XMSS 2018 P1 Solution

1 4E Prelim Computing Paper 1 2018 1 A computer processor carries out the instructions in a computer program. The memory is where data and instructions are stored ready to be processed. The address bus identifies the location of data. The data bus transports the data from one location to another. [5] Total [5] 2 Volatile data storage: Processor register, RAM (any one) Non-volatile data storage: ROM, Any external storage (any one) [2] Total [2] 3 Inputs: - 24 student names - 24 marks for Physics Outputs: - Name of the student with the lowest score - score for that student Processes required: - Store input data in arrays/lists - Search for the student with the lowest mark/sort the arrays in mark order [6] Total [6] 4 Step 1: If Number is less than Divisor, proceed to Step 3. Otherwise, proceed to Step 2. Step 2: Subtract Divisor from Number and then proceed to Step 1. Step 3: Output Number as the final answer. [3] Total [3]

2 5 num sum n rem OUTPUT 371 0 371 1 1 37 7 344 3 3 371 0 TRUE [5] Total [5] 6 a constant: A name with an associated value that usually cannot be changed while the program is running. a variable: A name with an associated value that can be changed while the program is running. an array: Sequence where all the items have the same size and are arranged consecutively in memory. [1] [1] [1] Total [3] 7 a = int(input("Please enter an integer: ")) b = int(input("Please enter another integer: ")) total = a + b if a == b: print("Twice the sum:", 2*total) else: print("Sum:", total) [9] Total [9] 8 length check: Process of ensuring that input data is not too long or too short. range check: Process of ensuring that input data is within the required range of values. [1] [1] Total [2]

3 9 Error 1: Total = 500 Correction: Total = 0 Error 2: WHILE Counter > 11 DO Correction: WHILE Counter < 11 DO Error 3: Total = Total – Number[Counter] Correction: Total = Total + Number[Counter] Error 4: Average = Total / Counter Correction: Average = Total / 10 [1] [1] [1] [1] [1] [1] [1] [1] Total [8] 10 [5] Total [5] 11a B16 = 1110 = 10112 C16 = 1210 = 11002 Binary number = 1011 1100

4 11b 200R1 100R0 50R0 25R0 12R1 6R0 3R0 1R1 0R1 Binary number = 110010001 11c 687R9 42RF 2RA 0R2 Hexadecimal number = 2AF9 Total [6] 12 [6] Total [6] 24 0 1=22 0 0=21 0 0=25 0=22 5=21 2=26=23=21=16 11001=16 687=16 42=16 2=

5 13a =B5/C5 [1] 13b = (D2 + D3 + D4 + D5 + D6)/5 OR = AVERAGE(D2:D6) OR = SUM(D2:D6)/5 [1] 13c [4] Total [6] 14a A network allows a group of computers to make use of shared resources such as printers or files. Depending on the network’s configuration, every user who logs on to the network may have access to the Internet. Software can be stored on the central server of a network and deployed to other computers over a network. Data files can be stored on a central server for ease of access and backup purposes. Computers in the same network are often able to share instant messages and emails for communication. [2] 14b - counts the number of ones in each byte of data - parity bit is set so there are an even/odd number of ones before the data is transmitted. - If the number of ones is not even/odd when the data has been transmitted - then an error has occurred [4] Total [6]

6 15 Flowchart [8] *Refer to pseudo-code marks allocation. START number = [] negative = 0 positive = 0 index = 0 Is index < 20? INPUT number[index] Is number[index] < 50? OUTPUT index Is number[index] < 0? positive = positive + 1 negative = negative + 1 OUTPUT negative OUTPUT positive END Yes Yes No Yes No index = index + 1 No

7 15 Pseudo-code number = [] negative = 0 positive = 0 index = 0 WHILE index < 20 INPUT number[index] IF number[index] < 50 OUTPUT index ENDIF IF number[index] < 0 negative = negative + 1 ELSE positive = positive + 1 ENDIF index = index + 1 ENDWHILE OUTPUT “Number of negative numbers: “ + negative OUTPUT “Number of positive numbers: “ + positive [8] Total [8]