SST 2019 Prelim P1 Solution

1 2019 SEC 4 PRELIMINARY EXAMINATION MARKING SCHEME Qn 1 Marking Scheme / Answer Marks (a) Data bus 1 (b) Arithmetic logic unit 1 (c) ROM 1 Qn 2 Marking Scheme / Answer Marks (a) A byte is made up on 8 bits. 1 (b) A megabyte is 1000 000 bytes. A mebibyte is 220 or 1048576 bytes. One mebibyte is 1.048576 megabytes (3 sig. fig. or more is accepted) 1 1 (c) 64 GB = 64 x 106 KB Max number of images = 64 x 106 / 500 = 128 000 1 1 Qn 3 Marking Scheme / Answer Marks (a) Number of different colours = 166 = 16777216 1 (b) (6B)16 = (10101011)2 1 (c) (D3)16 = 13 x16 + 3 x 1 = 211 1 1 Qn 4 Marking Scheme / Answer Marks Unicode is a computing industry standard for the handling of text character sets. It is used to represent a million unique characters from many different languages all over the world. Unicode uses 8 to 32 bits to represent each character. 1 1 1 Qn 5 Marking Scheme / Answer Marks (a) The size of IPv4 address is 4 bytes (32 bits) long while the size of IPv6 address is 16 bytes (128 bits) long. 2 (b) It is to increase the maximum number of IP addresses to overcome the problem of insufficient IP addresses due to increasing number of computers connected to the internet. 1 Qn 6 Marking Scheme / Answer Marks (a) Media Access Control 1 (b) They allow all devices to be uniquely identified. 1 (c) First six digits: Manufacturer’s identity number Last six digits: Device’s serial number 1 1 Qn 7 Marking Scheme / Answer Marks

2 Field Name Name of Validation Check Example of data which would fail the validation check Date of birth Format Check Alphabets involved. e.g. FIFTHJUNE Gender Presence Check Empty String is Entered Height Range Check Cannot be less than 0 metre or more than 3 m. e.g. -2, 5 e.t.c Postal code Length Check e.g. 1234, 12345678 4 marks (1 mark for each correct row. At most 1 mark for duplicate validation checks) Qn 8 Marking Scheme / Answer Marks (a) Star topology Information such as inventory needs to be centralized, so that they can be updated and shared to the various staff easily. 1 1 (b) Inputs: Items in the supermarket. Items from suppliers. Items purchased by customers Outputs: Items in the supermarket. Items from suppliers. Items purchased by customers Processes: Total number of items = Items in supermarket + Items from suppliers – Items purchased by customers 5 Qn 9 Marking Scheme / Answer Marks (a) - Use security tokens or 2FA (when making credit card payments) - Use strong passwords (to prevent unauthorized users to access online accounts). - Change passwords regularly (to prevent unauthorized users to access online accounts.) 2 (b) Understand how e-commerce sites can share your information with advertisers in their privacy policies can help you to decide whether to obtain services from these sites in the first place. 1 (c) - Lost of jobs as some traditional jobs are replaced - Lower profits for companies / shops that do not engage in e-commerce - More people ch