Declarations and Initializations Questions and Answers

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

Correct answer: YesThe inner braces open a new block, and a declaration in an inner block may reuse a name from an outer one - the inner k simply shadows the outer for the extent of that block. It is legal, though the shadowing is a common source of confusion and most compilers will warn about it.

Q: Which of the following declaration is illegal?

Correct answer: char[] str = “...”;C writes the brackets after the identifier, not after the type: char str[]. The form with the brackets before the name belongs to Java. The other three are all valid ways of holding a string, though the third truncates if the literal exceeds the declared size.

Q: What are the types of linkages?

Correct answer: External, Internal and NoneThree linkages exist. External linkage makes a name visible across translation units, internal linkage confines it to one file - which is what static at file scope gives - and no linkage belongs to block-scope names, each declaration of which denotes a distinct object.

Q: How would you round off a value from 1.66 to 2.0?

Correct answer: ceil(1.66)ceil returns the smallest integer not less than its argument, so 1.66 becomes 2.0. floor would give 1.0, and neither roundup nor roundto exists in the standard library - the standard rounding function is round.

Q: Global variable are available to all functions. Does there exist a mechanism by way of which it available to some and not to others.

Correct answer: NoA name with external linkage is visible to every function that declares it, and nothing distinguishes one function from another. What can be restricted is the file: declaring the variable static at file scope confines it to that translation unit. The granularity is the file, not the function.

Q: Which of the following format identifier can never be used for the variable var? int main() { char *var = "Advanced Training in C by AllIndiaExams.com"; }

Correct answer: %fvar is a pointer to char, so %s prints the string, and %d or %c could at least be applied to the pointer value or to a dereferenced character. %f expects a double and could never be given anything derived from this variable, which is what makes it the answer.

Q: Which of the following statements should be used to obtain a remainder after dividing 3.14 by 2.1 ?

Correct answer: rem = fmod(3.14, 2.1);The % operator is defined only for integer operands and will not compile with doubles. fmod from math.h is the floating point equivalent and returns 1.04 here. modf is unrelated - it splits a value into its integer and fractional parts.

Q: Is it true that a function may have several declarations, but only one definition?

Correct answer: YesA prototype may appear in every file that calls the function, and usually does by way of a header, but the body is written once. The rule is the same as for objects: declarations may be repeated, and the definition may not.

Q: Which of the following is not a pointer declaration?

Correct answer: char a;An array name decays to a pointer to its first element in nearly every context, so the first two declarations yield something usable as a pointer, and char *str is one outright. A plain char holds a single character and has no pointer nature at all.

Q: Is it true that a global variable may have several declarations, but only one definition?

Correct answer: YesEvery file using a global variable declares it, so a program may contain many declarations of one object. The storage is reserved once, by the single definition, and the linker resolves every declaration to it. More than one definition is an error at link time.

11.

Does this compile without error?

int main()
{
int k;
{
int k;
for (k = 0; k < 10; k++);
}
}

A.Yes
B.No
C.Depends on the compiler
D.Depends on the C standard implemented by compilers

Answer: A

Correct answer: Yes

The inner braces open a new block, and a declaration in an inner block may reuse a name from an outer one - the inner k simply shadows the outer for the extent of that block. It is legal, though the shadowing is a common source of confusion and most compilers will warn about it.

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12.

Which of the following declaration is illegal?

A.char *str = “Best C programming classes by AllIndiaExams”;
B.char str[] = “Best C programming classes by AllIndiaExams”;
C.char str[20] = “Best C programming classes by AllIndiaExams”;
D.char[] str = “Best C programming classes by AllIndiaExams”;

Answer: D

Correct answer: char[] str = “...”;

C writes the brackets after the identifier, not after the type: char str[]. The form with the brackets before the name belongs to Java. The other three are all valid ways of holding a string, though the third truncates if the literal exceeds the declared size.

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13.

What are the types of linkages?

A.Internal and External
B.External, Internal and None
C.External and None
D.Internal

Answer: B

Correct answer: External, Internal and None

Three linkages exist. External linkage makes a name visible across translation units, internal linkage confines it to one file - which is what static at file scope gives - and no linkage belongs to block-scope names, each declaration of which denotes a distinct object.

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14.

How would you round off a value from 1.66 to 2.0?

A.ceil(1.66)
B.floor(1.66)
C.roundup(1.66)
D.roundto(1.66)

Answer: A

Correct answer: ceil(1.66)

ceil returns the smallest integer not less than its argument, so 1.66 becomes 2.0. floor would give 1.0, and neither roundup nor roundto exists in the standard library - the standard rounding function is round.

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15.

Global variable are available to all functions. Does there exist a mechanism by way of which it available to some and not to others.

A.Yes
B.No

Answer: B

Correct answer: No

A name with external linkage is visible to every function that declares it, and nothing distinguishes one function from another. What can be restricted is the file: declaring the variable static at file scope confines it to that translation unit. The granularity is the file, not the function.

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16.

Which of the following format identifier can never be used for the variable var?

int main()
{
char *var = "Advanced Training in C by AllIndiaExams.com";
}

A.%f
B.%d
C.%c
D.%s

Answer: A

Correct answer: %f

var is a pointer to char, so %s prints the string, and %d or %c could at least be applied to the pointer value or to a dereferenced character. %f expects a double and could never be given anything derived from this variable, which is what makes it the answer.

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17.

Which of the following statements should be used to obtain a remainder after dividing 3.14 by 2.1 ?

A.rem = 3.14 % 2.1;
B.rem = modf(3.14, 2.1);
C.rem = fmod(3.14, 2.1);
D.Remainder cannot be obtain in floating point division.

Answer: C

Correct answer: rem = fmod(3.14, 2.1);

The % operator is defined only for integer operands and will not compile with doubles. fmod from math.h is the floating point equivalent and returns 1.04 here. modf is unrelated - it splits a value into its integer and fractional parts.

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18.

Is it true that a function may have several declarations, but only one definition?

A.Yes
B.No

Answer: A

Correct answer: Yes

A prototype may appear in every file that calls the function, and usually does by way of a header, but the body is written once. The rule is the same as for objects: declarations may be repeated, and the definition may not.

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19.

Which of the following is not a pointer declaration?

A.char a[10];
B.char a[] = {’1', ’2', ’3', ’4'};
C.char *str;
D.char a;

Answer: D

Correct answer: char a;

An array name decays to a pointer to its first element in nearly every context, so the first two declarations yield something usable as a pointer, and char *str is one outright. A plain char holds a single character and has no pointer nature at all.

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20.

Is it true that a global variable may have several declarations, but only one definition?

A.Yes
B.No

Answer: A

Correct answer: Yes

Every file using a global variable declares it, so a program may contain many declarations of one object. The storage is reserved once, by the single definition, and the linker resolves every declaration to it. More than one definition is an error at link time.

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