Redundancy: repeated data that can be shortened

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Quick Questions

Shade in the A or B circle for each question.

1. Which string has more redundancy?

A QXZPLMWEBN

B AAAAAAAAAA

2. What is redundancy in data?

A Repeated or predictable data that can be shortened

B Data that has been deleted by mistake

3. Which image would have the most redundancy?

A A plain blue sky with every pixel the same colour

B A photo of a crowded market with thousands of colours

4. When we remove redundancy by writing WWWWWW as 6W, what happens to the information?

A Some is lost, because we can no longer tell how many W's there were

B None is lost, because we can rebuild WWWWWW

5. Which is an example of spotting a pattern to shorten data?

A Writing ABABABAB as 4 x AB

B Deleting every second letter of ABABABAB

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1AAAAAAAAAA		AThe letter was lost, so the information is gone; it should be 5A
210A		BA shortened form of a repeated run that keeps all the information
3A row of pixels that are all the same colour is redundant data		CThere are no repeats or patterns in ABCDEFGH, so it has no redundancy to remove
4Spotting a pattern lets you store repeated data in fewer characters		DBBBBBBBB
5ABCDEFGH can be shortened a lot because it has lots of redundancy		EA run of repeated characters: redundant data that could be stored in a shorter form
6AAAAA shortened to 5 (the letter is dropped)		FWWWWWW -> 6W

Definitions

redundancy

Fill in the Blanks

Complete each line of code by filling in the missing parts.

AAAAAAAA is stored as _A

Repeated or predictable data is __________

WWWWWWBB -> 6_2B

ABABABAB = 4 x __

row = RRRRRRRRRR short = __R

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A text ← AAAABBB

B A repeats 5 times

C B repeats 3 times

D short ← 5A3B

Question 2

A row ← R R R B B

B R is repeated 4 times

C B is repeated 2 times

Question 3

A pixels ← W W W W W W

B all pixels are the same

C store ← 5W

Question 4

A msg ← ZZZZZZ

B count ← 9

C short ← 6Z

Question 5

A data ← ABABABAB

B pattern ← AB

C repeat ← 2 times

D short ← AB x 4

Answer Key

Redundancy: repeated data that can be shortened

Section A: Quick Questions

B — AAAAAAAAAA

A — Repeated or predictable data that can be shortened

A — A plain blue sky with every pixel the same colour

B — None is lost, because we can rebuild WWWWWW

A — Writing ABABABAB as 4 x AB

Section B: Match the Pairs

AAAAAAAAAA → A run of repeated characters: redundant data that could be stored in a shorter form

10A → A shortened form of a repeated run that keeps all the information

A row of pixels that are all the same colour is redundant data → BBBBBBBB

Spotting a pattern lets you store repeated data in fewer characters → WWWWWW -> 6W

ABCDEFGH can be shortened a lot because it has lots of redundancy → There are no repeats or patterns in ABCDEFGH, so it has no redundancy to remove

AAAAA shortened to 5 (the letter is dropped) → The letter was lost, so the information is gone; it should be 5A

Section C: Definitions

redundancy — Repeated or predictable data, like a run of the same letter or colour, that can be stored in a shorter form without losing any information.

Section D: Fill in the Blanks

AAAAAAAA is stored as 8A

Repeated or predictable data is redundancy

WWWWWWBB -> 6W2B

ABABABAB = 4 x AB

row = RRRRRRRRRR
short = 10R

Section E: Spot the Error

A — The text only has 4 A's, but the next line says A repeats 5 times. The line should be text ← AAAAABBB so the repeated data matches the short form 5A3B.

A — The row shows only 3 red pixels, but the next line says R repeats 4 times. The row should be R R R R B B.

C — There are 6 white pixels in a row, so the short form must be 6W. Writing 5W would lose information when the data is rebuilt.

B — The message contains 6 Z's, so the count should be 6. A wrong count would not match the short form 6Z.

C — The pattern AB appears 4 times in ABABABAB, not 2. Spotting the pattern and counting its repeats correctly is what lets us shorten it to AB x 4.