3. Hardware Flashcards
Define CPU
Central processing unit
responsible for the execution or processing of all the instructions and data in a computer
Define Von Neumann Architecture
a type of computer architecture which introduced the concept of the stored program in the 1940s
Define ALU
the component of the CPU that carries out all arithmetic and logical operations
Define ACC [Accumulator]
temporary general-purpose register that stores numerical values at any part of a given operation
Define MAR (memory address register)
a register that stores the address of the memory location currently being read from or written to
Define CIR [current instruction register ]
a register that stores the current instruction being decoded and executed
Define MDR [memory data register]
a register that stores data that has just been read from memory or data that is about to be written to memory
Define PC [Program couunter]
a register that stores the address where the next instruction to be read can be found
Define PC [Program couunter]
a register that stores the address where the next instruction to be read can be found
Define clock cycle
s temporary memory using static RAM to hold frequently used data/instructions by the CPU thereby increasing CPU performance. More generally, cache means any area of storage used to quickly access frequently-used data - other examples include web cache, database cache, DNS cache
Define register
a temporary component in the CPU which can be general or specific in its use; it holds data or instructions as part of the Fetch–Decode–Execute cycle
Define address
a label for a memory location used by the CPU to track data
Define memory location
a numbered place in memory where values can be stored
Define system bus
a connection between major components in a computer that can carry data, addresses or control signals
Define address bus
the system bus that carries the addresses throughout the computer system
Define data bus
the system bus that allows data to be carried from CPU to memory (and vice versa) or to and from input/ output devices
Define control bus
– the system bus that carries signals from control unit to all other computer components
Define unidirectional
can travel in one direction only
Define bidirectional
can travel in both directions;
Define over clocking
changing the clock speed of a system clock to a value higher than the factory/recommended setting
Define core
a unit on a CPU made up of an ALU, control unit and registers
Define dual core
A CPU containing 2 cores
Define Fetch-Execute-Decode
– a cycle in which instructions and data are fetched from memory, decoded and finally executed
Define BIOS
– a suite of programs on firmware that are used to perform the initialisation of a computer system during the boot-up process
Define opcode
– part of a machine code instruction that identifies what action the CPU has to perform
Define operand
part of a machine code instruction that identifies what data is to be used
Define instruction set
the complete set of machine code instructions used a particular microprocessor
Define embedded system
a combination of hardware and software designed to carry out a specific set of functions
Define barcode
a series of dark and light lines of varying thickness used to represent data; the code has to be scanned using laser or LED light source
Define keyfield
the field that uniquely identifies a record in a file
Define QR code
a matrix of dark and light squares which represent data
Define frame QR code
a type of QR code that includes a space for advertising
Define DAC
device that converts digital data into electric currents that can drive motors, actuators and relays
Define ADC
a device that converts analogue data (for example, data read from sensors) into a form understood by a computer
Define CCD
a light sensitive cell made up of millions of tiny sensors acting as photodiodes
Define virtual keyboard
an onscreen keyboard which uses the features of the touch screen to emulate a physical keyboard
Define touch screen
a screen that allows the user to select or manipulate a screen image using the touch of a finger or stylus; touch screens most frequently use capacitive, infra- red or resistive technology
Define RSI (repetitive strain injury)
pain felt in the muscles, nerves and tendons caused by a repetitive action (for example, excessive clicking of a mouse button over a period of time)
Define optical mouse
a pointing device that uses a red LED to track the movement of the device and then relays its coordinates to a computer
Define pointing device
an input device that allows the user to control the movement of an onscreen cursor or to allow onscreen selection by clicking a button on the device
Define CMOS
a chip that generates an electric current (or pulses) when light falls on its surface
Define DSP
a processor that calculates, for example, the coordinates of a pointing device based on the pulses of electricity received
Define optical character recognition
technology that can convert hard copy text or images into a digital format to be stored in a computer memory
Define CAD
software used to create drawings
Define CT scanner
technology that can create a 3D image of a solid object by slicing up the object into thin layers (tomography)
Define capacitive touch screen
a type of touch screen that uses the change in the screen’s capacitance (the ability to store an electrical charge) when it is touched by a finger or stylus
Define infra-red touch screen
a type of touch screen that uses infra-red beams and sensors to detect where the screen has been touched
Define resistive touch screen
a type of touch screen that uses two conductive layers which make contact where the screen has been touched
Define actuator
an output device that converts electrical energy into mechanical movement
Define DMD
a chip that uses millions of tiny mirrors on its surface to create a video display
Define thermal bubble
inkjet printer technology whereby tiny resistors create heat and form an ink bubble which is ejected onto paper in an inkjet printer
Define piezoelectric crystal
a crystal located in an ink reservoir within an inkjet printer; the crystal vibrates and forces ink out onto paper
Define direct 3D printing
a 3D printing technique in which the print head moves in the x, y and z directions
Location of a device on a network
IP address
Number that uniquely identifies device
MAC address
What does a control bus do?
Carries signals to synchronise the fetch-execute cycle
Directs the CPU
Can be unidirectional or bidirectional
What does a data bus do?
Carries data that is being processed
- Bidirectional
What does an address bus do?
Carries address locations of next item to be fetched
- Unidirectional
List the 5 different registers
MDR
MAR
PC
CIR
ACC
What is meant by the stored program concept?
Programs / instructions are stored in memory
Data is stored in memory
Instructions are fetched and executed one after another
Describe the role of the Program Counter
Holds the address …
- … of next / current instruction
What does a Program counter do?
Increments to point to the address of the next instruction to be fetched
What does an accumulator do (ACC)?
It holds the result of a calculation,
It is located in the Arithmetic Logic Unit (ALU)
What does a memory data register do (MDR)?
Temporary storage between the central processing unit (CPU) and primary memory
Describe the role of the ALU
− Carries out calculations
− Carries out logical operations
− Holds temporary / interim values during calculations
− …in a register called the accumulator (ACC)
5 examples of output devices
Inkjet printer
Laser printer
3D printer
Speaker
Projector
5 examples of input devices
Scanner
Microphone
Keyboard
Sensor
Barcode reader
How does a capacitive touchscreen work?
Made up of many layers of glass that act like a capacitor, creating electric fields between the glass plates in layers.
When the top glass layer is touched, the electric current changes, and the coordinates where the screen was touched is determined by a microprocessor
4 benefits of a capacitive touchscreen
Medium cost technology
Screen visibility is good even in strong sunlight
Multi-touch capacity
Very durable screen
2 drawbacks of a capacitive touchscreen
Only the use of bare fingers is permitted
- Special stylus is allowed
How does a heat-sensitive INFRA-RED touchscreen work?
Uses glass as the screen material
- Needs a warm object as an input
3 benefits of an INFRA-RED touchscreen
Allows multi-touch capacity
Good screen durability
Optical system allows bare fingers, gloved fingers or a stylus for input
3 drawbacks of an INFRA-RED touchscreen
Heat-sensitive system only allows the use of bare fingers for input
Very expensive
Good screen visibility in strong sunlight
How does an optical INFRA-RED touchscreen work?
Uses glass as the screen material
Sensors form a grid
The location of the touch is calculated using the coordinates in the grid
How does a touchscreen work (general)?
Sensors are located on the edge of the screen
Electric field all over the screen
When the finger touches the screen, the charge is transferred to the finger
Coordinates of the touch is calculated
How does a resistive touchscreen work?
Top layer: polyester
Bottom layer: glass
When the polyester layer is touched, the top layer and the bottom layer complete a circuit
Signals are interpreted by a microprocessor, the calculations determine the coordinates of where the screen was touched.
2 benefits of a resistive touchscreen
Cheap
- Can input with bare fingers, gloved fingers, or a stylus
3 drawbacks of a resistive touchscreen
Bad screen visibility in sunlight
Does not permit multi-touch capability
Bad screen durability
How does an inkjet printer work?
Data is stored in printer buffer
Uses liquid ink cartridges
Uses thermal bubble
Rollers used to move the paper
Uses a moving print head
Sprays ink onto the paper
Different colour inks are mixed to create required colors
How does a laser printer work?
Uses dry powder ink/toner
Data stored in printer buffer
Uses charged print drum
Uses static electric charges
Toner is fused to the paper
Positive charge is replaced by negative charge
How do 3D printers work?
Uses resin
Solid is built up in thin layers
Uses a moving print head
What does QR stand for?
Quick Response
Explain how the system scans the QR code and checks if a person can enter.
Laser shone on QR code
Black squares reflect different light to white squares
Pattern is converted from analogue to digital by an ADC
The data is sent to a microprocessor
There is a database of valid QR codes
The data is compared to stored values
If data matches, entry is allowed
If data does not match, entry is no allowed
How does a barcode reader work?
Shines light at the barcode and light is reflected back
The black bars in the barcode reflect less light than the white bars
Sensors read the data
The pattern is converted from analogue to digital data by the ADC
Microprocessor interprets data
Advantages of using barcodes to the management
Can check stock levels
Can check if there is stock in a different location
When new stock items arrive, the stock levels are automatically updated in the database
Can check price
2 examples of primary storage
RAM (Random access memory) and ROM (Read-only memory)
2 examples of secondary storage
SSD (Solid-state drive) and HDD (Hard disk drive)
3 features of ROM
Non-volatile
Cannot be changed
Used to store the start-up instructions when the computer is first switched on
4 features of RAM
Volatile
Used to store data and files
Can be changed
Never runs out of memory, it just gets slower and slower
Drawbacks of HDD
Very slow compared to RAM
Large number of head movement needed
Expensive to change technology
Advantages of HDD
Cheaper for large amounts of data
- Greater longevity for read/write functions
Advantages of SSD
More reliable
Light
Portable
Lower power consumption
Faster than HDD
Example of SSD
USB flash drive
What does MIDI stand for?
Musical Instrument Digital Interface
What is MIDI?
− Musical Instrument Digital Interface (file)
− Stores a set of commands/instructions (for how the sound should be played)
− Does not store the actual sounds
− Data in the file has been recorded using digital instruments // produced by synthesizer
− Specifies pitch of the note // specifies the note to be played
− Specifies when each note plays and stops playing // Specifies key on/off
− Specifies duration of the note
− Specifies volume of the note
− Specifies the tempo
− Specifies the type of instrument
− Individual notes can be edited
What is MP3?
− MP3 is a format for digital audio
− MP3 is an actual recording of the sound
− MP3 is a (lossy) compression format
− Recorded using a microphone
What format does MP3 use?
Lossy compression format
Is a thermometer a sensor+why
No, it is a tube filled with alcohol or mercury that can be read by a human eye in comparison to a scale, computers cannot see the level so it needs something else.
Whast sensor do you use to measure motion
Infra-red
What sensor do you use to measure temperature
Temperature sensor
Where would you use a pH sensor
In a pool
Where is an acceleromenter used
In a car
What are sensors
Input decives that can read or measure physical properties from their surroundings.
Explain real data+1 eg,
Real data is anologue in nature, meaning that there are infinite no of values and the data requires interpretation/best judgemnent from user
Computers cannot make sense of real data
Thermometer
What is an ADC
An Anologue Digital Converter
Takes real life data/physical quantities and converts them to digital format/discrete digital values.
What is a DAC+eg of when they are used
Digital to anologue converter
When a computer is used to control devices eg.valve
Actuators are used
What is an actuator
A device thatelps achieve physical movements by converting energy to mechanical force
What is feedback
When the output readings of a sensor are recieved by the microproccessor and may impact the next input to bring the system within the desired parimetres.
What are the 2 types of applications for sensors
Monitoring and control
Explain monitoring sensor use+eg.
If the new data recieved is outside the acceptable range,a warning message/alarm appears
The microprocessor/computer has no effect on what is being monitored, they simply observe and notify
Pollution in river
Explain sensor applications:control
Eg.
If the new data recieved is outside the acceptable range, the computer/microprocessor sends signals to control aspects of the system/device. Output from the system affects the next set of inputs (feedback loop)
Chemical process control(maitnaining pH)
Where are magnetic field sensors used
Anti-lock braking systems
What does the CPU consist of
CU-control unit
ALU- arithmetic and logic unit
Registers and buses
What is a CPU
Central processing unit
Responsible for execution/processing of all instructions and data in s computer
Often installed as an integrated circuit on a microchip
What did John van Neumann do
What features did it have
Developed a stored program computer in the 1940’s
Concept of CPU
CPU could access RAM directly
Memory could store programs and data
Stored programs were made up of data in sequential order
What are the main components of the CPU
ALU-arithmetic and logic unit
CU-control unit
Registers
What does the ALU in the CPU do
Allows arithmetic, logic and or operations to be carried out whilst a program is being run
There can be more than one ALU to carry out specific functions
What does the CU in the CPU do
Reads instruction from memory/controls flow of infor
Address of location where instruction is found is stored in the PC (program counter)
Generates command signals along control bus
System clock is used to produce timing signals for^(without system would crash)
How is the instruction from the PC interpreted
Fetch-decode-execute cycle
Where + how does the CU access its data and programs
In the RAM/IAS(immediate access store)
The CPU takes data and programs held in a backing store and temporarily puts them into RAM
This leads to faster operations
What are registers function in CPU
General or special purpose eg.
ACC-actuator(carries out ALU+temporarily stores data)
PC-program counter(stores address where next instruction is found)
MAR-memory access register(stores address of memory currently being read/written from)
Logic Gates
OR )>
AND |)
NOT |>º
NOR )>º
NAND |)º
XOR ) )>
XNOR ) )>º
Truth Tables
Truth tables are compiled in numerical order
OR:
A OFF , B OFF = 0
A OFF , B ON = 1
A ON , B OFF = 1
A ON , B ON = 1
AND:
A OFF , B OFF = 0
A OFF , B ON = 0
A ON , B OFF = 0
A ON , B ON = 1
NOT:
A OFF = 1
A ON = 0
NOR:
A OFF , B OFF = 1
A OFF , B ON = 0
A ON , B OFF = 0
A ON , B ON = 0
NAND:
A OFF , B OFF = 1
A OFF , B ON = 1
A ON , B OFF = 1
A ON , B ON = 0
XOR:
A OFF , B OFF = 0
A OFF , B ON = 1
A ON , B OFF = 1
A ON , B ON = 0
Logic Statements
Writing a logic statement, steps:
X (or other) =
final logic gate in the middle
brackets on either side of gate in the middle
logic gate in middle of either bracket for both sides and continue working backwards
Logic circuits
From information or logic statement, work from middle gate and place last and continue working from middle till done.
Computer Architecture
Stored program concept (Von Neumann Architecture)
single processor in computer system
processor uses sequential fetch-execute cycle
data (files) and instructions (software) both stored in same memory (RAM)
Prior to this if a computer wanted to carry out another task it would have to be physically rewired
Processor Cycle
Main stages of the processor’s cycle
Fetch - the instruction
Decode - the instruction
Execute - the instruction
Parts of a processor
Memory Unit:
temporary storage areas for data and instructions
inside the processor (not within RAM)
Arithmetic-Logic Unit (ALU):
carries out mathematical equations on data
evaluates relational comparisons
inside the ALU is a general-purpose register called the accumulator (data needs to be placed in the accumulator for calculations to be carried out by the ALU)
Control unit:
co-ordinates what and where data goes when it enters or leaves the processor
it also controls the interactions between the different parts of the processor (e.g. the registers)
IAS/Immediate Access Memory (Cache memory):
A processor also has built-in cache memory. This is super-fast memory (much faster than RAM) that is stored within the processor.
Parts of Processor (Image structure)
Processor image (3 images)
Refer to IG Computer Science OneNote for answer
OneNote > Content Library > Unit 3 > Parts of a Processor
What is a register
A temporary memory location within the processor.
Registers store data and instructions whilst they are being processed.
Registers are also used to move data and instructions into and around the different parts of the CPU.
Special types of Registers
MAR - memory address register
Contains the location in RAM of the current instruction being processed
MDR - memory data register
Contains the contents (values, instruction) returned from RAM
CIR - current instruction register
Contains a copy of the contents of the MDR
Responsible for decoding the instruction
PC - program counter
The location (memory address) in RAM of the next instruction to be fetched
General Purpose Register
ACC (accumulator) - stored in ALU
Keeps track of data that needs to be accessed over a period of time during processing
Buses
Buses are wires used to transmit data within the processor and on the motherboard.
Three types of buses:
Address bus
- used by PC and MAR to transmit locations in RAM (i.e. addresses)
Control bus
- used by the PC and the MDR to send instructions
Data Bus
- used to carry data between RAM and the MDR, and between the MDR and the CIR
Stages in the fetch-execute cycle
Fetch execute cycle steps
PC has address of next instruction
PC copied to the MAR
Lookup MAR and get contents. Copy contents into the MDR
Copy MDR contents into the CIR
PC is then incremented by 1
The instruction is decoded and then executed
Repeat
Input devices - 2D scanners
How a 2D scanner works:
How a (_____) works:
OCR:
An input device digitised by a scanning device such as flatbed or barcode scanner.
How a 2D scanner works:
Scanner shines a light beam onto document.
Scanner detects level of reflected light from positions on the document.
Light intensity is converted by software for each pixel position into a combination of 0s and 1s by sensing different intensities of light and dark from the document.
How a flatbed works:
Place document - raise cover, put document on panel and close
Very bright light - (xenon lamp)
Scan head - moves across the document and image is created and sent to a lens using mirrors
Charge Couple Device - focused image falls on CDD, IC’s etched into silicon and software produces digital image
OCR Optical character recognition:
OCR alongside 2D scanner used in airport for passport to face identification
eg.
Distance between the eyes
Width of the nose
Shape of the cheek bones
Length of the jaw line
Shape of the eyebrows
Input devices - Linear Barcodes
Linear Barcodes are 1D and the most commonly used
Steps:
Infra-red laser light shines onto linear barcode.
Light reflected back into the moving mirrors/prism
The barcode reader’s charge-coupled device (CCD) measures the amount of reflected light input.
Light measurement is converted into an electrical charge (1 or 0).
Data from the bar code is sent to the computer’s processor in binary form.
Input devices - QR Codes
Quick response codes are faster to read and have a greater storage capacity than UPC linear barcodes.
Scanned digitally by phone’s image sensor then interpreted by microprocessor.
Input devices - Keyboards
Keyboard works using plungers at the bottom of each key which when pressed pushes 2 electrical contains completing a circuit (key matrix).
Key matrix (circuits) stored in ROM
Input devices - Mouses
Trackerball Mouse:
- Similar to the concept of the original mouse but upside down. The movement of the ball in the socket contains sensors. The data from the sensors processed by a software determines the movement of the pointer.
Optical Mouse:
- A red LED bounces light off the surface onto a CMOS sensor which sends each image to the DSP for processing. The DSP detects if the mouse has moved, at what distance and at what speed.
Input devices - Microphones
All microphones need to input a varying pressure wave and then convert this to an electrical reading.
Sound vibration hits a diaphragm.
Movement of the diaphragm causes a coil to move.
Movement of the coil induces a current through the electromagnetic effect.
The electrical current is digitised (ADC - analogue-digital converter)
The digital content is played back using software.
Sensors - Light, Temperature, Pressure, Motion, Gas, pH, thermal, moisture, humidity
Light:
Light Sensors are photoelectric devices that convert light energy (photons) into an electrical (electrons) signal
eg. barcode scanner, automatic lights as it gets dark
Temperature:
A temperature sensor is a device, typically, a thermocouple or RTD, that provides for temperature measurement through an electrical signal.
eg. thermometer
Pressure:
A Pressure sensor measures the amount of force exerted.
eg. old-style electric doors, pressure inside gas canisters
What are registers function in CPU
General or special purpose eg.
ACC-actuator(carries out ALU+temporarily stores data)
PC-program counter(stores address where next instruction is found)
MAR-memory access register(stores address of memory currently being read/written from)
Primary/Main Memory/Storage
All computers must use Primary storage and it is directly accessible by the processor because it is connected directly to the motherboard.
- RAM random access memory
RAM is volatile and directly connected to the CPU.
RAM
RAM stores data and instructions that are currently open and running. If a file or program is not open, it will not be in RAM.
RAM contains parts of the operating system that are currently in use. Contents stored in RAM are directly accessible to the processor. When you load a stored file it is first loaded into RAM before any changes made to the file are processed by the CPU.
RAM is volatile so when power to the computer system is lost so are the contents of RAM.
Storage capacity is in GB and has read and write ability.
Its contents change every time we use a computer.
ROM
ROM stores your computer system’s BIOS and bootstrap loader.
Basic Input Output System (BIOS)
Most do not need to access the BIOS on a regular basis, if at all. The BIOS allows us to change things like the bootable drive.
Bootstrap loader
When you first turn on (‘boot’) your computer, the operating system has not yet loaded.
Your computer performs a self check of its hardware. It makes sure that it recognises it has RAM and a bootable drive of some sort.
ROM is non-volatile memory between 4-8 MB storage
Secondary Memory/Storage
Types
Use in a laptop or computer
What it is
Magnetic/Solid state/ off-line
A laptop or desk top computer either has an (HDD) or an (SSD) as its main secondary memory/storage device.
Secondary storage devices are not directly accessed via the processor. Their contents are first be loaded into RAM before being transferred to the CPU for processing.
How HDDs work
An HDD platter is magnetic
the film stores data (bits)
bits are written to using the magnetic read/write head
the positive or negative charge (polarity) is different for a 1 and 0
SSD
SSDs are non-volatile storage devices
No moving parts
Uses flashing light to store data on chips
Solid state external device
Large storage capacity
HDD vs SSD
HDD:
cheaper
longer lifespan
larger storage capacity
SDD:
uses less power
skinny compact
no delay when reading or writing data
less heat produced
quieter
more durable (harder to break)
Secondary storage device Types and examples
Magnetic:
Magnetic tape
Floppy discs/drives
HDD
Optical:
CDs
DVDs
Blu-ray
DVD-RAM
Solid state:
SSDs
USB Flash memory/memory sticks
SD cards
Offline storage
Types and examples
Offline storage is external to the computer system and can be taken away from the computer.
Magnetic:
- external HDD
Optical:
CD
DVD
Blu-ray
Solid state:
external SSD
memory stick (not USB on it’s own)
SD cards
How a CD works
Data is stored on the CD on a single spiral track in pits (0s) and lands (1s).
The CD drive spins the CD at a constant speed.
A red laser shines on the CD’s surface.
Light is reflected from the disc from the pits and lands, which is how binary data is read from the CD.
Primary storage vs. Secondary Storage
Types
Volatility
Contents
Placement
Read/Write access speeds
Relationship to CPU
Primary Storage:
RAM - volatile, ROM - non-volatile
RAM - currently running programs and files, ROM - BIOS and bootstrap loader (start-up instructions)
Internal placement
RAM - plugged onto motherboard
ROM - soldered onto motherboard
Faster than secondary storage
Directly accessible by the processor (CPU)
Data and instructions must be in RAM before being sent to the CPU for processing
CPU loads the operating system when the bootstrap loader in ROM runs when the computer is turned on
Secondary Storage:
HDD, SSD
Both are non-volatile
Both - stores files and programs for long-term storage
Internal and external options
Inside computer case, attached to motherboard via cable
Portable HDD or SSD, connected via USB port
Slower than primary storage
Contents are not directly accessible by the processor (CPU)
Data and instructions on HDD and SSD (internal and external) is loaded into RAM first
Blu-ray vs. DVD
DVD red laser
Blu-ray blue laser and more storage
DVD vs. DVD-RAM
DVD read only and one spiral track
DVD-RAM read and write (at same time too) and multiple concentric tracks
Flash memory vs. CD-RWs
Type of offline storage media
How data is read/written
Read/write access speed
Hardware
Flash memory:
solid state
transistors/logic gates
faster than CD-RW because no moving parts
plugs directly into computer via USB port
CD-RW:
optical
red laser
slower than flash memory
requires a separate CD drive to read or write data
Output devices - Inkjet printer
They operate by heating the ink as it flows through a set of tiny nozzles. The heating process causes a small droplet of ink to form. This is then released as a single dot which forms part of a letter or image.
Either thermal uses heating element to make air bubble
or piezoelectric crystal to vibrate
adv. Cheap, compact, faster than dot matrix, quiet
disadv. colour is slow, wet ink can smudge
Output devices - Laser printer
Laser printers used the same technology as photocopiers.
(Image refer to laser printer image in OneNote)
Laser beam and rotating mirror used to draw image of page on drum.
Image converted on drum into electrostatic charge, this attracts and holds toner.
Charged paper rolls against the drum.
Charge pulls the toner away from drum and onto paper.
Heat fuses the toner to the paper.
The electrical charge is removed from the drum and the excess toner is collected.
NB - for multiple colours, multiple drums
Output devices - Dot matrix printer
Comparatively noisy and low quality but cheap to run and used when carbon copies or duplicates are needed. Useful in dirty environments such as a garage because they are very sturdy.
Output devices - 3D printer
3D printers use an additive printing process, using melted layers of plastic (filament) to create 3D objects.
A 3D printer builds up an object from adding more and more layers of material usually PLA.
Output devices - Speaker
A loudspeaker takes an electrical signal and translates it into physical vibrations to create sound waves. The speaker is carrying out the exact reversal of what is done by a microphone.
Main components are a voice coil, diaphragm and magnetic.
Output devices - Flat panel display screen (LCD & LED)
LCD Technology
LED Technology
LCD v LED
Liquid Crystal Display (LCD)
Uses light modulating properties of liquid crystals
1. The screen comprises individual red, green and blue (RGB) pixels that are organised into small blocks.
2. Each ‘block’ is made of liquid crystals (hence the name, LCD!)
3. When the electric current being sent to the block of liquid crystals changes it causes the pixels to also change by turning solid or transparent.
Light-Emitting Diodes (LED) Display
- Uses an array of light-emitting diodes as pixels
LEDs use the same technology as LCDs to create an image
LCD advantages:
less power
low manufacturing cost
LED advantages:
no added light sources needed
works well in very hot or cold temps
fast
doesn’t need an AC drive
Output devices - Touch screens
(Refer to OneNote for images)
Capacitive:
Made up of an insulating layer of glass that is coated with transparent conductive material. When an area of the screen is touched the voltage drops there. The processor uses the change in the electrical field to calculate where the screen was touched. (refer to OneNote for image)
Resistive:
Made up of two separate layers, bottom glass top plastic. When touched the two layers meet and this sends a signal to the processor, which uses the coordinates of the screen to calculate where it was touched.
Infra-red:
Screen is made of glass and requires human input for touch, if touched in multiple places the location can’t be determined. Works with matrix of IR beams like lasers in spy movie.
Output devices - Projectors
Liquid Crystal Display (LCD) projectors:
sharper/better image quality
Quieter
pixels are more visible
uses less power and runs cooler than a DLP projector
projects light through three prisms (RGB)
three lights (RGB) merge when they pass through a fourth prism to display an image onto a large screen
Lamp > separation prism > colour filter > combining prism > lens = image
Digital Light Projectors (DLP) :
lighter, more portable
produces ‘blacker blacks’
often more expensive than regular LCD projectors
uses a thousands of micro mirrors (built onto on integrated circuit (chip)) to project an image onto a large screen
Lamp > condensing lens > colour filter > shaping lens > DMD > lens = image
Operating systems
An operating system is a collection of programs that form the basis of the main system software found in a computer system. An operating system provides a platform for application software to be installed.
Interrupts
An interrupt is an electronic signal from hardware or software that requests the processor’s attention.
An operating system contains a program called an interrupt handler. The role of the interrupt handler is to prioritise the interrupt signals as it receives them and places them in a queue to be handled.
Interrupts can be hard or software based, are handled by the operating system, allow a computer to multitask, does not work out priority and a computer cannot function without interrupts.
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Interrupts are signals sent to the CPU by external devices to indicate that an event needs immediate attention
They tell the CPU to stop what it is currently doing and give priority to the interrupt
Hardware interrupts are generated by hardware devices eg. printer out of paper
Software interrupts generated by programs
eg. divide by zero
Software
Software Categories
Software types
Categories:
System software, Application software
System software:
Programs that are needed to run the computer eg. windows
Application software:
Programs that are needed to perform tasks for the user
Free software, freeware, shareware:
Most commercial software has to be paid for
Using an unlicensed copy of software is a copyright infringement and is illegal
Some software is free of charge and allows users to study, modify and distribute it
Free software
Free software is software that comes with permission to use, copy and distribute it with modification either gratis or for a fee
Open source software
Open source software is free of charge and the source code is given to a user to use in any way they like
Freeware
Freeware may be used without payment it may permit redistribution but not modification as the source code is not available.
Examples:
Google chrome
Skype
Adobe reader
Shareware
A software that is initially free on a trial basis
The software is copyright and after trial must be paid for, the source code is not available and it can not be modified but is often encouraged to be made copies of and shared to help distribute it.
Operating Systems
System software types
Examples of OS
Definition and function
System software:
Operating systems
Utility programs
Program translators
Examples:
IOS
Android
OS X
Windows
Google chrome
Linux
Definition and function:
Software that manages a computer’s hardware and provides a user interface
Also provides security
User interface
mini def
Types x 6
Without user interface we would communicate in binary
Types:
GUI , graphical user interface; most commonly associated
Menu-driven interface; music players and ATM machines
CLI, command line interface; all user commands types in as text and no graphics, uses less space on disk and RAM
Voice activated
Real-time
Windows; WIMP - Windows, Icons, Menus and Pointers; user can click on icons using a pointer or cursor and right click to display a menu
How computers handle Memory Management
Data used by the computer is copied into main memory
The operating systems keeps a record of where each program and its data are located
It must not overwrite pre-existing programs
Multi-Tasking
When running multiple programs on a computer,
the programs in the background running are taking turns to get processor time to execute instructions
The OS Manages how the programs share the processor
Task manager
Peripheral management
Peripherals are all the devices outside of the CPU, input/output devices and secondary storage, access speed of these is relatively slow
Print buffer
Status of each job on a printer screen displaying whether it is printing or waiting to print
Storage device and disk file management
who manages and what they do
def
OS manages:
Copying files from disk to main memory
Copying data files back to secondary storage
Hard disk in computer is a storage peripheral:
OS manages where on disk files are written, keep track of their location to be fetched, making sure no file overwrites another file
Logic Gates types
OR )>
AND |)
NOT |>º
NOR )>º
NAND |)º
XOR ) )>
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
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
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
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 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
Describe Primary Storage
− Memory that is directly accessed by the CPU
− An example is RAM / ROM
− RAM stores programs and data that are currently in use and ROM stores boot-up instructions
− RAM is volatile and ROM is non volatile
− RAM typically has more storage than ROM
− Volatile memory means data is lost if device is powered off, non-volatile is when data remains even after device is powered off.
Describe Secondary Storage
− Storage that is not directly accessed by the CPU
− An example is HDD / SSD
− Stores data / files that can be accessed at a later stage
− Non volatile
Describe why is SSD better than HDD and vice versa
SSD better than HDD:
− Faster read/write operation
− Less latency
− Produces less heat // needs less cooling
− Less susceptible to interference/magnets
− Less power consumption
HDD better than SSD
−Cheaper
− Infinite amount of read/write cycles
Describe how a SSD works
SSD
− Flash storage
− Uses transistors and controls gates
− Can be NAND/NOR technology
− Stores data by flashing it onto the silicon chips
− Controlling using the flow of electrons through transistors/chips/gates
− The electric current reaches the control gate and flows through to the floating gate to be stored
− When data is stored the transistor is converted from 1 to 0 / 0 to 1
− Some use EEPROM technology
Describe how a HDD works and benefits
− It has platters
− Platters/disk divided into tracks
− Platter/disk is spun
− Has a read/write arm that moves across storage media
− Read/writes data using electromagnets
− Uses magnetic fields to control magnetic dots of data
− Magnetic field determines binary value
Benefits:
− Has more longevity than solid state storage
− Has more read/write cycles than solid state storage
− Cheaper per unit of data
− Trusted technology used for many year
Describe how off-line storage works
How its read
− Red laser is used, laser beam shone onto disk
− Disc is rotated on a constant speed to be read
− Surface is covered in track
− Data is represented on the surface using pits and lands
− Pits represent binary valves
− Pits reflect light back differently
How data is written
− Laser beam is used
− Laser makes indentations on the surface of the disc
− Data is written in spiral track
− Pits and lands represent binary values
− It is non-volatile
− Can be easily disconnected from the computer or inserted
− It is not directly accessed by the CPU
− Suitable example e.g. CD, DVD, USB flash memory
− Portable, small
− Expensive to buy per GB
Examples of optical, solid state, magnetic storages
Optical- CD, DVD, Blu-ray
Solid state- USB flash drive (important to mention flash drive) , SD cards
Magnetic- HDD
Difference between DVD and Blu-ray
− DVD uses red laser/light whereas blu-ray uses blue/violet laser/light
− DVD has a smaller (storage) capacity // Blu-ray has a larger (storage) capacity
− DVD has two layers (of polycarbonate) whereas Blu-ray disks have a single layer (of polycarbonate)
− DVD has a slower transfer rate (of approximately 10 mbps) // Blu-ray has a faster transfer rate (approximately 36 mbps)
Describe how an infra-red screen detects a users touch
Infra red rays are sent across the screen from the edges
Sensors are around the edges and capture beams
Infra red is broken by a finger blocking it
Calculation is made to locate the touch based on where the beam was broken
what is an IP address
location of a device on a network
what is a MAC address
number that uniquely identifies a device
Ram types (2)
DRAM
- SRAM
DRAM(8)
Constructed of tiny capacitors that leak electricity
Requires a recharge every few milliseconds to maintain its data
Inexpensive
Slower SRAM
Can store many bits per chip
Uses less power
Generates less heat
Used for main memory
SRAM(8)
Constructed of circuits
Hold its contents as long as power is available
Expensive
Faster than DRAM
Can store many pits per chip
Uses more power
Generates more heat
Used for cache
ROM(4)
Non-volatile memory chip
Primary memory
In a microprocessor holds the BIOS
Can’t be written to
Types of ROM(3)
PROM (Programmable read-only memory) – It can be programmed by user. Once programmed, the data and instructions in it cannot be changed.
EPROM (Erasable Programmable read only memory) – It can be reprogrammed. To erase data from it, expose it to ultra violet light. To reprogram it, erase all the previous data.
EEPROM (Electrically erasable programmable read only memory) – The data can be erased by applying electric field, no need of ultra violet light. We can erase only portions of the chip.
EEPROM(4)
NAND
More expensive
Faster read
Erase singular byte
SSD (4)
NOR chips
Less expensive
Slower read
Erase blocks of bytes
Cache (5)
Cache holds the information from the RAM that is most actively used, and accessed most frequently.
The computer system will run faster as the slower main memory will need to be accessed less frequently.
When the processor needs to read from the main memory, it first checks if a copy of the data exists in the cache.
If the data to be read do not exist in the cache, the data are first copied to the cache and then used.
When the processor needs to write to the main memory it does so through cache memory.
Remote control car example
-RAM
Contains instructions currently in use
-ROM
Contains the startup/bootstrap program
-SSD
Stores program data to operate the car
Types of secondary storage (2)
HDD
- SSD
HDD(6)
Uses platters
Platters divided into tracks
Platter is spun
Read write arm moves over platter
Magnetic fields control magnetic dots of data
Magnetic field determine binary value
SSD(2)
Non-volatile memory
- Uses NAND flash memory
Why SSD>HDD(6)
No moving parts (more reliable in a portable device)
Use less power
Smaller (good for portable devices)
Faster data access
Run cooler
Run quieter
Why HDD>SSD for webservers
Cheaper for large amounts of data
Greater longevity for read/write functions
Don’t need faster speed of SSD
Expensive to change technology
Optical storage examples(3)
CD
DVD
Blu Ray
DVD(3)
Uses 1 spiral
Red laser used to read/write
Dual layer technology
DVD-RAM(2)
Uses concentric tracks
- Allows read/write operations at same time
DVD-R Vs DVD-RAM(4)
DVD-R one spiral track DVD-RAM several concentric tracks
DVD-RAM can be written to and read at same time;DVD only allows read
DVD-R only allows read; DVD-RAM allows read and write
DVD-RAM can have direct access because of concentric tracks
Blu Ray (2)
Uses blue laser
- Uses single1.1mm polycarbonate disc
Blu Ray vs DVD
Larger Capacity
Blue laser rather than red laser
Single polycarbonate layer not two layers
Tape vs SSD in severs (5)
Greater longevity – more read and writes
Speed is sufficient
Cheaper per unit of data – better value
No portability requirement
Trusted technology
two more types of portable storage
portable HD
USB flash drive
what does an operating system do? (6)
loads software
Manages hardware
Manages error handling
Manages user accounts
Allows multitasking
Provides an interface
how does interrupt work (4)
A signal sent to the processor
Requests processor time
Processor stops to service interrupt
Interrupts have different priorities
name 3 devices that use interrupt
Printer
Keyboard
Mouse
name the 3 buses
Control bus
Address bus
Data bus
what does a Control bus do (3)
Carries signals
Directs the CPU
Can be unidirectional or bidirectional
what does an Address bus (2)
Carries address locations of next item to be fetched
- Data travels one way ( unidirectional)
what does a Data bus(2)
Carries data that is being processed
- Data travels in both directions (bi-directional)
name the 5 registers used
PC; Program Counter
MAR; Memory address register
MDR; Memory data register
CIR; Current instruction register
ACC; Accumulator
role of the control unit (4)
Controls operation of memory, processor and input/output
Fetches each instruction in turn
Interprets instructions
Sends signals to other components telling them what to do
role of the ALU (arithmetic logic unit) (3)
Carries out calculations
Carries out logic operations
Holds values during calculations in a register called an accumulator (ACC)
explain the stored program concept
Programs / instructions are stored in memory
Data is stored in memory
Instructions are fetched and executed one after another
Input Device =
A device that allows data to be entered into a system
Output Device=
A device that allows the user to see/hear data
explain how execute fetch system operates (6)
PC has address of next instruction to fetch
PC copied to MAR via address bus
Instruction copied from memory to MDR
Instruction copied from MDR to the CIR
Value in PC incremented to point at next instruction to fetch
Address of instruction placed in MAR
Instruction decoded and executed
how does a 2D Scanner work (5)
Paper placed on a glass panel
Bright light illuminates the document (modern scanners use a xenon light)
Scan head moves across the document
Lens focuses on the document image
Scanned image turned into electric form by the CCD
application of 2D scanner (2)
At airports to read passports
- OCR software used to read text
application of 3D scanner (2)
CT Scanners
- MRI Scanners
how does a barcode Scanner work (6)
Red laser shone at barcode
Light is reflected back
Sensors detect the light back
Pattern converted to digital
Microprocessor interprets the data
Each digit made up of 2 dark and 2 white lines
advantage of using a barcode scanner to the company (3)
Easy to change prices on stock items
No need to price every item on the shelf
Allow for automatic stock control
advantage of using a barcode scanner to the customers (3)
Faster checkout
Reduces errors
Itemized bills
how does a QR code Scanner work (8)
QR Code scanned by camera
Light reflected back
Black squares reflect less than white squares
Three large squares used to define alignment
Squares data is decoded – each square has a binary value
Processed by an app
Links to website or document
QR code can be saved and used again
QR Code v Barcode (4)
Barcode 1D QR is 2D
QR code can contain more data
QR code can be read from any angle
QR codes faster to scan than bar codes
Benefits Concept Keyboard (3)
Fewer typing errors because one button is pressed to order an item
Speeds up time to order because fewer buttons pressed
May require less training
how does a microphone work (2)
A diaphragm vibrates producing an electric signal
- Signal goes to a sound card and is converted into digital values
how does Voice recognition system work (4)
Users voice converted into digital signal
Spoken words produce a digital pattern
Software compares wave pattern to patterns stored in memory
If they match person is identified
speech recognition=
Spoken words recognized and shown on screen
problems of speech recognition (2)
The software needs to be trained
- Some dialects and accents can cause problems
application of speech recognition (2)
Cars
- Siri
how does resistive touch screen work? (2)
Uses multiple layers of material that transmit electric current
When top layer is touched into the lower layer current changes and location is found
advantage of resistive touch screen (2)
Cheap to make
- Can use when wearing a glove
how does Capacitive touch screen work (4)
Conductive layer
Current flows from 4 corners – electric field created
Sensors monitor field
When screen is touched charge transferred to finger - current changes and location is calculated
disadvantage of resistive touch screen (3)
Poor in sunlight
Easily scratched
Doesn’t allow multi touch
advantage of capacitive touch screen (3)
Good in sunlight
Durable
Allows multi touch
disadvantage of capacitive touch screen (2)
Screen can crack on impact
- Can’t use while wearing gloves
how does infra red work? (2)
- Invisible grid of infra-red beams on screen
- When screen is touched beam is broken and location is calculated
advantage of infra red (3)
Durable
Allows multi touch
Can use with gloves
disadvantage of infra red (3)
Expensive to make
Screen can crack on impact
Sensitive to dirt
types of sensors (6)
- Temperature
Aircon, central heating - Motion
Detects if an infra-red beam has been broken and sends a signal to the microprocessor - Pressure
Detects a change in pressure and receives current if a circuit is created sending a signal to the microprocessor - pH
- Light
- Magnetic fields
7.Anti-lock brakes on a car
examples of Monitoring Applications (3)
Burglar Alarm
Street Lights
ABS Brakes
Control Systems Process (7)
Sensor detects input (Name the sensor)
Analogue data converted to digital
Signal sent to microprocessor
Microprocessor compares signal to stored value
If value outside range signal sent to device
Actuator used to operate device
Process is in a continuous loop
Printers (2)
Interrupt - Signal sent to computer about no paper
- Buffer – Area of memory used to temporarily store data being sent to the printer
Types of Printer (3)
Laser
Inkjet
3D
Inkjet (8)
Used for low quantities of documents
Used for photographs
- Uses liquid ink cartridges
- Uses thermal bubble
- Rollers used to move the paper
- Uses a moving print head
- Sprays ink onto the paper
- Different colour inks are mixed to create required colours
Laser (5)
Used for high volume quality output
User toner cartridges
Uses charged print drum
Uses static electric charges
Toner is fused to the paper
3D(4)
Used to make physical model from blueprint
Used to create physical model from CAD
Uses resin
Solid is built up in thin layers
Uses inkjet technology with a moving head
Binder 3D printing (3)
Similar to direct but uses two passes
1st pass sprays dry powder
2nd pass sprays a binder (type of glue)
2D & 3D Cutters(1)
-Very complex designs can be made as the cutters are controlled by computers
Speakers & Headphones(3)
Sound produced by passing digital data through a digital to analogue converter (DAC) then through an amplifier
Sound produced by voltage differences vibrating a cone
Rate with which DAC can translate the digital signals is know as sampling rate
LCD & LED Screens Advantages over CRT(5)
Brighter image
Higher resolution
Thinner screen
Uses less power
Last longer
OLED advantages(6)
Organic layers are thinner, lighter and more flexible
OLED layers can be made from plastic so are lighter
Brighter than LED
No backlighting required so use less power
Can be made into large thin sheets for advertising boards
Very large field of view
DLP projectors (4)
Uses millions of micro mirrors on a DLP chip
Micro mirrors can switch on/off thousands of times a second
Bright white light passes through colour filter on its way to the DLP chip
Light split into primary colours RGB
LCD projectors (6)
Older technology than DLP
Beam of light generated by a bulb
Light sent to group of chromatic-coated mirrors that reflect the light back at different wavelengths corresponding to RGB
Three different light components pass through three LCD screens
Images are then combined using a prism to create full colour image
Finally image passes through projector lens onto a screen
What is an ISP?
a company that provides the user with access to the internet - usually with a monthly fee
gives a user an account and email address
What is a MAC address?
uniquely idenitifies a devic connected to the internet - the MAC address does not change but can be LAA or UAA
Define Operating System
the software running in the background of a computer system - it manages many of the basic functions
What is an interrupt?
a signal sent from a device (or other software) to the processor requesting its attention
What is a buffer?
a temporary memory area in a device
Define computer architecture
how a computer system is designed
What do buses do?
buses move data around the computer and also send out control signals to synchronise the internal operations
What are registers?
high-speed storage areas within the computer
What is a memory unit made up of?
it is made up of addresses and contents
What is a control unit?
it controls the operation of the memory, processor and input/output devices
Give 5 examples of operations/tasks Operating Systems do
human-computer interface (HCI)
multitasking
multiprogramming
batch processing
error handling
load/run applications
management of user accounts
file utilities
processor management
memory management
real-time processing
interrupt handling
security
input/output control
What are examples of devices that do not require an operating system?
ovens
washing machines
Why do some devices not need an operating system?
they carry out simple, unchanging tasks which are initiated by a user pressing a button
What do interrupts cause the processor to do?
temporarily stop what it is doing and service the interrupt
Why are buffers used?
to compensate for the slower operating speed of peripherals when compared to a processor
What do buffers allow processors to do?
to carry on with other tasks
What is an example where buffers are used?
printers
music/video streaming
What is the von neumann architecture?
a concept that holds programs and data in memory
data moves between the memory unit and processor
between processor, memory unit and input/output devices
What does an address bus do?
carries signals relating to addresses between the processor and memory
uni-directional
What does a data bus do?
sends data between the processor, memory unit and the input/output devices
bi-directional
What does a control bus do?
carries signals relating to control and coordination of all activities within the computer, it can be uni-directional or bi-directional due to internal connections
Where must data be represented before it is processed?
in registers
What are 5 different types of registers in the von neumann architecture?
Memory address register (MAR)
Memory data register (MDR)
Arithmetic and Logic Unit (ALU)
Program counter (PC)
Current Instruction Register (CIR)
What does a control unit do?
read instructions
interprets instructions
sends out signals along control bus to synchronise all computer components
What does the fetch part of the fetch execute cycle entail?
the next instructions are fetched from the memory address stored in the PC
this is then stored in the CIR
the PC is incremented by so the next instruction can be processed
What does the execute part of the fetch execute cycle entail?
the decoded instruction is then passed as a set of control signals to the appropriate components of the computer system
What is the Input-Process-Output Model?
It is an abstract way of describing the structure of a system or algorithm. An input is taken, processed, and results in an output. It has the practicality to standardize inputs and outputs, leaving the process unimportant.
input → process → output
What is the extension of the IPO Model?
A feedback loop is added from output to input, and storage is added to the process.
The storage can be used as a cache.
What is the CPU?
It is a central procession unit and controls the manipulation of data. It uses data to perform operations. It includes:
ALU
CU
Registers
What are CPU cores?
A core is a set of CU, ALU, and registers. Some CPUs have multiple cores, which means they can process instructions much more quickly.
What is done by the MDR?
It stores the current data needed to carry out instructions.
What is the ALU?
It is the arithmetic logic unit, where mathematical and logical calculations are done.
What is the CU?
It is the Control Unit, which controls the activities done by the CPU
What are Registers?
They are quick, small stores of data within the CPU.
What is the Von Neumann Architecture?
It contains three major characteristics:
The Main Memory
Stores Binary Values
The CPU
Inputs and Outputs
What is the Fetch-Decode-Execute Cycle?
Fetch:
The Address of the next instruction is copied from the PC into the MAR
The PC is incremented by 1
Decode:
The CU obtains the address of the current instruction from the MAR via the RAM
The RAM returns the data to the MDR via the data bus
Execute:
The data from the MDR is copied into the CIR and decoded by the ALU which results are stored in the ACC
What are the 5 Registers?
Memory Data Register
Memory Address Register
Program Counter
Current Instruction Register
Accumulator
What is done by the MAR?
The MAR stores the address of the current data that the processor requires.
What affects a CPU’s Speed?
The number of cores
The Cache Size
The Clock Speed
What is done by the PC?
The Program Counter stores the address of the next instruction, and it increments once the address is copied into the MAR.
What is done by the AC?
The accumulator stores mathematical and logic results being transferred from or to the memory unit.
What is done by the CIR?
The Current Instruction Register contains the current instruction which is being carried out.
Why do computers need a clock?
The clock provides timing signals to synchronize the circuits. CPUs are designed to operate at their respective clock speeds, the faster the clock speed the faster the CPU.
The faster the clock speed, the faster the fetch-execute-decode cycle.
What is Clock Speed?
The Clock Speed refers to the amount of electrical pulses that the clock inside the CPU can produce every second.
What is the Main Memory (Primary Storage)?
It is what is directly accessible by the CPU and includes RAM, ROM, and Cache.
What in included in the Main Memory?
It is memory directly accessible by the CPU, which includes RAM, ROM, and Cache - although predominantly it refers to the RAM.
What are the two kinds of memory?
Volatile and Non-Volatile. Volatile Memory is temporary and lost when power is, whilst Non-Volatile memory retains data when power is lost.
Memory is normally Volatile, besides ROM. Storage is Non-Volatile
What is the RAM?
Random Access Memory is RAM. Ram has quick read/write times. It loads open programs and operating system data currently in use. Essentially it stores the data of what is currently being used.
What is ROM?
Read-only memory is Non-Volatile, and can only be read and cannot be changed. It contains essential programs, like the programs used to boot the computer.
What is Cache Memory?
It is Volatile, and stores copies of frequently used data. CPU Cache sits between the CPU and RAM and is checked before RAM in the fetch phase. Because it stores commonly used data, it is placed much closer to the CPU, although browsers and storage may also have caches.
What is Virtual Memory?
It is a temporary memory, it is a memory management procedure used when the RAM is full. It is created from secondary storage that is temporarily converted into volatile memory. Data from non-current processes are sent as pages from the RAM to the Virtual Memory, and it is much slower.
What is Flash Memory?
It is Non-Volatile, a part of SSD (Solid-State Memory; non-mechanical). It is more reliable and durable, but can only be overwritten a finite amount of times.
What are the Buses(Connections)?
Buses carry data around the computer, the names are representative of the data they carry. They are a collection of wires through which data is transmitted, and they are:
Data Bus
Address Bus
Control Bus (Instructions)
Which directions can the buses go?
CPU → Address Bus → RAM (UniDirectional)
CPU ←→ Data Bus ←→ RAM (Bidirectional)
CPU ←→ Control Bus ←→ RAM (Bidirectional)
What is the Secondary Storage?
It is storage not directly connected to the CPU and is Non-Volatile.
What are the keywords for Secondary Storage?
Portability
Durability
Reliability
Cost
Capacity
Speed
What is Optical Storage?
It is storage stored through pits and lands. Data is written via laser to burn pits through the disks, light is then shone on the disks in which the reflection of light is used to read data.
It includes:
CD
DVD
Blu-Ray
What are the advantages and disadvantages of Optical Storage?
Advantages:
Good Portability
Can be Rewritten
Disadvantages:
Small Capacity
Easily Damaged
What is Magnetic Storage?
Magnetic Storage uses read/write heads that contain electromagnets. Parts of the disc are magnetized (1) or demagnetized (0) - and the heads read this.
What is Solid-State Storage?
It is a form of flash memory, so it is non-mechanical. Electrons are stored in transistors and capacitors, in which data is stored. When it is connected to power, these electrons ‘flash’ into the device.
What are the Advantages and Disadvantages of Magnetic Storage?
Advantages:
Cheaper
Larger Storage
Disadvantages:
Easily Broken
Noisy and generates heat
What are the Advantages and Disadvantages of Solid-State Storage?
Advantages:
Much Faster
Reliable because non-mechanical
silent
portable
don’t produce heat
Disadvantages:
Expensive
Degrades over multiple read-write cycles
What is Cloud Storage?
Cloud Storage is data stored on multiple servers, in remote locations. Servers use magnetic/solid-state storage. It operates through a web-based API.
