Unit 2 Flashcards
(26 cards)
What is a bit
A single 0 or 1
Data needs to be before being processed by a computer
converted into binary format
How do we convert binary to denary
Starting from the right most digit, put a “1” above it. Then put a “2” to the digit to the left of that, then a “4”. Keep on doubling until you get to the max number of digits. Then multiply, the binary digits with their numbers on top and add it all
How do we convert denary to binary
With the same table for the “binary to denary” (where it goes from 1 to 128), you need to see if the denary number is larger than the largest number for binary (ie: 128). If so, put a 1 under there and if not put a 0 and continue to the next one.
How do we convert denary to hex and vice versa
take the number and divide by 16. Take the whole number and convert it to hex.
take the remainder and convert that to hex: Put the 2 numbers together and that’s the finish
To convert hex to denary you need to multiply the first number by 16, then add the 2nd number
Hex base 16:
0 1 2 3… 9 A B C D E F
How do we convert binary to hex and vice versa
Take the 1st 4 numbers of binary, then convert to hex (1st digit)
Take the next 4 numbers of binary, then convert to hex (2nd digit)
Convert the first hex digit to binary (1st 4 numbers) then do the next
Rules for adding binary
0 + 0 = 0
0 + 1 = 1
1 + 1 = 0 carry 1
1 + 1 + 1 = 1 carry 1
what is an overflow error
when a 1 needs to be carried over to the next digit but you’re on your eight digit, so you need a ninth meaning you need an extra digit of storage which you dont have
What effect does a binary shift have on the result and why might it not be accurate
Divides by 2 every shift
If you shift but get rid of a 1 (ie: when shifting backwards you lose a 1 that was in the 1s column) then you won’t get an exact result. It will be an integer but the real result will be decimal
How do we calculate check digits
Give the weight of each ISBN number on the check with “131313..”
Multiply each IBSN number with the weight attached
Add all the numbers
Find the remainder when divided by 10
subtract that from 10
How is each character represented in binary
each character is represented by an 7 digit binary number, with uppercase, lowercase and punctuation and symbols all having different numbers
This is called the ASCII code
An eighth character is sometimes used for 128 extra characters (mostly special characters)
What is a character set
A defined list of characters that are recognised and can be stored in a computer system
what is unicode
A separate character set that uses 16 bits to display characters of every language + special characters
A bitmap graphic is made up of
Individual pixels
Each pixel is made up of
Binary
The more bits in an image the more _____
colours
Formula for number of colours available in an image (colour bit depth) and what is the effect of this
2^num of bits
higher bit depth means greater range of colour hence better quality
What is image metadata and what can it contain for images
Data about data: Information about the data shown
For an image this may contain:
Colour depth
resolution
Date created
Author
How do we calculate image file size in bytes
bit depth * resolution (height*width) / 8 = size in bytes
How is sounds sampled (turned from analogue to digital)
1) The analogue wave is put in a sampler
2) Amplitude of wave is measured at different time intervals
3) Each sample/measurement is stored as a binary digit
4) The binary number for each sample is stored sequentially
The audio bit depth is known as the ___ ___ and it is measured by…
sample resolution
take a 4 bit resolution. The sample resolution will go to 15 as the formula is 2^number of bits. 2^4 is 16 so there are 16 different digits (0-15)
What is the sample rate
The number of samples per second. The higher frequency of samples means the closer it will get to the original analogue sound
measured in hz
How do we calculate sound file sizes
sample rate * resolution * seconds
What is lossy compression
Permanently removes some data
Recreates the file with remaining data and algorithms which guess the missing parts
Won’t be the exact same as original
Much smaller file size
