Question 1
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a |
Rewrite the following code fragment using the
‘?:’ ternary operator |
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if (a == 6)
b = 7;
else
b = 9; |
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b |
In the following code fragment, explain the differences
between
(i) variables x and y;
(ii) variables m and n;
(iii) variables y and n. |
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...
/* The following two variables are declared outside of any function
*/
int x = 3;
static int y = 3;
...
v oid func1(void)
{
int m = 3;
static int n = 3;
...
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c |
A structure is defined as follows: |
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typedef struct tagContent
{
void *p_data;
int index;
int
*s_data;
} Content;
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Produce a structure that will give
a singly-linked list of “Content” structures. |
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d |
(i) Explain the effect of declaring a variable
to be volatile. (ii) Where is this useful? |
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e |
In the following code fragment, what is the expected
output? |
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unsigned char c = 0xA5;
unsigned char d = 0x3C;
d &= (c | 0x70);
printf(“c is 0x%x\n“, c);
printf(“d is 0x%x\n“, d);
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Question 2
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Each of the following purported implementations
of a ‘C’ standard Library function contain exactly
1 logic error. Describe just that logic error and its remedy
Notes: There are no syntax errors
You should not consider issues of good v. bad style
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a |
The definition of the ‘C’ Library
function memcmp is
int memcmp(const char *cs, const char *ct, size_t n)
Compare the first n characters of cs with the first n characters
of ct.
Return < 0 if cs < ct.
Return > 0 if cs > ct.
Return 0 if cs == ct.
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int memcmp(const char *cs,
const char *ct, size_t n)
{
size_t i; for (i = 0; i < n; i++,
cs++, ct++)
{
if (*cs < *ct)
{
return -1;
}
else if (*cs > *ct)
{
return 1;
}
else
{
return 0;
}
}
}
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b |
The definition of the ‘C’ Library
function strcat is
char *strcat(char *s, const char *ct)
Concatenate ct to the end of s. Return s.
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char *strcat(char *s, const
char *ct)
{
int i, start;
start = strlen(s);
for (i = 0; i < strlen(ct); i++)
{
s[start + i] = ct[i];
}
return s;
}
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c |
The definition of the ‘C’ Library
function memset is
void *memset(char *s, char c, size_t n)
Copy c to the first n characters of s. Return s.
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void *memset(char *s, char
c, size_t n)
{
size_t i; for (i = 0; i < n;
i++, s++)
{
*s = c;
}
return s;
}
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Question 3
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The
definition of library function strspn is:
size_t strspn(const char *str, const char *chars)
Return number of leading characters at the beginning of the string
str which are all members of string chars.
e.g. if ‘str’ is “fecxdy” and ‘chars’
is “abcdef” then the function would return 3, since
‘f’, ’e’ and ‘c’ all appear
somewhere in ‘chars’, giving 3 leading characters
of ‘str’, and ‘x’ is the first character
of ‘str’ which is not a member of ‘chars’.
Write an implementation of strspn in ‘C’. The only
function you may call from your implementation is strlen.
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Question 4
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Answer any parts that you can |
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a |
In ‘C’, there is no language-defined
Boolean type , and an int is often used instead, as in the following
code fragment: |
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int flag = FALSE; |
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(i) Why should a float not be used?
(ii) What would typically happen if you tried to compile the above
fragment? And why?
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b |
Name three facilities for inter-process communication
that you would expect to be provided by a multi-tasking operating
system. |
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c |
Explain how a 32 bit integer 0x1234ABCD is likely
to be stored (a) By a big endian processor and (b) By a little
endian processor. |
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d |
Why can the use of macros be a bad idea? |
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e |
What is a floating point number? |
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f |
List some useful facilities for debugging in
a Set Top Box? |
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Questions