Data representation Flashcards
1
Q
What are the only two things computers understand, and how are they represented?
A
1 = on 0 = off
2
Q
What is the decimal number system?
A
10 digits from 0-9, often referred to as ‘base 10’
3
Q
What is the binary number system?
A
2 digits from 0-1, often referred to as ‘base 2’
4
Q
What does a bit represent?
A
A single 0 or 1
5
Q
What does a nibble represent?
A
4 bits, or half a byte
6
Q
What does a byte represent?
A
8 bits, or 1 character of text
7
Q
What does a kB represent?
A
1000 bytes
8
Q
What does a MB represent?
A
1000 kilobytes
9
Q
What does a GB represent?
A
1000 Megabytes
10
Q
What does a TB represent?
A
1000 Gigabytes
11
Q
Order the following from smallest to largest:
GB, kB, bit, MB, nibble, byte, TB
A
bit, nibble, byte, kB, MB, GB, TB
12
Q
Convert 10100110 to denary
A
166
13
Q
Convert 11101001 to denary
A
233
14
Q
How do you know if a binary number is odd or even?
A
If the number is odd, the final digit will be a 1
15
Q
Convert 58 to binary
A
00111010
16
Q
Convert 239 to binary
A
11101111
17
Q
What is the hexadecimal number system?
A
16 digits from 0-9 & A-F, often called ‘hex’
18
Q
How do you convert a binary number into hex?
A
- Divide the binary number into groups of four
- Work out the denary value for each group
- Convert each denary number into hex
19
Q
How do you convert a hexadecimal number into binary?
A
- Convert each hex number into binary using 4 bits
2. Combine the 4 bit strings
20
Q
Convert E9 to binary
A
11101001
21
Q
Convert C6 to binary
A
11000110
22
Q
How do you convert a denary number into hex?
A
- 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)
23
Q
Why is hexadecimal better than binary?
A
It is much shorter than binary, and less error prone
24
Q
Binary addition: 0 + 0 =
A
0
25
Binary addition: 0 + 1 =
1
26
Binary addition: 1 + 0 =
1
27
Binary addition: 1 + 1 =
0 Carry 1
28
Binary addition: 1 + 1 + 1 =
1 Carry 1
29
What is it called when there are more bits after a binary addition then the computer can handle?
Overflow error
30
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
31
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
32
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
33
How do we define memory?
Where binary data (0s and 1s) is stored
34
What is a pixel?
A pixel is a single point in a graphical image
35
A pixel is a single point in a graphical image. How are pixels arranged?
Pixels are arranged into rows and columns
36
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
37
How did the word pixel come about?
Bitmap images are made up of PICture ELements of PIXELS.
38
What are bitmap images made up of?
Bitmap images are made up of PICture ELements of PIXELS.
39
What is the smallest identifiable area of an image?
A pixel
40
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
41
How do you change a pixels colour?
Change the binary value
42
What is image resolution or resolution?
The concentration of pixels in a specific area
43
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
44
what is the screen resolution?
72 dpi
45
What is the print resolution?
300 dpi
46
Each pixel is given a binary number.
| What does black and what does white equal?
1 = black
0 = white
47
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
48
What will make the file size of a picture bigger?
The number of colours
Bits per pixel
The size of the image
49
The higher the number of bits the greater the number of ?
Colours
50
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
51
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
52
What are names of image files? (3 names)
```
BMP
JPEG
GIF
PNG
TIF
```
53
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)
54
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)
55
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
56
How does ASCII allocate codes?
One for every lower case letter, upper case, numeric symbol, punctuation marks etc - 127 in total
57
ASCII has 127 codes.
| How many bits are needed to store 127 codes?
7
0000000
through to
1111111
58
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.
59
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.
60
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
61
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
