3.3 fundamentals of data representation

0 + 0

0

1 + 0

1

1 + 1

10 ( put down the 0 and carry the 1 )

1 + 1 + 1

11 ( put down the 1 and carry the other 1 )

how to convert binary to denary

use the conversion table

how to convert denary to hexadecimal

convert denary to binary

split the conversion table in half

use the split conversion tables both with 8/4/2/1 to convert the binary into what would normally be denary

if the number is above 9 then go into letters

negative binary numbers

work out the denary number in binary if it was positive

reverse the values up until the bit column with a 1 in it.

images

represented using binary numbers

created using a grid of pixels

pixels

the smallest part of an image

short for picture elements

1 bit images

can only have 2 possible colours

0 = white 1 = black

2 bit images

can only have 4 possible colours

00 = white 11 = black 10 = red 01 = blue

how to work out the number of colours

2 to the power of the number of bits

colour depth

the amount of colours available to be used in an image

what will happen if you increase colour depth

* increase the detail of the image
* increase the file size of the image as more bits need to be stored about each pixel

resolution

the ability to distinguish from 2 points

what happens if you increase the resolution

* the clearer the image and the more detail it has
* the larger the file size as data has to be stored about each pixel

how do you calculate the image file size

number of pixels(height x width) x colour depth

character set

all the characters that can be represented in a computer system

ASCII

american standard code of information interchange

how many bits did the original ascii account for

7 bits - 128 characters

how many bits did the extended ascii account for

8 bits - 256 characters

what language was ascii used for

english

unicode

universal binary language

Unicode was made because ASCII couldn’t represent all the characters in all the different languages

how many bits does Unicode account for

16 bits - 65,356 characters

analogue sound

waves that are continuously changing in value e.g our voice

they cannot be understood by a computer

digital sound

sound waves which are created from samples of analogue waves,

represented by binary and can be understood by the computer

how do we convert analogue sounds to digital

the analogue sounds can be picked up by a microphone and sent to an ADC (analogue to digital converter)

they are then converted into binary values and stored into the computer

sample rate

the number of times a sound is sampled per second measured in hz

sample resolution

number of bits used to represent sound levels

I.e how clear the sound is

bit rate

the space available to store each sample and is measured in kilobits per second

how to calculate sound file size

sample rate x sample resolution x length in seconds

binary shift

when a binary number is shifted one direction

if it is shifted to the left on the binary table the value multiplies by 2

if it is shifted to the right on the binary table the value divides by 2