2.2 Data Representation (B03)

Question 1

ASCII

Answer 1

American Standard Code for Information Interchange

• based on 7-bit binary numbers (128 possible valkues)

Question 2

text file - and why are they good?

Answer 2

only contains character-by-character encoding of the text

They are cross-platform: a text file on Windows is the same text file on a Mac, on Linux etc.
Most operating systems come with basic tools to view and edit them (Notepad on Windows).

Question 3

what 2 ASCII values do you need to know

Answer 3

A = 65
a = 97
32 GAP BETWEEN

Question 4

extended ASCII (ex)

Answer 4

uses eight bits, giving a character set of 256 characters. This allows for special characters such as those with accents in languages such as French and Spanish.

still not enough for all of the worlds languages

Question 5

unicode (ex)

Answer 5

Uuses between 8 and 32 bits per character, so it can represent characters from languages from all around the world.
It is commonly used across the internet.
larger than ASCII, it might take up more storage space when saving documents
Global companies, like Facebook and Google, could not operate with just the ASCII character set because their users communicate in many different languages.

Question 6

character set

Answer 6

the defined list of characters recognised by an encoding system. So, for example, ASCII has a character set that contains 128 characters.

Question 7

exam question!

Answer 7

i) Each character is assigned a unique character code
Each letter is converted to its character code (which is a binary number)

ii) 0100 0011 0100 0001 0100 0010.

iii) ASCII uses 8 bits…
…and so can only represent 255 / 256 distinct characters…
…many more characters are needed for coping with all languages (e.g. Unicode 16bits)
ASCII does contain characters used in some languages

Question 8

problem with ASCII

Answer 8

uses 7-bits - 128 characters - not enough to represent all of the worlds languages

unicode (16 bits) generally used instead

Question 9

pixel

Answer 9

smallest element of a bitmapped image

Question 10

metadata

Answer 10

basically data about the data

contains (for bmp):
No. of columns in the image
No. of bits in the binary numbers used to store the colours (in this example on the right: 2).

(also creation date, mod. date etc)

Question 11

resolution

Answer 11

number of pixels per inch when the image is displayed.
Higher resolution -> more pixels per inch

Question 12

image size

Answer 12

the number of pixels (width × height) - different from physical size or file size

Question 13

bit depth (colour depth)

Answer 13

number of bits for each colour

Question 14

bit pattern

Answer 14

a unique string of binary digits used in a representation

Question 15

calculating file size (for pictures)

Answer 15

File size = width × height × colour depth

Question 16

exam question!

Answer 16

An image is made up of / consists of pixels
A pixel can be one colour
Each colour has a unique / corresponding binary number
Each pixel / square is given the binary number of its colour
The binary numbers are stored in order in the file
E.g. White = 000, Red = 010, Blue= 110, top line would be 000000010010010110110

Question 17

exam question!

Answer 17

To store data / information about the image / data
E.g. Dimensions / height / width / No. of bits per pixel / Colours used / location / date / file type

Question 18

exam question!

Answer 18

Answer: 2 from
Fewer bits are needed per colour
which means fewer bits per pixel
Any example from diagram