9608_s18_qp_32
A paper of Computer Science, 9608
Questions:
6
Year:
2018
Paper:
3
Variant:
2
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1
Data types can be defined in a programming language. The data type, StudentRecord, is defined by the code: TYPE StudentRecord DECLARE StudentID : INTEGER DECLARE StudentFirstName : STRING DECLARE StudentSurname : STRING DECLARE StudentDOB : DATE DECLARE StudentCourse : ARRAY[1:10] OF STRING ENDTYPE A variable, CollegeStudent, is declared with the code: DECLARE CollegeStudent : StudentRecord Write a pseudocode statement to assign 6539 to the StudentID of CollegeStudent. The type definition for StudentRecord is changed. Students can take six courses from: Computer Science, Engineering, Science, Maths, Physics, Chemistry, Music, Drama and English Language. Rewrite one line from the type definition of StudentRecord to implement the change. DECLARE The values for the field StudentID must be between 1 and 8000 inclusive. Rewrite one line from the type definition of StudentRecord to implement the change. DECLARE A programmer is asked to write a program to process the assessment data for each student. Students sit one exam in every course they take. A composite data type, StudentAssessment, needs to be defined with the following three fields. • a student assessment code (a unique code of three letters and two digits) • the marks for the six exams • the average mark of the six exams Write pseudocode to define the data type StudentAssessment. Data about all students and their assessments are stored in a file that uses random organisation. The StudentID is used as the key field. The program allows a user to enter data for a new student. Explain how the program adds the new data to the file.
4. Further Problem-solving and Programming Skills  →  4.1. Computational thinking and problem-solving
3. Advanced Theory  →  3.1. Data representation
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2
The following syntax diagrams show the syntax of: • an assignment statement • a variable • an unsigned integer • a letter • a digit • an operator A B C + ; = - * / letter digit operator unsigned integer variable assignment statement variable letter digit unsigned integer variable variable operator The following assignment statements are invalid. Give the reason in each case. A = B + 5; Reason A = B − D; Reason C4 = B2 − A1 + C3; Reason Complete the Backus-Naur Form (BNF) for the syntax diagrams shown on the opposite page. ::= ::= ::= ::= The syntax of variable is changed to allow one or more letters followed by an unsigned integer. Draw a syntax diagram for the new syntax of the variable.
3. Advanced Theory  →  3.4. System software
2. Fundamental Problem-solving and Programming Skills  →  2.3. Programming
1. Theory Fundamentals  →  1.1. Information representation
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3
In a computer system, real numbers are stored using normalised-floating point representation with: • 8 bits for the mantissa • 4 bits for the exponent • two’s complement form for both mantissa and exponent. Calculate the normalised floating-point representation of + 21.75 in this system. Show your working. Working Mantissa Exponent Find the denary value for the following binary floating-point number. Mantissa Exponent Show your working. Working Answer
3. Advanced Theory  →  3.1. Data representation
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4
The TCP/IP protocol suite is used on the Internet. The table has statements about transmitting data across the Internet. Put a tick (✓) in each row to identify whether the responsibility belongs to TCP or IP. Responsibility TCP IP Correct routing Host to host communication Communication between networks Retransmitting missing packets Reassembling packets into the correct order Identify two other internet protocols. State a use for each protocol. Protocol 1 Use Protocol 2 Use State the name of the TCP/IP layer that uses IP addresses. Emails are transmitted across the Internet using packet switching and routing tables. Give four items of data in an IP data packet. Describe two benefits of using packet switching. Benefit 1 Benefit 2 Give two items of data stored in a routing table.
3. Advanced Theory  →  3.2. Communication and Internet technologies
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5
Katarina works for a company specialising in the sale of computer parts and accessories. She works in the London office and her colleague Lucy works in the Hong Kong office. Katarina emails confidential information to Lucy so that only Lucy can read the information. Explain how public and private keys are used to ensure that only Lucy has a readable copy of the confidential information. Julio is buying items from the online shop. He already has an account with the shop. Explain how the use of Secure Socket Layer (SSL) or Transport Layer Security (TLS) helps to keep Julio’s confidential information secure. The manager of the company is concerned about the threat of malware. State three vulnerabilities that a malware can exploit.
3. Advanced Theory  →  3.5. Security
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6
There are five scenarios on the left and two types of system on the right. Draw a line to link each scenario to its correct type of system. System Control Monitoring Scenario Car speed display Aeroplane autopilot Rollercoaster Recording the rainfall at a weather station Robot loading a part onto a conveyor belt Mary has six fish tanks. The temperature of the water in each tank needs to be within a specific range. Identify three items of hardware that Mary can add to her tanks to help maintain the temperature. Describe the purpose of each item. Item 1 Purpose Item 2 Purpose Item 3 Purpose A temperature reading is taken from each tank once per minute. The temperature reading is stored as two successive bytes. The format is shown: Fish tank Temperature reading Byte 1 Byte 2 The fish tank number is indicated by setting one of the bits in Byte 1 to 1. For example, fish tank number 5 is indicated by setting bit 5 to 1. Bit 7 of Byte 1 is a flag: • the flag’s initial value is zero • when the reading has been processed, the flag’s value is set to 1 Bit 0 of Byte 1 is unused. Byte 2 contains the temperature reading as a two’s complement integer. After a temperature reading has been taken, the bytes contain the following data. Byte 1 Byte 2 Analyse the data contained in the two bytes. The system receives a temperature reading of − 2 from fish tank number 4. Complete the bytes to show the values for this reading after it has been processed. Byte 1 Byte 2 A hardware device to affect the temperature of each tank is on or off depending on the value of a bit in memory location 6753. If bit 4 is 1, then the hardware device in fish tank 4 is on. Write assembly language instructions to set bit 4 of memory location 6753 to 1 without changing any other bits. Use the instruction set provided. Instruction set Instruction Explanation Op code Operand LDD Direct addressing. Load the contents of the location at the given address to ACC. STO Store the contents of ACC at the given address. AND #n Bitwise AND operation of the contents of ACC with the operand. AND Bitwise AND operation of the contents of ACC with the contents of . XOR #n Bitwise XOR operation of the contents of ACC with the operand. OR #n Bitwise OR operation of the contents of ACC with the operand. OR Bitwise OR operation of the contents of ACC with the contents of . can be an absolute address or a symbolic address.
3. Advanced Theory  →  3.6. Monitoring and control systems
1. Theory Fundamentals  →  1.4. Processor fundamentals
1. Theory Fundamentals  →  1.1. Information representation
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