Input output devices Flashcards
what do barcodes do
Barcode readers are used to quickly and accurately scan barcodes
when are 2d barcodes used
- ticketless entry to concerts
- ## boarding trains
advantages of laser scanners
- available in a variety of forms
- reliable and economical for low volume applications
examples of laser scanners
- CCD readers
- Camera based readers - used for age verification or event ticketing
how do digital cameras work
- shutter opens to let light on CCD
- Each sensor produces an electrical current/signal
- The signal represents a pixel;
An (ADC) converts measurement of light intensity into binary/digital data;
-filter is applied to generate separate data values for red, green and blue
colour components; - The pixels are recorded as a group / array;
what does a digital camera use
a CCD or CMOS
advantages of CCD sensor
- produces higher quality images
- used in higher end cameras
- more reliable since the technology has been around longer
disadvantages of a CCD compared to a CMOS
- cost of power consumption, uses up to 100 times that of CMOS sensor
what are RGB filters used for
to separate out wavelengths
how do RFIDs work
- RFID tag contains circuitry and antenna
- RFID reader transmits electromagnetic field
- signal activates current in RFID tag
- RFID reader converts radiowaves back into binary
how does a laser printer work
- Bitmap of image built in memory from page description.
- charge applied to drum.
- Laser beam directed at drum.
- Mirror is used to direct laser beam.
- Where laser strikes drum charge is neutralised
- charge applied to toner.
- Toner sticks to drum based on charge
- Paper passed over drum and toner transfers to it.
- charge applied to paper assists with transfer.
- Heater fuses toner onto paper.
- four drums are required.
how to prevent sticking in laser printing
the electric charge on the drum is removed
how does a barcode work (light source)
- light source directed at barcode
- prism moves light beam across barcode
- light is reflected back
- black reflects less light, white reflects more
- light sensor measures the intensity of light reflected back
- and converts it into binary
digital camera barcodes process
- CMOS sensor measures light intensity at a point
- sensor outputs voltage, dependent on light intensity
- voltage turned into binary via ADC
- image processing software analyses image
- and identifies black and white bars in barcode
How do optical discs read
- laser shone on disk
- light is focused on spot on track
- light is reflected back from disk
- amount of light reflected is measured
- disc spins at constant linear velocity
hows data represented using a disc
- data is stored on one track
- continuation of pit reflects light whereas transition between land and pit scatters light
- transition between land and pit indicates a 1 and continuation of land/pit represents 0
advantages and disadvantages of secondary storage
advantages - provides non-volatile memory that retains information even when the computer is turned off. This enables long-term storage of programs
disadvantages - secondary storage is not directly accessible to the processor and has slower access speeds
problems with primary storage
its volatile, if you turn the computer off, data gets lost
characteristics of hard disk
- they help fit more data in the same physical space
- they are more densely packed
- ## use magnetic storage to store data.
what is latency
the time taken to read/write disk data
examples of latency
seek delay - the time the head takes to move across the disk
rotational delay - the time the disk takes to move to the correct sector underneath the read/write head
examples of optical disk formats
- read only
- recordable
- re writeable
recordable formats features
uses a transparent dye that becomes opaque when heated by a laser
rewriteable format features
uses a laser to change the state of a phase change alloy and a magnet to set the new state
what is a solid state disk
a disk that compromises millions of NAND memory cells
how do optical disks write
- a high powered laser burns pits into the CD surface
- a low powered laser detects the reflection from pits and lands
- only a put end deflects the laser light end and is read as a binary 1
- the point where the pit starts or ends causes the light to scatter
Definition of drive
a device that reads and writes data from secondary storage
What is media?
What the data is actually stored on
Advantages and disadvantages of optical storage
- low cost per gigabyte
- light weight
- portable
- slow access speeds
- have lower storage capacities compared to hard disks, making them suitable for storing smaller amounts of data.
advantages and disadvantages of magnetic storage
- cheap
- large capacity, so popular choice for archives
- low cost per unit capacity
BUT
- slow access time and fragile/not robust(as it has a lot of moving parts
how fast does a disk spin
speeds of up to 10,000 RPM
features of a hard disk
- a drive head moves across the disk to access different tracks and sectors
- data is read or written to the disk as it passes under the drive head
- holds the operating system, application, and user data
what happens to the drive head when it’s not being used
it’s parked to one side of the disk in order to prevent damage
hard disk uses and why
huge capacity makes them suitable for desktop surfaces
how much data can a CD ROM hold
650MB
how much data can a blue ray hold
50GB
uses of optical storage
- small backups and storing music
how do SSDs work
- data is stored electronically, data is stored in floating gate transistors
- electrons are trapped between oxide layers
- NAND memory is used
- data is organised into blocks
- a whole block of data must be written
- a block must be erased before it is overwritten
- controller manages the organisation of the data
why is an SSD is a better choice than a magnetic hard disk
- SSDs have lower power drain; which is important as the life blogger will run on
battery;
- SSDs have lower power drain; which is important as the life blogger will run on
- SSDs are less likely to be damaged if dropped; which is important as the devices will
be worn and carried around; - SSDs have faster access time; which could allow more data to be stored per second
(which may allow finer detail); - SSDs are silent; which means they will not disturb the users;
- SSDs are lighter/less obtrusive/smaller; which is important for a device worn around
the neck; - SSDs produce less heat; which makes them more comfortable to wear;
adv and disadv of laser printers
- fast printing speeds, making them ideal for environments where large volumes of documents need to be printed quickly.
- Laser printers produce crisp, sharp text and images with high resolution.
- Laser printers consume more energy during operation compared to inkjet printers
- there is a risk of toner smudging or streaking
- higher upfront cost
advantages and disadvantages of rfids
advantages:
- Can be encrypted, reducing the chance of data theft.
- durable and can be used loads of times
- Can read RFID tags from a greater distance than barcodes.
- RFID minimizes human intervention, reducing errors and saving time.
disadvantages
- Tags and readers can be expensive
- Has shorter read ranges compared to some other tracking technologies
advantages and disadvantages of digital cameras
advantages
- Can store thousands of photos digitally.
- Photos are easily edited and shared digitally without quality loss.
- Photos can be viewed immediately after taking them.
disadvantages
- expensive
- Large photo files require storage space and organization.
- Smaller sensors may lead to lower image quality, especially in low light.
advantages and disadvantages of barcode readers
advantages
- reduces the risk of human error associated with manual data entry
- Fast scanning with a high degree of accuracy.
- Easy to use and understand
- cheap to implement
disadvantages:
- Barcodes can become unreadable if scratched or dirty.
- Can be easily copied or forged, offering no data encryption.
- Holds less information than RFID or QR codes
- Must be directly scanned, making it less efficient for bulk scanning.
- Typically used for one-time applications, without durability for long-term use.
-
what are rfids
RFIDs provide a wireless means of identifying and tracking objects,
disadvantages of SSDs
Lower latency but faster transfer
speeds than a magnetic disk drive.
types of magnetic storage
- hard disk drives
what does a read/write head do
moves to the correct location, then reads or writes data
difference between optical and magnetic storage
- magnetic uses a read/ write head
- optical use pits and lands
what does select , update, insert do in retail database
- SELECT query used to check if there is already a record for the product
- UPDATE statement used to increase stock level if the product is already in database
- INSERT used to create new record for product if it is not already in the database
Explain why a laser printer with a built-in wireless network adapter is likely to be a
suitable choice of printer for a small office.
- Low cost per printed page/toner is cheaper than ink
- Prints many pages per minute at high speed;
- Options to install a variety of paper trays
handling options; - Toner will not dry out
- toner does not expire as quickly as ink;
- High resolution output
Why having a wireless adapter is suitable:
- Easy to share printer between many devices;
- Can print directly from computers with WiFi no need to install a network
- Printer can be managed remotely
- WiFi should be fast enough for likely number of users
- WiFi should have sufficient range for devices to connect (as small office);
