JYSS 4E_COM_Prelim_P1_MS

Mark Scheme – 2022 Sec 4E Computing Prelim Paper 1 Qn Answer Marks 1a 1 m for name, 1 m for function 1ai ALU – Arithmetic Logic Unit Processes data by performing basic mathematical and logical operations such as addition, subtraction, multiplication and division. This unit performs the actual work of performing calculations and transforming data. 2 1aii CU – Control unit Follows instructions and decides when data should be stored, received or transmitted by different parts of the computer (including the ALU). This unit makes sure that data is transported to where it needs to be, and that it is processed in the correct order. 2 1b 1 m for working, 1 m for answer 1bi 12410 = 7C16 124 / 16 = 7 R 12 2 1bii 11012 = D16 23 + 22 + 1 = 1310 2 1biii 17716 = 375 162 + 7(16) + 7 2 10 Qn Answer Marks 2a 1m for each correct line Term Description Device that connects multiple LANs that uses the same protocol Media Access Control (MAC) address A 32-byte string that identifies a wireless access point (WAP) and all the devices connected to it. Server Used together with an Internet Protocol (IP) address to identify a program running on a network Port number Hardware interface to enable the transfer of data between a device and network Ethernet Computer that shares resources with and responds to requests on the network Network Interface Controller Sequence of bytes (usually permanent in nature) that is used to identify a particular physical network device. The most commonly used wired network protocol for local and metropolitan area networks. 5

2 Qn Answer Marks 3ai 0 1 1 1 1 0 1 1 1 3aii A checksum is a calculated value that is used to determine the integrity of transmitted data. The data and the checksum are sent together. At t he destination, the checksum is recalculated and compared to the sent checksum value . If the checksum value of the received data matches the sent checksum value, the data was transmitted correctly. If they differ, an error has occurred. 3 3bi Star 1 3bii 1 m for each reason, any two 2 Due to data confidentiality,  Data and resources are shared using one or more dedicated servers; each computer has a distinct role – client or server  High security as access rights can be controlled centrally at a server  Centralised and carried out only at the server; usually managed by a network administrator 7 Qn Answer Marks 4 1 m for each blank Access control or authorization is the ability of a computer to control the access of data and resources by an authenticated user. Below are three ways computers provide access control. Most operating systems can control the ability of users to view or make changes to specific files or folders by setting file permissions . However, these settings do not prevent unauthorized physical access to the storage device. To prevent this, it