SPSS 2018 P1 Solution

Sec 4 Prelims 2018 P1 Marking Scheme 1 Function Description MAX Returns the most frequently occurring or repeated value in the given numbers or the given range/cell references LARGE Returns a user-defined number of characters starting from a position of the text value text MODE.SNGL Returns the largest number out of the given numbers or the numbers in the given range/cell references Returns the kth largest number in a range of cells 2a 182 , correct working 2b 11110101, correct working 2c 22, correct working 3 Processor registers ALU / control unit control unit / ALU RAM ROM Secondary storage 4a Data bus Any two of the following: • Carries / transports data / example of data ... • … that is currently being processed / that will be / has been processed • Data can travel in both directions (bidirectional) 4b Address bus Any two of the following: • Carries / transports an address / location … • … of the next item to be fetched • Data travels one way (unidirectional)

5a Language designed for humans to communicate instructions to computers 5b *Compiler / #Interpreter 5c Based on 5b’s answer: *Compiler translates source code into machine code completely before running the compiled program #Interpreter translates source code into machine code while the interpreted program is running 5d Based on 5b’s answer: *Programs run at a faster speed because all the translation has been done beforehand / Compiler is not needed to run after compilation is complete / Syntax errors are detected before program is even run #Changes to the source code take effect immediately / Facilitates learning and experimentation as interpreters usually offer an interactive mode 6 Inputs: Names of 50 employees (string), Contract amount of 50 employees (float) [2 marks] Outputs: Name of the employee who secured the biggest contract and its contract amount. [2marks] Processes: Store the names with the corresponding contract amounts in an array/list. Search the list for the biggest contract amount and output the name of the employee and the contract amount. [2marks] 7 Error: count Correction: count=0 Error: PIN = PIN%10 Correction: PIN = PIN//10 or PIN = PIN/10 Error: IF PIN == 5 Correction: IF count == 5 Error: UNTIL PIN >= 1 Correction: UNTIL PIN < 1 8a Phishing It uses emails and fake websites that appear to be from reputable companies in order to steal personal information from users. 8b Any two of the following: • Email uses a generic greeting, “Dear Customer DBS”, suggesting that it was sent automatically and not by a person • Email has grammatical, spelling and punctuation errors, “verifivation”, “for your safety access has been locked”, that suggest it is not from a legitimate source • Tone of email is excessively urgent or threatening, “Thank you for your immediate attention to this matter”. • Email uses a generic sign off with no indication of the department and name of officer-in-charge of the case, “The team of DBS | Singapore” • URL is questionable as it has a pathname / filename that is a long unintelligible string of characters but most reputable sites tend to use more relevant pathnames / filenames. • The title of the email “Update Credit-card” did not match the content of

the email • There are multiple and different hyperlinks provided for the same cause • Banks would never initiate to ask for personal data through emails 9a Any two of the following: • helps prevent unauthorised access / helps prevent hacking • checks that data meets criteria / identifies when data does not meet criteria • acts as a filter for (incoming and outgoing) data / blocks any unacceptable data /allows acceptable data through 9b Any three of the following: • Encrypt the data so it cannot be understood by those not entitled to view it • Password protected / biometrics / strong authentication / 2-factor authentication to help prevent unauthorised access • Virus checking software that helps prevent data corruption or deletion / identifies / removes a virus in the system / scans a system for viruses • Spyware checking software that helps prevent data being stolen/copied/logged / scans a system for spyware • Drop-down input methods / selectable features to reduce risk of spyware / keylogging • Physical method e.g. locked doors / CCTV timeout / auto log off to help prevent unauthorised access • Network / company policies / training employees to educate users how to be vigilant • Access rights allows users access to data that they have permission to view / prevents users from accessing data that they do not have permission to view 10 Protocol to use / (access) protocol Domain name of web server / domain (name) Name or path of page to request / filename

11 i J temp num_list[j] num_list[j+1] OUTPUT 0 0 1 2 7 2 2 2 9 2 3 1 0 4 7 4 1 4 9 4 2 3 2 0 7 9 7 1 2 3 3 0 1 2 3 4 0 [9, 7, 4, 2] 12 0, 0,0,1. AND gate

13a X = (A AND NOT B) OR (B AND NOT C) 13b 14a Local Area Network (LAN), Metropolitan Area Network (MAN), Wide Area Network (WAN) 14bi Any two of the following: • High mobility as users can move about freely within the range of the wireless network • Easier to add new devices to the network as router can be easily configured • More organized without the mess of cables 14bii Any one of the following: • Wired transmission is more reliable and unaffected by interference • Wired transmission is more secure and less susceptible to interception and hacking • Wired transmission is usually faster and higher bandwidth as cables provide dedicated connection • Lower cost as equipment and cables are cheap 14c Any two of the following: • In a client-server network, one or more higher capacity computers will act as servers while remaining computers are clients, but in a P2P network all computers are able to act as clients and servers. • In a client-server network, each server contains data and other resources to be shared with clients, but in a P2P network users are able to share files and resources located on their computer and access that found on other computers in the network. • In a client-server network, there can be high security as the server can control access rights centrally, but in a P2P network, security is low as individual computers are required to handle the security. • In a client-server network, bandwidth is typically high but limited by the capability of the server, but in a P2P network, bandwidth varies

depending on size of request and whether the request can be divided into smaller requests to be handled by multiple computers simultaneously. 15 Suggested Solution (Pseudo-code) word_list = [] counter = 0 num_smaller_than_4 = 0 num_bigger_than_4 = 0 WHILE counter < 20 DO INPUT word word_list[counter] = word IF length of word < 4 THEN num_smaller_than_4 = num_smaller_than_4 + 1 ELSE IF length of word > 4 THEN num_bigger_than_4 = num_bigger_than_4 + 1 ELSE OUTPUT counter ENDIF ENDIF ENDWHILE OUTPUT num_smaller_than_4 OUTPUT num_bigger_than_4 Any eight of the following: • Initialization of 3 variables word_list (array), num_smaller_than_4, num_bigger_than_4 • Loop management 20 repetitions • Input word (at each iteration of loop) • Store word in word_list (array) • Checking if word length is lesser than 4 … • Checking if word length is greater than 4 … • … update num_smaller_than_4 / num_bigger_than_4 • Checking if word length equals 4 • … outputs the list (array) index • Outputs num_smaller_than_4, num_bigger_than_4