9608_w19_qp_32
A paper of Computer Science, 9608
Questions:
8
Year:
2019
Paper:
3
Variant:
2
Login to start this paper & get access to powerful tools
1
The following incomplete table shows descriptions relating to the security of data transmission. Complete the table with the appropriate terms. Description Term A The original data to be transmitted as a message B An electronic document from a trusted authority that ensures authentication C An encryption method produced by a trusted authority that can be used by anyone Explain the purpose of a digital signature. Describe how a digital signature is produced for transmission with the message.
1. Theory Fundamentals  →  1.6. Security, privacy and data integrity
3. Advanced Theory  →  3.5. Security
Open
2
A Boolean expression produces the following truth table. INPUT OUTPUT A B C X Write the Boolean expression for the truth table by applying the sum-of-products. X = Complete the Karnaugh Map (K-map) for the truth table in part . AB C The K-map can be used to simplify the function in part . Draw looparound appropriate groups in the table in part , to produce an optimal sum-of-products. Write, using your answer to part , a simplified Boolean expression for your Karnaugh map. X = Simplify the following expression using De Morgan’s laws. Show your working. (W + • (Y + Z)
3. Advanced Theory  →  3.3. Hardware
1. Theory Fundamentals  →  1.3. Hardware
Open
3
A computing department in a school has a Local Area Network (LAN) with a bus topology. A description of sending a message on a bus network is given. Complete the following description by inserting an appropriate term in each space. Computer 1 and Computer 2 are on the same bus network. Computer 1 sends a message to Computer 2. Before the message is sent, it is split into . Computer 1 needs to check that the is free, before sending the message, otherwise a will occur that will be managed by the protocol. The computing department’s LAN needs to connect to the Internet. Explain how each device is used in the operation of the bus network. Router Network Interface Card (NIC) The computing department’s network is being adapted to allow students to connect wireless devices. Identify two types of hardware components the computing department will need to allow wireless connection. Describe how the wireless connection sends and receives data.
3. Advanced Theory  →  3.2. Communication and Internet technologies
Open
5
A weather station uses monitoring and control systems. Describe the difference between a monitoring system and a control system. The weather station records how the outside temperature changes over a period of time. The system will read the temperature once every hour, over a period of 100 days. The temperature readings are automatically stored in a file. No other data are stored. Explain why the weather station has decided to use serial organisation for the file. Serial files can be accessed using sequential access. Explain how sequential access could be used for the temperature readings file. Name and describe a method of file organisation other than serial or sequential. Method Description
3. Advanced Theory  →  3.1. Data representation
3. Advanced Theory  →  3.6. Monitoring and control systems
Open
6
State what is meant by a user-defined data type. A pseudocode declaration for a user-defined data type for the months of the year is as follows: TYPE DECLARE Months: ( January, February, March, April, May, June, July, August, September, October, November, December) ENDTYPE Identify this type of user-defined data type. Write a pseudocode statement to declare a variable CurrentMonth of data type Months. Write a pseudocode statement to assign the value August to the variable CurrentMonth.
3. Advanced Theory  →  3.1. Data representation
2. Fundamental Problem-solving and Programming Skills  →  2.2. Data representation
Open
7
The following are the first few lines of a source code program written in a high-level language. The source code program is to be translated by the language compiler. // program written on 15 June 2019 DECLARE IsFound : Boolean; DECLARE NoOfChildren : Integer; DECLARE Count : Integer; Constant TaxRate = 15; // start of main program For Count = 1 to 50 … … … During the lexical analysis stage, the compiler will use a keyword table and a symbol table. Identify two types of data in the keyword table. Type 1 Type 2 Identify two types of data in the symbol table. Type 1 Type 2 Explain how the contents of the keyword and symbol tables are used to translate the source code program. State one additional task completed at the lexical analysis stage that does not involve the use of a keyword or a symbol table. The final stage of compilation can be code optimisation. Explain why code is optimised.
3. Advanced Theory  →  3.4. System software
2. Fundamental Problem-solving and Programming Skills  →  2.4. Software development
1. Theory Fundamentals  →  1.5. System software
Open
8
The following 16-bit binary pattern represents a floating-point number stored in two’s complement form. The twelve most significant bits are used for the mantissa and the four least significant bits are used for the exponent. Most Least significant bit significant bit Identify the binary value of the exponent. Identify the binary value of the mantissa. State whether the number stored is positive or negative. Justify your choice. Positive or negative Justification Convert the binary floating-point number in part into denary. Show your working. Working Denary value The number of bits used for the exponent is increased to eight, and the number of bits used for the mantissa is decreased to eight. State the effects of this change.
3. Advanced Theory  →  3.1. Data representation
1. Theory Fundamentals  →  1.1. Information representation
Open