Computer Architecture: Principles of Operations Flashcards
What is a Barcode?
A barcode is a means of representing data in machine-readable form. They are printed diagrams that consist of light and dark portions. They contain information which can be read by a computer using a barcode reader. There are two main types of barcode: 1D and 2D.
how are 2D Barcodes different to 1D Barcodes
Can contain more information in the same amount of space as a 1D barcode
but require more processing in order for the information to be extracted.
Barcode: Principles of operation
- A light from a laser illuminates the barcode
- The white areas reflect more light the the black bars
- The reflected light is captured by one or more photoelectric cells that generate a set of electrical pulses that correspond
- These pulses are converted to a binary number that represents the code
- Check Digit
What happens if a barcode fails to scan?
If a barcode fails, the reader will continue to scan until the barcode is read successfully. Barcode readers can scan barcodes 1000s of times a second, so the time delay by rescanning is hardly perceptible to humans
Two sensors commonly used in Digital Cameras?
Two sensors commonly used in digital cameras are CMOS (complementary metal oxide semiconductor) and CCD (charge coupled device) which both convert incident light into electrical charge.
Digital Camera: Principles of Operation
- Light enters through / is focussed by the lens; on to (an array of sensors on) the sensor chip A. light sensors capture / record light (intensity) A. CCD as sensor;
- Each sensor produces an electrical current / signal;
- The signal represents a pixel;
- An (ADC) converts measurement of light intensity into binary/digital data;
- (Colour) filter is applied to generate separate data values for red, green and blue colour components;
- The pixels are recorded as a group / array;
What is a Bayer Filter?
A Bayer filter is a special colour filter used in digital cameras that
has the same number of green filters as red and blue combined.
What does using a Bayer filter cause for the image?
It produces an image that is a closer approximation of what the human eye, which is most sensitive to green light, sees.
What is a laser printer?
A laser printer is an output device that produces images on paper from digital signals.
Laser printers, which print whole pages at a time, consist of a laser light source, a mirror, a
drum, a toner roller and fusers.
Laser Printer: Principles of Operation
- Print drum coated in positive/negative charge
- Printer generates a bitmap of the page from the data
- Laser beams directed at draws on the print drum via a rotating mirror
- Laser is modulated, and removes electric charge on the drum where the image should be dark/black
- Toner is also given the same charge, and the charged drum picks up toner. For colour it is fused to paper
What is RFID and where can it be used?
RFID, which stands for radio frequency identification,
is a method of transferring information wirelessly
between a tag and a reader. RFID is used in
contactless credit and debit cards as well as in some
hotel room cards.
RFID: Principles of Operation
- Reader sends radio frequency wave to the antenna of the RFID tag
- The RFID tag chip is energized by the reader
- The transponder (in the tag) sends the data signal and the reader receives it
What is the Hard disk drives platter?
The platters are circular metallic disks which have one or both sides magnetised, allowing data to be stored. It spins while in use around a spindle. It is divided into tracks and sectors with data represented by magnetising spots on the disk.
What is the Hard disks Head?
The read/write head reads magnetic data from the platter
What is the Hard disks Actuator arm?
This arm allows the head to access all parts of the platter through in and out movement. They allow you to read data in a random fashion.
