2021 TSS Computng P1 Solutions

2021 Computing Prelim Paper 1 – Marking Scheme Question Answer Marks 1(a) One mark each: B1 – Currency B2 – Percentage Not accepted: Accounting, Numbers 2 1(b) PMT() 1 1(c) IPMT() 1 1(d) One mark each: =ROUND(B4,0) -$1,012 =CEILING(B8,-10) -$680 =SUM(B8:B247) -$200,000 =LARGE(C8:C247,2) -$3.36 Note: Negative sign (-) and dollar sign ($) must be written. 4 1(e) One mark for function name, one mark for correct parameters =COUNTIF(C8:C247, "<-100") 2 1(f) FV() 1 Sub Total 11 Question Answer Marks 2(a) One mark for the correct answer and one mark for showing relevant working: Sum of place values method: 110010012 = 27 + 26 + 23 + 20 = 20110 2

2(b) One mark for the correct answer and one mark for showing relevant working: Sum of place values method: 27 26 25 24 23 22 21 20 128 64 32 16 8 4 2 1 1 0 0 1 0 1 0 0 ∴ 14810 = 1001 01002 OR Division by 2 method: Denary Quotient Remainder 148 74 0 74 37 0 37 18 1 18 9 0 9 4 1 4 2 0 2 1 0 1 0 1 ∴ 14810 = 1001 01002 2 2(c) A16 = 10102 E16 = 11102 ∴ AE16 = 1010 11102 1 2(d) Any two from: Hexadecimal numbers are more compact than binary numbers (Fewer number of digits used to represent a value in hexadecimal as compared to binary) It is easier to identify values/spot errors in hexadecimal numbers as compared to binary numbers. It is easy to convert between hexadecimal numbers and binary numbers if required. 2 2(e)(i) A byte is a unit of data (or memory) that is made up of eight bits. 1 2(e)(ii) 32KB = 32 x 103 x 8 b = 256 000 b 1 2(e)(iii) 4GiB = 4 x (1024)4 B = 4 294 967 296 B 1 Sub Total 10

Question Answer Marks 3(a) One mark for each part: Weak authentication methods: Example: Customers are allowed to use short passwords/ passwords which could be guessed by others, e.g. name, date of birth. OR Internet banking login page that allows multiple attempts to login by malicious user / does not differentiate between human and robot user. Measure: Implement strong password policies (e.g. minimum password length, use of special characters) / use two-factor authentication such as security tokens, SMS one-time pin (OTP) or biometrics OR Limit the number of incorrect attempts before the account will be locked / ask security questions to verify that the user is not a robot. 2 3(b) One mark for each part: Poor access controls: Example: Bank employees who are unauthorised to access customer’s data may be able to view or change their account information without permission. OR Internet banking page showing too much unnecessary information after customer has logged in, e.g. full credit card number, date of birth, address (This is risky when third-party is able to view the customer’s screen, e.g. spyware on customer’s PC, accessing through public wifi, etc.) OR Customers are allowed to perform large transactions or change critical