Can a function return an enumeration constant in C?
Answer: A
Correct answer: true
An enumeration constant is an integer constant, so a function can return one exactly as it returns any int - and a function may equally be declared to return the enumeration type itself.
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What is the output of this code having void return-type function?
void foo()
{
return 1;
}
void main()
{
int x = 0;
x = foo();
printf("%d", x);
}
Answer: C
Correct answer: Compile time error
A void function must not return a value, so return 1; is an error - and assigning the result of a void function to an int is a second one. Either alone would stop the program compiling.
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The output of the code below is
int *m();
void main()
{
int k = m();
printf("%d", k);
}
int *m()
{
int a[2] = {5, 8};
return a;
}
Answer: D
Correct answer: Varies
Two faults compound each other. The function returns a pointer to a local array that no longer exists, and the caller assigns that pointer to an int. What is printed is an address reinterpreted as an integer - different on every run and every machine.
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Maximum number of arguments that a function can take is 12
Answer: B
Correct answer: No
The standard sets no limit of twelve. It requires an implementation to support at least 127 parameters, and most allow far more - so the practical limit is the compiler’s, not the language’s. (A function needing many parameters is usually better given a structure.)
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What is the output of this C code?
static int x;
void main()
{
int x;
printf("x is %d", x);
}
Answer: A
Correct answer: Junk value
The local int x; shadows the file-scope static, and being an automatic variable with no initialiser it holds whatever was on the stack - a junk value. Only variables with static storage duration are zeroed for you.
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Functions cannot return more than one value at a time
Answer: A
Correct answer: True
A C function returns at most one value. Where more is needed the usual devices are to pass pointers for the extra results, or to return a structure containing them all.
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What linkage does automatic variables have?
Answer: C
Correct answer: No linkage
An automatic variable has no linkage: its name refers to a fresh object on each entry to the block and cannot be referred to from anywhere else - not from another file, not even from another function. Only file-scope names have linkage, internal or external.
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What is the output of this C code?
void main()
{
int x = 3;
{
x = 4;
printf("%d", x);
}
}
Answer: A
Correct answer: 4
The inner block contains an assignment, not a declaration, so it changes the x already in scope. The value printed is 4.
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What is the return type of the function sqrt()?
Answer: C
Correct answer: double
sqrt is declared in <math.h> as double sqrt(double) - it takes and returns a double. C99 added sqrtf and sqrtl for float and long double, but the return type of sqrt itself does not vary with the argument.
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What is the output of this C code?
void foo();
int main()
{
void foo(int);
foo(1);
return 0;
}
void foo(int i)
{
printf("2 ");
}
Answer: A
Correct answer: 2
The declaration inside main - void foo(int) - is the one in scope at the call, so foo(1) matches it, and it agrees with the definition. The outer void foo() declares a function with an unspecified parameter list rather than none, so it does not conflict. The program prints 2.
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