OCR computing exam questions

OCR computing exam question bn bn bn


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1.(2013) Explain what is meant by an interrupt: Interrupt sent to the p
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rocessor Request for processing time bn bn bn bn

Allows important tasks to be processed
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2.(2013) State two types of interrupts: Power fai
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lure Software interrupt
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Clock interrupt bn

3.(2013) Explain the need for interrupts to have priorities: To decide be
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tween interrupts and current task
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To choose which interrupt if 2 occur
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To ensure most urgent task is performe
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d first. To ensure most efficient use of
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processor
4.(2013) Describe segmentation: A way of partitioning memory segment
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s that are not fixed size
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Segments are logical divisions which complete sections the program.
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5.(2013) State the purpose of virtual memory: To allow programs to r
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un when there is insufficient memory available
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6.(2013) Describe how virtual memory is used: Use of backing store as i
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f it were main memory
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Uses pages bn

Pages are moved from memory to backing store to make space for p
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ges needed bn

7.(2013) Explain one problem that may occur while using virtual memory:
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nDisk threshing bn

More time spent transferring pages than processing
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8.(2013) Describe the code generation phase of translation. Your answe
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r should include reference to optimisation: Code generation occurs aft
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er syntax analysis.
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Produces a machine code program which is equivalent to the source p
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ogram Variables are given addresses
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Relative addresses are calculated bn bn bn




Code optimisation makes code as efficient as po
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ssible Increase processing speed
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Number of instructions is reduced bn bn bn bn


9.(2013) Describe how the contents of the memory address register and
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nthe memory data register change during the fetch-
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execute cycle: Memory address register
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receives address of instruct bn bn bn



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, OCR computing exam question
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ion Holds address of data
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Receives operand part of instruction from the current instruction regis
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, OCR computing exam question
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Memory data register bn bn

Receives an instruction from memory location from memory address r
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gister Receives data from memory location in address part of instruct
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on
10.(2013) Compare co- bn bn

processor and parallel processor systems: Common features
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More than one processor working together to perform a
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single job Job is split into tasks
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Processors are controlled by a single operating s
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ystem Job is completed more quickly
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Differences
Parallel processors can use any processor
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for task Co-
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processors performs specific types of task bn bn bn bn bn b

nonly
Parallel processors need a more complex operating syst
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em Parallel processors are synchronised
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11.(2013) Explain the term class: A template for a set of objects that
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have state and behaviour
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They have methods and attributes represented by the rectangle on th
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bndiagram
12.(2013) Explain plain the term inheritance: A derived class inherits
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all the attributes and operations from its superclass shown by the
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arrow on the diagram bn bn bn

13.(2013) Explain the term capsulation: Data hiding
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Data can only be accessed using operations defined for
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bnthe class Maintains data integrity
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14. (2013) Explain the need for registers: Fast access to data for spec
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ific purposes when frequent access is needed
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Registers are used as a temporary storage bn bn bn bn bn bn

15.(2013) Explain the purpose of the accumulator when a program is b
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eing processed: Temporary storage in arithmetic logic unit
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Holds data being processed during calc
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ulations Deals with input and output in
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the processor bn


16.(2013) Explain why a composite key is used: It creates one to many
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relation- ships as a link table bn bn bn bn bn



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