What is the output of this C code?
void main()
{
int k = 4;
float k = 4;
printf("%d", k)
}
Answer: A
Correct answer: Compile time error
The same identifier is declared twice in one scope with different types, which the language forbids: k cannot be both an int and a float. The error is diagnosed at compile time, so no output is produced at all.
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Does this compile without error?
int main()
{
int k;
{
int k;
for (k = 0; k < 10; k++);
}
}
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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Which of the following declaration is illegal?
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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What are the types of linkages?
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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How would you round off a value from 1.66 to 2.0?
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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Global variable are available to all functions. Does there exist a mechanism by way of which it available to some and not to others.
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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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";
}
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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Which of the following statements should be used to obtain a remainder after dividing 3.14 by 2.1 ?
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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Is it true that a function may have several declarations, but only one definition?
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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Which of the following is not a pointer declaration?
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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