Questions and answers for exam Preparation

MCQs

Total Questions : 13 | Page 1 of 2 pages

Question 1. What is the output of this C code?
void foo(const int *);
int main()
{
const int i = 10;
printf("%d ", i);
foo(&i);
printf("%d", i);
}
void foo(const int *i)
{
*i = 20;
}

Compile time error
10 20
Undefined value
10

Discuss Question

Answer: Option A. -> Compile time error

Cannot change a const type value.
Output:
$ cc pgm1.c
pgm1.c: In function 'foo':
pgm1.c:13: error: assignment of read-only location '*i'

Question 2. Comment on the output of this C code?
int main()
{
const int i = 10;
int *ptr = &i;
*ptr = 20;
printf("%d\n", i);
return 0;
}

Compile time error
Compile time warning and printf displays 20
Undefined behaviour
10

Discuss Question

Answer: Option B. -> Compile time warning and printf displays 20

Changing const variable through non-constant pointers invokes compiler warning
Output:
$ cc pgm2.c
pgm2.c: In function 'main':
pgm2.c:5: warning: initialization discards qualifiers from pointer target type
$ a.out
20

Question 3. Does this compile without error?
int main()
{
for (int k = 0; k < 10; k++);
return 0;
}

Yes
No
Depends on the C standard implemented by compilers
None of the mentioned

Discuss Question

Answer: Option C. -> Depends on the C standard implemented by compilers

Compilers implementing C90 does not allow this but compilers implementing C99 allow it.
Output:
$ cc pgm4.c
pgm4.c: In function 'main':
pgm4.c:4: error: 'for' loop initial declarations are only allowed in C99 mode
pgm4.c:4: note: use option -std=c99 or -std=gnu99 to compile your code

Question 4. What is the output of this C code?
int main()
{
j = 10;
printf("%d\n", j++);
return 0;
}

10
11
Compile time error
0

Discuss Question

Answer: Option C. -> Compile time error

Variable j is not defined.
Output:
$ cc pgm3.c
pgm3.c: In function 'main':
pgm3.c:4: error: 'j' undeclared (first use in this function)
pgm3.c:4: error: (Each undeclared identifier is reported only once
pgm3.c:4: error: for each function it appears in.)

Question 5. Does this compile without error?
int main()
{
int k;
{
int k;
for (k = 0; k < 10; k++);
}
}

Yes
No
Depends on the compiler
Depends on the C standard implemented by compilers

Discuss Question

Answer: Option A. -> Yes

There can be blocks inside block and within blocks variables have only block scope.
Output:
$ cc pgm5.c

Question 6. Which of the following declaration is not supported by C?

String str;
char *str;
float str = 3e2;
Both (a) and (c)

Discuss Question

Answer: Option A. -> String str;

It is legal in Java, not in C.

Question 7. Which of the following is not a pointer declaration?

char a[10];
char a[] = {'1', '2', '3', '4'};
char *str;
char a;

Discuss Question

Answer: Option D. -> char a;

Array declarations are pointer declarations.

Question 8. Which of the following declaration is illegal?

char *str = Best C programming classes by AllIndiaExams";
char str[] = Best C programming classes by AllIndiaExams";
char str[20] = Best C programming classes by AllIndiaExams";
char[] str = Best C programming classes by AllIndiaExams";

Discuss Question

Answer: Option A. -> char *str = Best C programming classes by AllIndiaExams";

char[] str is a declaration in Java, not in C.

Question 9. Which keyword is used to prevent any changes in the variable within a C program?

immutable
mutable
const
volatile

Discuss Question

Answer: Option C. -> const

const is a keyword constant in C program.

Question 10. What is the output of this C code?
void main()
{
int k = 4;
float k = 4;
printf("%d", k)
}

Compile time error
4
4.0000000
4.4

Discuss Question

Answer: Option A. -> Compile time error

Since the variable k is defined both as integer and as float, it results in an error.
Output:
$ cc pgm8.c
pgm8.c: In function 'main':
pgm8.c:5: error: conflicting types for 'k'
pgm8.c:4: note: previous definition of 'k' was here
pgm8.c:6: warning: format '%d' expects type 'int', but argument 2 has type 'double'
pgm8.c:7: error: expected ';' before '}' token