3.4. System software
A subsection of Computer Science, 9608, through 3. Advanced Theory
Listing 10 of 52 questions
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 .
9608_w19_qp_33
THEORY
2019
Paper 3, Variant 3
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This diagram shows how applications P, Q and a software development environment can be run on a virtual machine system. Application P Application Q Software development environment A operating system 1 Virtual machine software / virtual machine monitor B operating system Hardware A operating system 2 State the operating systems labelled A and B in the diagram. A B Application P is executing and requests data from a file. Describe what happens after A operating system 1 has received the data request from the application. A software development company uses virtual machines to produce software. State one benefit to the company. Explain two limitations of this approach. Limitation 1 Limitation 2
9608_w17_qp_32
THEORY
2017
Paper 3, Variant 2
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The following syntax diagrams, for a particular programming language, show the syntax of: • an assignment statement • a variable • a number • a letter • a digit • an operator Variable Assignment statement Variable Digit := Variable Operator Number Letter Number Number Digit Letter A B C Operator + – / The following assignment statements are invalid. Give a reason in each case. A2 = B3 + 123 Reason B3 := B3 – 203 Reason A2414 := A3 * B Reason Complete the Backus-Naur Form (BNF) for the syntax diagrams shown on the opposite page. has been done for you. ::= ::= ::= ::= A | B | C ::= ::= A company develops software. It provides virtual machines for its software developers. The company has a large number of clients who use a wide range of hardware and software. Explain the term virtual machine. Ensure that your answer includes the terms hardware and software. Give one benefit to the company of using virtual machines. Give one drawback to the company of using virtual machines.
9608_s15_qp_33
THEORY
2015
Paper 3, Variant 3
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Duraid writes a short program in a high-level programming language. An interpreter executes the program. The following is part of Duraid’s program. DECLARE P, Q, R, X, Y : INTEGER CONSTANT M = 10 P = 4 Q = 2 R = 1 X = (P + Q) * (P – Q) Y = (M / Q) * (P + Q - R) Write the Reverse Polish Notation (RPN) for the following expression from Duraid’s program. (P + Q) * (P – Q) The interpreter is executing Duraid’s program. The expressions are in infix form. The interpreter converts the infix to RPN. The RPN expression for Y is: M Q / P Q + R − * The interpreter evaluates this RPN expression using a stack. Show the changing contents of the stack, as the interpreter evaluates the expression for Y. Use the values of the variables and constant given in the program. The first entry has been done for you. Convert the following RPN expression back to its infix form. P Q + M * R P − − Explain how RPN is used by an interpreter to evaluate expressions.
9608_s20_qp_31
THEORY
2020
Paper 3, Variant 1
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Duraid writes a short program in a high-level programming language. An interpreter executes the program. The following is part of Duraid’s program. DECLARE P, Q, R, X, Y : INTEGER CONSTANT M = 10 P = 4 Q = 2 R = 1 X = (P + Q) * (P – Q) Y = (M / Q) * (P + Q - R) Write the Reverse Polish Notation (RPN) for the following expression from Duraid’s program. (P + Q) * (P – Q) The interpreter is executing Duraid’s program. The expressions are in infix form. The interpreter converts the infix to RPN. The RPN expression for Y is: M Q / P Q + R − * The interpreter evaluates this RPN expression using a stack. Show the changing contents of the stack, as the interpreter evaluates the expression for Y. Use the values of the variables and constant given in the program. The first entry has been done for you. Convert the following RPN expression back to its infix form. P Q + M * R P − − Explain how RPN is used by an interpreter to evaluate expressions.
9608_s20_qp_33
THEORY
2020
Paper 3, Variant 3
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A game program is written which can be either interpreted or compiled. The table below shows five statements about the use of interpreters and compilers. Tick (✓) to show whether the statement refers to an interpreter or to a compiler. Statement Interpreter Compiler This translator creates an executable file When this translator encounters a syntax error, game execution halts The translator analyses and checks each line just before executing it This translator will produce faster execution of the game program Use of this translator makes it more difficult for the user to modify the code of the game
9608_w15_qp_11
THEORY
2015
Paper 1, Variant 1
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A game program is written which can be either interpreted or compiled. The table below shows five statements about the use of interpreters and compilers. Tick (✓) to show whether the statement refers to an interpreter or to a compiler. Statement Interpreter Compiler This translator creates an executable file When this translator encounters a syntax error, game execution halts The translator analyses and checks each line just before executing it This translator will produce faster execution of the game program Use of this translator makes it more difficult for the user to modify the code of the game
9608_w15_qp_13
THEORY
2015
Paper 1, Variant 3
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Questions Discovered
52