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(a) Describe the relationship
between a pointer and an array. |
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A variable
declared as an array can be manipulated as a pointer |
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to the
first element of the array. |
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A pointer
is not necessarily an array. |
[1] |
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(b) Describe the difference
between call by reference and call by value parameter passing. |
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If a
formal parameter of a function or procedure is passed via a call-by-reference parameter
passing scheme, then any changes to that variable during the lifetime of the procedure
invocation will carry through after the procedure has returned. |
[1] |
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In
contrast, changes to variables which are passed using the call-by-value scheme are only
retained during the lifetime of the procedure/function invocation. |
[1] |
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(c) Write a procedure called
replace that takes two integer arguments, called sum and diff. It should change the values
of these two variables so that the value of sum on exit is equal to the sum of the two
values on entry, and the value of diff on exit is equal to the difference between the two
values on entry. |
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Two
definitions of the replace procedure are shown below: |
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and the
following marking scheme should be used: |
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two marks for
the procedure declaration. If the declaration just contains int sum, int diff, then award
no marks, but mark the points below as though any references to sum where actually *sum. |
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one mark for
declaring a temporary variable and assigning *sum or *diff to it. |
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If the
temporary variable contains the value for *sum |
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then award one mark
incrementing *sum by *diff. |
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one mark for subtracting
*diff from temp, and assigning the result to *diff. |
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If the
temporary variable contains the value for *diff |
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one mark for subtracting
*sum from *diff, and assigning the result to *diff. |
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then award one mark
incrementing *sum by temp. |
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no marks
should be deducted for trivial syntactic errors. |
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[5
marks] |
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(d) Trace the following code
segment and produce the output: |
[10] |
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Award one mark
for each of numbers in the output below. Do not deduct marks if the answers do not include
the accompanying text such as first =.
| first = 66 |
second = 66 |
| third = 59 |
fourth = 52 |
| fifth = 64 |
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