Data representation Flashcards
What are the only two things computers understand, and how are they represented?
1 = on 0 = off
What is the decimal number system?
10 digits from 0-9, often referred to as ‘base 10’
What is the binary number system?
2 digits from 0-1, often referred to as ‘base 2’
What does a bit represent?
A single 0 or 1
What does a nibble represent?
4 bits, or half a byte
What does a byte represent?
8 bits, or 1 character of text
What does a kB represent?
1000 bytes
What does a MB represent?
1000 kilobytes
What does a GB represent?
1000 Megabytes
What does a TB represent?
1000 Gigabytes
Order the following from smallest to largest:
GB, kB, bit, MB, nibble, byte, TB
bit, nibble, byte, kB, MB, GB, TB
Convert 10100110 to denary
166
Convert 11101001 to denary
233
How do you know if a binary number is odd or even?
If the number is odd, the final digit will be a 1
Convert 58 to binary
00111010
Convert 239 to binary
11101111
What is the hexadecimal number system?
16 digits from 0-9 & A-F, often called ‘hex’
How do you convert a binary number into hex?
- Divide the binary number into groups of four
- Work out the denary value for each group
- Convert each denary number into hex
How do you convert a hexadecimal number into binary?
- Convert each hex number into binary using 4 bits
2. Combine the 4 bit strings
Convert E9 to binary
11101001
Convert C6 to binary
11000110
How do you convert a denary number into hex?
- Convert the denary number into binary
- Convert binary to hex -
(1. Divide the binary number into groups of four - Work out the denary value for each group
- Convert each denary number into hex)
Why is hexadecimal better than binary?
It is much shorter than binary, and less error prone
Binary addition: 0 + 0 =
0
Binary addition: 0 + 1 =
1
Binary addition: 1 + 0 =
1
Binary addition: 1 + 1 =
0 Carry 1
Binary addition: 1 + 1 + 1 =
1 Carry 1
What is it called when there are more bits after a binary addition then the computer can handle?
Overflow error
How do you divide a binary number?
Shift the bits one to the right for every factor of two, e.g. divide by 2: 1 shift, divide by 4: 2 shifts
How do you times a binary number?
Shift the bits one to the left for every factor of two, e.g. divide by 2: 1 shift, divide by 4: 2 shifts
How does a loss of accuracy occur when multiplying or dividing a binary number?
When a ‘1’ bit is removed from a shift left or right
How do we define memory?
Where binary data (0s and 1s) is stored
What is a pixel?
A pixel is a single point in a graphical image
A pixel is a single point in a graphical image. How are pixels arranged?
Pixels are arranged into rows and columns
A pixel is a single point in a graphical image. How does a VDU screen divide up the image?
Similar to a mosaic, a VDU screen divides an image into millions of pixels
How did the word pixel come about?
Bitmap images are made up of PICture ELements of PIXELS.
What are bitmap images made up of?
Bitmap images are made up of PICture ELements of PIXELS.
What is the smallest identifiable area of an image?
A pixel
What is each pixel made up of?
Each pixel is
1) made up of a single colour
2) is given a binary value which represents that colour - e.g. 11000000 might equal red
How do you change a pixels colour?
Change the binary value
What is image resolution or resolution?
The concentration of pixels in a specific area
How do you define the area of the pixel resolution?
This is defined by the image width and height of the pixels e.g. 3264x 4897
what is the screen resolution?
72 dpi
What is the print resolution?
300 dpi
Each pixel is given a binary number.
What does black and what does white equal?
1 = black
0 = white
Each pixel can have 1, 2, 3, 4 or more binary ‘bits per pixel’ why?
More bits= more colours
2 bits - ie the pixel is either 1 or 0 allows just black and white.
whereas 2 bits per pixel allows 4 colours and 4 bits per pixel allows 16 colours
What will make the file size of a picture bigger?
The number of colours
Bits per pixel
The size of the image
The higher the number of bits the greater the number of ?
Colours
Image megadata is information other than image data that is stored with a file. What does it include? (4 things)
1) colour depth in bits per pixel
2) resolution (height and width in pixels)
3) date created
4) Author
Summary:
A bitmap graphic is made up of __________________
Each _______ is represented in binary
The ________________________ determines the number of available colours for an image
Image _________ holds data about the image such as
___________________________________________
The greater the _________ of the image, the greater the file size
Answer
A bitmap graphic is made up of individual pixels
Each pixel is represented in binary
The number of bits per pixel determines the number of available colours for an image
Image metadata holds data about the image, such as colour depth, resolution, date created, author
The greater the resolution of the image, the greater the file size
What are names of image files? (3 names)
BMP JPEG GIF PNG TIF
What is ASCII?
American Standard Code for Information Interchange
In 1960, the American Standard Association agreed on a set of codes to represent the main characters in the English language - this is known as ASCII - (
American Standard Code for Information Interchange)
In 1960, the American Standard Association agreed on a set of codes to represent the main characters in the English language. What is this known as?
ASCII - (
American Standard Code for Information Interchange)
What does ASCII stand for and what is it?
ASCII - (
American Standard Code for Information Interchange)
In 1960, the American Standard Association agreed on a set of codes to represent the main characters in the English language - this is known as ASCII
How does ASCII allocate codes?
One for every lower case letter, upper case, numeric symbol, punctuation marks etc - 127 in total
ASCII has 127 codes.
How many bits are needed to store 127 codes?
7
0000000
through to
1111111
ASCII was agreed when 7 bit machines were standard. What has happened since?
Now there are 8 bit machines and so many more possible codes.
WIth 8 bit machines, ASCII character sets can be up to 256 characters. What is the problem with this?
Some languages such as mandarin and Japanese use thousands of different characters and so they cannot fit into a byte or an ASCII machine.
As computers developed and 16 bit computers were introduced, a new character set was developed to cover all the languages of the world. What was it called?
Unicode
As computers developed and 16 bit computers were introduced, a new character set was developed to cover all the languages of the world. It was called Unicode how does it differ from the original ASCII?
All 127 characters of the original ASCII are in Unicode but with many more added on
