2015 Old Spec

Question 4

--- Create a folder/directory Question4 for your new program.

The algorithm, represented using pseudo-code in Figure 4, and the variable table, Table 3, describe a program that calculates and displays all of the prime numbers between 2 and 50, inclusive.

The MOD operator calculates the remainder resulting from an integer division eg 10 MOD 3 = 1.

If you are unsure how to use the MOD operator in the programming language you are using, there are examples of it being used in the Skeleton Program.

Figure 4

OUTPUT "The first few prime numbers are:" FOR Count1 = 2 TO 50 DO Count2 = 2 Prime = "Yes" WHILE Count2 * Count2 <= Count1 DO IF (Count1 MOD Count2 = 0) THEN Prime = "No" ENDIF Count2 = Count2 + 1 ENDWHILE IF Prime = "Yes" THEN OUTPUT Count1 ENDIF ENDFOR

Table 3

Identifier	Data Type	Purpose
Count1	Integer	Stores the number currently being checked for primeness
Count2	Integer	Stores a number that is being checked to see if it is a factor of Count1
Prime	String	Indicates if the value stored in Count1 is a prime number or not

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What you need to do

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Write a program for the algorithm in Figure 4. Run the program and test that it works correctly. Save the program in your new Question4 folder/directory.

11 Marks

+ 1 Mark for testing screenshot

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Additional Question

--- Describe the changes that would need to be made to the algorithm shown in Figure 4, so that instead of displaying the prime numbers between 2 and 50, inclusive, it displays all the prime numbers between 2 and a value input by the user, inclusive.

3 marks