Notes

conversions
binary to hexa- binary to sets of 4, each of which is a power of 2 from the right to left.
binary to denary- take binary from right and multiply with power of 2, then add all the products.
denary to binary- take the no. and divide by 2, remainders are binary.
denary to hexa- divide by 16 and find remainder
hexa to denary- take hexa from right and multiply with powers of 16, then add all products.
hexa to binary- from left to right convert each digit into binary and write left to right
barcodes
read by red led, reflected light from white part is read by sensors
raw scanned data is converted to digital data
can hold 30 digits from 1 through 9
QR codes-
can hold over 7000 digits
made up of matrix with dark squares
easily scannable by phones
can store URLs so easier so helpful for
Digital Cameras-
media can be shared via Bluetooth or USB ports
storage can be saved by deleting unnecessary photos
microprocessor helps in:
Adjust shutter speed
focus on image
aperture size is adjusted
Keyboards-
connected via USB or wirelessly
in mobile phones, usually virtual or touchscreens
Each character has ASCII value
each character pressed is converted to data signal which computer interprets
Pointing device-
used to 'click' on an icon
wireless or usb
traditional mouse has ball
move in x-y direction, optical mouse
two types: traditional and trackerball
trackerball used in places with less desk space
most computers have a touchpad
Microphones-
built-in or external (wireless or USB)
picks up sound, diaphragm vibrates making electrical signals and converts to digital values
voice recognition compares digital wave pattern caused by diaphragm
speech recognition, microphone recognises words by converting sound to digital form and then compared with the built in dictionary and the word is suggested by the software
Touchscreens-
Capacitive:
has layers of glass which when pressed creates an electrical field changing the path of current determining the coordinates of touch
Infra-red:
-heat sensitive:
needs warm object to carry out an operation
-Optical:
uses different sensors in a grid format to determine the point of touch
Resistive:
uses upper layer of polyester and bottom layer of glass
when upper layer is touched, it completes a electrical current
signal interpreted by microprocessor, calculation determines coordinates