9608_s17_qp_32
A paper of Computer Science, 9608
Questions:
6
Year:
2017
Paper:
3
Variant:
2
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1
Consider the following pseudocode user-defined data type: TYPE MyContactDetail DECLARE Name : STRING DECLARE HouseNumber : INTEGER ENDTYPE Write a pseudocode statement to declare a variable, NewFriend, of type MyContactDetail. Write a pseudocode statement that assigns 129 to the HouseNumber of NewFriend. The user-defined data type MyContactDetail needs to be modified by: • adding a field called Area which can take three values, uptown, downtown or midtown • amending the field HouseNumber so that house numbers can only be in the range 1 to 499. Write the updated version of MyContactDetail. A pointer is a variable that stores the address of a variable of a particular type. Consider the pseudocode on page 3, which uses the following identifiers: Identifier Data type Description IPointer ^INTEGER pointer to an integer Sum INTEGER an integer variable MyInt1 INTEGER an integer variable MyInt2 INTEGER an integer variable Sum // assigns the value 91 to the integer variable Sum IPointer @Sum // assigns to IPointer the address of the // integer variable Sum MyInt1 IPointer^ // assigns to variable MyInt1 the value at an // address pointed at by IPointer IPointer^ MyInt2 // assigns the value in the variable MyInt2 to // the memory location pointed at by IPointer The four assignment statements are executed. The diagram shows the memory contents after execution. Variable Memory Address Contents . . . IPointer . . . Sum . . . MyInt1 MyInt2 . . . Use the diagram to state the current values of the following expressions: IPointer IPointer^ @MyInt1 IPointer^ = MyInt2 Write pseudocode statements that will achieve the following: Place the address of MyInt2 in IPointer. Assign the value 33 to the variable MyInt1. Copy the value in MyInt2 into the memory location currently pointed at by IPointer.
2. Fundamental Problem-solving and Programming Skills  →  2.3. Programming
2. Fundamental Problem-solving and Programming Skills  →  2.2. Data representation
1. Theory Fundamentals  →  1.4. Processor fundamentals
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2
The following incomplete table shows descriptions and terms relating to malware. Complete the table with appropriate description and terms. Description Term Malicious code is installed on a personal computer so that the user is misdirected to a fraudulent web site without their knowledge. An attempt to acquire sensitive information, often for malicious reasons, by trying to deceive the user through the contents of an email. Worm State two vulnerabilities that the malware in part or part can exploit. Vulnerability 1 Vulnerability 2 Digital certificates are used in internet communications. A Certificate Authority (CA) is responsible for issuing a digital certificate. The digital certificate contains a digital signature produced by the CA. Name three additional data items present in a digital certificate. Describe how the digital signature is produced by the CA. Give the reason for including a digital signature in the digital certificate.
3. Advanced Theory  →  3.5. Security
Open
3
A logic circuit is shown: Q R S P Write the Boolean algebraic expression corresponding to this logic circuit: S = Complete the truth table for this logic circuit: P Q R Working space S Complete the Karnaugh Map (K-map) for the truth table in part . PQ R The K-map can be used to simplify the function in part . Draw looparound appropriate groups to produce an optimal sum-of-products. Write a simplified sum-of-products expression, using your answer to part . S = One Boolean identity is: (A + B) . C = A . C + B . C Simplify the expression for S in part to the expression for S in part . You should use the given identity and De Morgan’s Laws.
3. Advanced Theory  →  3.3. Hardware
1. Theory Fundamentals  →  1.3. Hardware
Open
4
Three file organisation methods and two file access methods are shown below. Draw lines to link each file organisation method to its appropriate file access method. File organisation method File access method random sequential serial direct sequential An energy company supplies electricity to a large number of customers. Each customer has a meter that records the amount of electricity used. Customers submit meter readings using their online account. The company’s computer system stores data about its customers. This data includes: • account number • personal data (name, address, telephone number) • meter readings • username and encrypted password. The computer system uses three files: File Content Use A Account number and meter readings for the current month. Each time a customer submits their reading, a new record is added to the file. B Customer’s personal data. At the end of the month to create a statement that shows the electricity supplied and the total cost. C Usernames and encrypted passwords. When customers log in to their accounts to submit meter readings. For each of the files A, B and C, state an appropriate file organisation method for the use given in the table. All three file organisation methods must be different. Justify your choice. File A organisation Justification File B organisation Justification File C organisation Justification
3. Advanced Theory  →  3.1. Data representation
Open
5
The TCP/IP protocol suite can be viewed as a stack with four layers. Complete the stack by inserting the names of the three missing layers. Application layer BitTorrent is a protocol used at the Application layer for the exchange of data. State the network model used with this protocol. State the use of BitTorrent. Explain how the exchange of data is achieved using BitTorrent. State two additional protocols that are also used at the Application layer for the exchange of data. For each protocol, give an example of an appropriate exchange of data. Protocol 1 Example Protocol 2 Example
3. Advanced Theory  →  3.2. Communication and Internet technologies
Open
6
A large office building has many floors. On each floor there are security sensors and security cameras. There is the same number of sensors on each floor. The building has a single security room. The images from the security cameras are output on monitors (one monitor for each floor) placed in the security room. The data from the sensors are read and processed by a computer system. Sensor readings and warning messages can be displayed on the monitors. State the name given to the type of system described. Explain your answer to part . State two sensors that could be used in this system. Sensor 1 Sensor 2 A software routine: • checks the readings from the sensors • outputs readings and warning messages to the monitors • loops continuously. The routine uses the following pseudocode variables: Identifier Data type Description FloorCounter INTEGER Loop counter for number of floors SensorCounter INTEGER Loop counter for number of sensors NumberOfFloors INTEGER Stores the number of floors NumberOfSensors INTEGER Stores the number of sensors ForEver BOOLEAN Stores value that ensures continuous loop Complete the following pseudocode algorithm for the routine. 01 ForEver 02 REPEAT 03 FOR FloorCounter 1 TO NumberOfFloors 04 FOR SensorCounter 1 TO 05 READ Sensor(SensorCounter)on Floor(FloorCounter) 06 IF Sensor value outside range 07 THEN 08 OUTPUT “Problem on Floor ”, FloorCounter 09 ENDIF 10 ENDFOR 11 ENDFOR 12 // 13 // Delay loop 14 // Delay loop 15 // 16 UNTIL A delay needs to be introduced before the loop is processed again. Write a FOR loop, in pseudocode, to replace lines 13 and 14. Give a reason for this delay in the system. An alternative method of reading and processing sensor data is to use interrupts. Each sensor is connected so that it can send an interrupt signal to the processor if its value changes. On receipt of an interrupt signal, the processor carries out a number of steps as shown in the following diagram. Interrupt 1. Disable interrupts Return to task 6. Enable interrupts 2. Save current task 3. Identify source of interrupt 4. Jump to Interrupt Service Routine 5. Restore task State the purpose of step 3. Explain what happens at step 4.
2. Fundamental Problem-solving and Programming Skills  →  2.1. Algorithm design and problem-solving
Open