Computer Organisation And Architecture Flashcards
(Hasn’t come up yet) Describe the principles of the operation of a digital camera (6 marks)
- Photo taken by shutter opening and letting light in to lens
- Light is focused on sensor which uses either CCD or CMOS
- sensors made up of millions of transistors which store the data for one or more pixels
- As light hits sensor, it’s converted to electrons and the amounts of charge is recorded for each pixel in digital form
- With light, all colours can be created from RGB - so either 3 different sensors are used or 3 different filters
- Data typically stored in removable storage devices such as programmable ROM or flash memory
- Data usually stored as JPEG/PNG (compressed) or RAW (uncompressed)
- All digital data can be decided and manipulated using specialised software.
How is capability of digital cameras quantified?
By how many megapixels it uses to store images.
Describe the principles of operation of a barcode reader (6 marks) (HASNT COME UP YET)
- A light (usually LED) is passed over an image
- Some form of light sensor is used to measure the intensity of the light being reflected back. This is converted into a current which creates a wave form ( can be achieved using a CCD like digital cameras)
- White areas reflect most light and black the least so using that wave form, able to distinguish patterns of black and white bars
- Waveform is analogue and therefore needs to be converted into digital form using an anologue to digital converter
- Will usually convert with 0 representing black and white representing 1
- Signal decoded into a form which can be interpreted by the software then.
Describe the principles of operation of an RFID reader (RFID came up in 2020 but not on how it works) (6 marks)
- Tag contains a chip which contains the data about an item and modem to modulate and demodulate the radio signals
- The tag also contains an antennae to send and receive signals
- Tags can either be active or passive (have their own power source/will pick up EM power when in range of an RFID reader
- Signals and data can be transmitted in both directions using radio frequencies using range (typical range between 1-100 )
- Tags may be used to track physical location of tagged item or when they may transit data back.
Applications of RFID
- tracking people such as those with Alzheimer’s
- used in electric passports
- contactless payment
- transport and shipments to track deliveries
- tags on high value items like artwork in museums or equipment in hospitals
Describe the operation of a laser printer (6 marks) - came up in 2021
- Rotating drum is coated with chemical which holds electrical charge
- Laser beam pointed at drum and where light hits the drum, the charge is discharged creating the image on the drum.
- As the drum rotates, it picks up toner which is attracted to the parts of the drum which are charged.
- Paper is passed over the drum and the toner is now attracted to the paper and away from the drum.
- Paper is heat treated to fuse the toner onto the paper
Main advantage of using a laser printer?
Speed - about 20 pages per minute! ( home laser printers )
Principles of operation of SSD (4 marks) - CAME UP 2022
- Data is stored electronically unlike in a HDD where there are mechanical and moving parts.
- The data in the SSD is stored in a floating gate transistor - these are special because they can maintain their charge even when power is not connected to it.
- The presence of a trapped charge is indicated with a 1 whilst the absence of a charge is represented as a 0.
- When data is written to the SSD, it must be written one block at a time.
- can mention other points, these just made most sense to me.
Describe the principles of the operation of an optical disk (4 marks) [HASN’T COME UP YET]
READ ONLY DISK
For read only optical disks:
- data is encoded as a series of bumps/pits and lands within the track of the disk
- this is then covered in a film to prevent corruption of data
- when the CD is read, pits and lands are read by the laser which then interprets each as a different electrical signal.
- these electrical signals can be converted into binary codes then.
Describe the principles of the operation of an optical disk (4 marks) [HASN’T COME UP YET]
Writeable DISK!!!!!
- disk is coated in photosensitive dye which is translucent
- when writing to the disk, the laser will alter the state of the dye spot that is coated on the surface making it opaque.
- the dye reflects a certain amount of light
- a write laser alters the density of the dye and a laser interprets the different densities to create the binary patterns which in turn create the data representation.
Important to note write lasers are more powerful than read lasers.
Describe the principles of the operation of an magnetic hard disk (4 marks) [HASN’T COME UP YET]
- constructed of hard metallic material and are tightly sealed to protect from data corruption by dust
- most hard disks contain a stacks of disks which are coated in a thin magnetic film
- changes in direction of magnetism are represented in binary.
- hard disk spins as data is read from and written to HDD.
- actuator arm moves the head of the disk as it spins.
