9608_w19_qp_33
A paper of Computer Science, 9608
Questions:
9
Year:
2019
Paper:
3
Variant:
3
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1
Real numbers are stored using floating-point representation in a computer system. This representation uses: • 8 bits for the mantissa, followed by • 4 bits for the exponent. Two’s complement form is used for both the mantissa and the exponent. A real number is stored as a 12-bit normalised binary number as follows: Mantissa Exponent Calculate the denary value for this binary number. Show your working. Working Denary value Calculate the normalised binary number for −3.75. Show your working. Mantissa Exponent Working The number of bits available to represent a real number is increased to 16. State the effect of increasing the size of the exponent by 4 bits. State why some binary representations can lead to rounding errors. Complete the following descriptions by inserting the two missing terms. can occur in the exponent of a floating-point number, when the exponent has become too large to be represented using the number of bits available. A calculation results in a number so small that it cannot be represented by the number of bits available. This is called .
3. Advanced Theory  →  3.1. Data representation
1. Theory Fundamentals  →  1.1. Information representation
Open
2
The following syntax diagrams for a programming language show the syntax of: • a condition • a variable • a number • a letter • a digit • an operator digit == > Reason abc := cba Reason bc Complete the Backus-Naur Form (BNF) for the syntax diagram. ::= ::= ::= ::=
3. Advanced Theory  →  3.4. System software
4. Further Problem-solving and Programming Skills  →  4.1. Computational thinking and problem-solving
2. Fundamental Problem-solving and Programming Skills  →  2.3. Programming
Open
4
A Boolean expression produces the following truth table. INPUT OUTPUT A B C X Write the Boolean expression for the truth table as a sum-of-products. X = Complete the Karnaugh Map (K-map) for the truth table above. AB C The K-map can be used to simplify the expression in part . Draw loops around appropriate groups in the K-map in part to produce an optimal sum-of- products. Write, using your answer to part , a simplified sum-of-products expression for the truth table. X =
3. Advanced Theory  →  3.3. Hardware
1. Theory Fundamentals  →  1.3. Hardware
Open
5
Explain why user-defined data types are necessary. An organisation stores data about its employees. • Employee ID is a five-digit number, for example, 01234. • Employee name is a string, for example, ‘Kiri Moana’. • Department is one of three values: Sales, Technical, Customer services. • Salary is an integer value in the range 25 000 to 150 000. Complete the following pseudocode definition of a user-defined data type to store the employee data. TYPE Employee DECLARE EmployeeID : DECLARE EmployeeName : STRING DECLARE Department : ( ) DECLARE Salary : 25000 150000 Write a pseudocode statement to declare a variable, NewEmployee of data type Employee. Write a pseudocode statement that assigns 02244 to the EmployeeID of NewEmployee. Employee is an example of a record that is a composite data type. State two other composite data types.
3. Advanced Theory  →  3.1. Data representation
Open
6
An operating system (OS) uses a memory management technique called paging. Explain what is meant by the following terms. Page Page frame Page table Explain why an operating system needs to use scheduling algorithms. State what is meant by an interrupt. For a computer system using multi-programming, the low-level scheduler decides which process will get next use of the processor. One algorithm could be a round-robin, which means every process gets use of the processor in sequence for a fixed amount of time (time-slice). For a round-robin algorithm, five processes are currently loaded and get the use of the processor in the sequence: JOB21 – JOBSS – JOBPT – JOB32 – JOB42, then return to JOB21 Process JOB32 has just completed its time-slice. The following paragraph describes what happens next. Complete the paragraph by inserting the missing processes. Interrupt received from the low-level scheduler. Save all register contents for . Copy the saved registers for to the CPU. The processor will now process .
3. Advanced Theory  →  3.4. System software
1. Theory Fundamentals  →  1.4. Processor fundamentals
Open
8
Digital certificates are used in internet communications. A Certificate Authority (CA) is responsible for issuing a digital certificate. Identify two data items present in a digital certificate. The following paragraph describes how a digital signature is produced. Complete the paragraph by inserting an appropriate term in each space. A algorithm is used to generate a message digest from the plain text message. The message digest is with the sender’s .
3. Advanced Theory  →  3.5. Security
Open
9
The following incomplete table shows descriptions relating to computer architectures. Complete the table by inserting the appropriate terms. Description Term A • There are several processors. • Each processor executes different sets of instructions on one set of data at the same time. B • The processor has several ALUs. • Each ALU executes the same set of instructions on different sets of data at the same time. C • There is only one processor. • The processor executes one set of instructions on one set of data. D • There are several processors. • Each processor executes a different set of instructions. • Each processor operates on different sets of data. State three characteristics of massively parallel computers.
1. Theory Fundamentals  →  1.4. Processor fundamentals
3. Advanced Theory  →  3.3. Hardware
Open