2017 A Level

Question 10

One method that can be used to compress text data is run length encoding (RLE). When RLE is used the compressed data can be represented as a set of character/frequency pairs. When the same character appears in consecutive locations in the original text it is replaced in the compressed text by a single instance of the character followed by a number indicating the number of consecutive instances of that character. Single instances of a character are represented by the character followed by the number 1.

Figure 9 and Figure 10 show examples of how text would be compressed using this method.

Figure 9

Original text: AAARRRRGGGHH

Compressed text: A 3 R 4 G 3 H 2

Figure 10

Original text: CUTLASSES

Compressed text: C 1 U 1 T 1 L 1 A 1 S 2 E 1 S 1

What you need to do

Task 1

Write a program that will perform the compression process described above. The program should display a suitable prompt asking the user to input the text to compress and then output the compressed text.

Task 2

Test the program works by entering the text AAARRRRGGGHH.

Task 3

Test the program works by entering the text A.

Evidence that you need to provide

Include the following in your Electronic Answer Document.

Your PROGRAM SOURCE CODE. [12 marks]

SCREEN CAPTURE(S) for the test showing the output of the program when AAARRRRGGGHH is entered. [1 mark]

SCREEN CAPTURE(S) for the test showing the output of the program when A is entered. [1 mark]