2021 NASS Computing P1 Solutions

Sec 4E Prelim P1 Ans 1 (a) Answer [4] Term Description Solid-state hard disk Optical disc Read-only memory Data that is stored is volatile and can be quickly accessed by the processor when needed. Data is stored on a magnetic material that can be read or written by a magnetic “head”. Data is stored as very small pits or indentations that can be read or written by a laser Data is stored in electronic circuits called “flash memory” that have no moving parts. Data that is stored rarely has need for change or would be needed for a computer to start up. Data is stored in a square plastic enclosure composed of a thin and flexible disk of a magnetic storage medium with a fabric that removes dust particles from the spinning disk Magnetic hard disk

1 (b) The central processing unit acts like the “brain” of a computer system. It contains the circuitry to interpret and execute program instructions. The arithmetic logic unit does all mathematical operations and logical calculations. Some computers have two such units to process two calculations simultaneously. That is called dual core technology. These units are also accompanied by several small data storage units called processor registers. The control unit receives orders from random access memory in the form of instruction and decode that instruction down into specific commands for other components inside computer system. It directs the data flow and how data should be stored, transmitted and received from different parts of the computer. [4] 2 (a) Module 1: character name and gender creation Module 2: character movement Module 3: shop furniture placement. Module 4: customer orders Or other logical modules that help to run the game. [4] (b) Input(s): price: float value of each item sold, time: timing which item is served Output(s): total_earnings: total amount of money earned Process required: if time is less then 30 seconds, add price x 1.2 to total_earnings. Else, add price to total_earnings. [4] (ci) valid_name is a variable as it can hold two different values. [1] (cii) Range check and format check Do not accept presence check. [2] (ciii) Boundary condition: “Dan” or “ “aaaaaaaaaaaaaaa” (inputs with 3 or 15 letters.) Error condition: “Dan56” or “Da” (inputs which trigger the checks for range and format) [4] 3 (ai) (1101001)2 [1] (aii) 107

(bi) 1000 1001 1100 1111 1111 0000 [1] (bii) (FE)16 [1] (biii) Network addresses ASCII codes Memory dump Any two [2] 4 (a) A worm is a computer program that runs automatically and attempts to spread by sending copies of itself to other computers in the network. Unlike a virus, a worm does not need to attach itself to an existing program. [2] (b) In a ransomware attack, the perpetrator extorts from the user financially and threatens to prevent the user from recovering his/her files if he/she does not comply. [1] (c) 1. Update Software Regularly as worms run automatically and do not require human interaction