9608_w21_qp_32
A paper of Computer Science, 9608
Questions:
8
Year:
2021
Paper:
3
Variant:
2
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1
Data types can be defined using pseudocode. The data type, BicycleRecord, is defined in pseudocode as: TYPE BicycleRecord DECLARE BicycleID : INTEGER DECLARE BicycleAvailable : BOOLEAN DECLARE BicycleLocation : (RiverSide, BusStation, TrainStation, TownSquare, Library) DECLARE DateChecked : DATE ENDTYPE A variable, LoanBicycle, is declared in pseudocode as: DECLARE LoanBicycle : BicycleRecord Write pseudocode statements to assign 567 to the BicycleID of LoanBicycle and FALSE to the BicycleAvailable of LoanBicycle. The type definition for BicycleRecord is changed. The definition has been extended to include borrower identification numbers, BorrowerID, for the last 10 people who borrowed a bicycle. Each identification number is an integer. Write the pseudocode statement needed in the type definition of BicycleRecord. The values for the field BicycleID must be between 500 and 599 inclusive. Rewrite one pseudocode line from the type definition of BicycleRecord to implement the change. Data about all the bicycles are stored in a file that uses random file organisation. BicycleID is used as the key field. Explain how a program could add an extra record to this file.
3. Advanced Theory  →  3.1. Data representation
4. Further Problem-solving and Programming Skills  →  4.3. Further programming
Open
3
The truth table for a logic circuit with four inputs is shown. INPUT OUTPUT P Q R S X Write the Boolean algebraic expression for the truth table as a sum-of-products. X = Complete the following Karnaugh Map (K-map) for the truth table. PQ RS The K-map can be used to simplify the expression in part . Draw looparound appropriate groups in the K-map to produce an optimal sum-of-products. Write the simplified sum-of-products from the K-map. X = Simplify the expression for X, represented by the truth table in part , using Boolean Algebra.
3. Advanced Theory  →  3.3. Hardware
1. Theory Fundamentals  →  1.3. Hardware
Open
5
Flora has written a program that uses the variables p, q, r and s. Part of the program contains the following calculations: p = 5 q = 4 r = 1 s = p * (p - q + r) Write the Reverse Polish Notation (RPN) for the expression: p * (p - q + r) Show the changing contents of the stack as the value for s is calculated from the RPN expression. Convert this RPN expression back to its original infix form. p q * p q r + - + p / Syntax analysis is one stage of the compilation of a program. Identify and describe two other stages of compilation. Stage 1 Description Stage 2 Description
3. Advanced Theory  →  3.4. System software
2. Fundamental Problem-solving and Programming Skills  →  2.3. Programming
Open
6
Lara wants to send an important message to her bank over the Internet. Explain why the bank requires a digital signature for the message. Asymmetric key cryptography is used to keep Lara’s message secure during transmission over the Internet. Describe this process of encrypting and decrypting Lara’s message. Lara has received an email message that appears to be from her bank. She is not sure whether it is authentic. State two problems that could occur if Lara opens and responds to this suspicious email message.
3. Advanced Theory  →  3.5. Security
Open
8
A large car park has 6 floors. There is a large screen at the entrance to the car park. This screen displays the number of empty parking spaces on each floor. • There are 256 parking spaces for cars on each floor. • Each parking space has a sensor that detects if a car is parked on it. • Data from the sensors are read and processed by a computer system. Identify the type of system described. Justify your answer to part . Identify two types of sensor that could be used by this system. Sensor 1 Sensor 2 A program regularly checks each sensor’s readings. The number of empty parking spaces is displayed on the screen for each floor. If there are no empty parking spaces on a floor, a message is displayed on the screen to show that the floor is full. The pseudocode algorithm to display this information has been written using these identifiers. Identifier Data type Description FloorNumber INTEGER Floor number SpaceNumber INTEGER Parking space number SpaceAvailable INTEGER Counts number of empty parking spaces on a floor ForEver BOOLEAN Value to ensure continuous loop The pseudocode algorithm uses the function CheckSpace(Floor, Space). This function returns TRUE if the parking space is empty and FALSE otherwise. Complete the following pseudocode algorithm to check the number of parking spaces available. 01 ForEver ………………………………………………………………………… 02 REPEAT 03 FOR FloorNumber 1 TO ………………………………………………………………………… 04 SpaceAvailable 05 FOR SpaceNumber 1 TO ………………………………………………………………………… 06 IF CheckSpace(FloorNumber, SpaceNumber) 07 THEN 08 SpaceAvailable SpaceAvailable + 1 09 ENDIF 10 ENDFOR 11 IF SpaceAvailable > ………………………………………………………………………… 12 THEN 13 OUTPUT "Floor ", …………………………………………………………………………, " empty parking spaces "………………………………………………………………………… 14 ELSE 15 OUTPUT "Floor ", …………………………………………………………………………, " full" 16 ENDIF 17 ENDFOR 19 // delay loop 20 // delay loop 21 UNTIL ………………………………………………………………………… Write a delay loop in pseudocode for lines 19 and 20 of the pseudocode algorithm. State why a delay loop is used in this system. When a car is parked in a parking space, a bit is set in the appropriate memory location. • 32 memory locations are used for each floor with address X01 to X32, where X is the number of the floor. • Each location is one byte in length to hold the data for 8 parking spaces. For example, memory location 101 is used for parking spaces 1 to 8 and memory location 102 is used for parking spaces 9 to 16. The table shows part of floor 1 with cars parked in parking spaces 4, 11, 16 and 255. Memory location Bits Parking space number 8 – 1 16 – 9 … … … … … … … … … … 256 – 249 The data in memory location 604 is shown. State what this data represents. Explain the way in which the parking space 254 on floor 5 can be checked to see if it is empty.
2. Fundamental Problem-solving and Programming Skills  →  2.1. Algorithm design and problem-solving
Open