD works
− 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
Describe how a LED works and its benefits
− 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
Describe how a resistive touchscreen works
- 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
Describe how a capacitive touchscreen works
- 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
Describe how an actuator works
Operated by signals to cause a physical movement, controls the movement of a machine
Describe how a DLP/Projector works
Uses thousands of tiny mirrors that can move very quickly to create an image
Describe how a mouse works
− 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
