The factorial of a number is the product of all the integers from 1 to that number. For example: factorial of 5 is given by 1 × 2 × 3 × 4 × 5 = 120 factorial of 7 is given by 1 × 2 × 3 × 4 × 5 × 6 × 7 = 5040 factorial of 1 = 1 Note: factorial of 0 = 1 A function Factorial() will: • be called with an integer number as a parameter • calculate and return the factorial of the number • return -1 if the number is negative.

Mark scheme

Marking points from the official mark scheme (May/June 2022). The mark or mark type is shown in brackets.

1. [6] (a) Marks as follows to Max 6: 1 Function heading and ending including parameter and return value
2. [6] (a) 2 Declaration and initialisation (to 1) of local Integer Value for result
3. [6] (a) 3 Check for illegal value (< 0)
4. [6] (a) 4 (Conditional) loop while ThisNum not zero // loop for ThisNum iterations
5. [6] (a) 5 Attempt to form answer by successive multiplication
6. [6] (a) 6 Completely correct MP5
7. [6] (a) 7 Return INTEGER value correctly in both cases: ThisNum < 0 and >= 0
8. [6] (a) ALTERNATIVE RECURSIVE SOLUTION: 1 Function heading and ending including parameter and return value
9. [6] (a) 2 Test for ThisNum > 1 and if so return product of Thisnum and Factorial(ThisNum-1)
10. [6] (a) 3 Check for special case...
11. [6] (a) 4 ...return 1 for 0 and 1 and return -1 for negative values
12. [6] (a) 5 Return INTEGER value (correctly in all cases)
13. [4] (b) One mark for: Rows A, B AND C
14. [4] (b) Each of rows D, E and F
15. [4] (b) A: Is Num > 9?
16. [4] (b) B: YES
17. [4] (b) C: NO
18. [4] (b) D: Set <Identifier> to Factorial (Num)
19. [4] (b) E: OUTPUT "Factorial of ", Num, " is ", <Identifier>
20. [4] (b) F: Set Num to Num + 1 // Increment Num