What is the output of this C code?
void foo();
int main()
{
void foo();
foo();
return 0;
}
void foo()
{
printf("2 ");
}
Answer: B
Correct answer: 2
The function is declared at file scope and again inside main. Repeating a declaration is harmless as long as the two agree, which they do, so the program compiles and prints 2.
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Which of the following storage classes supports the char data type?
Answer: D
Correct answer: All of the mentioned
char works with every storage class: auto char, static char and register char are all valid. Storage class and type are independent choices - the first says where and how long the object lives, the second what it holds.
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What is the output of this C code?
int main()
{
void foo(), f();
f();
}
void foo()
{
printf("2 ");
}
void f()
{
printf("1 ");
foo();
}
Answer: B
Correct answer: 1 2
Declaring void foo(), f(); inside main is legal - it declares them, without defining them, and the declaration is simply local in scope. f() is then called; it prints 1 and calls foo, which prints 2. Output: 1 2.
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What is the format identifier for “static a = 20.5;”?
Answer: B
Correct answer: %d
With no type given, static a = 20.5; falls back on the old implicit int, so the value is truncated to 20 and the correct specifier is %d. The declaration is legal only under the pre-C99 rules; a modern compiler will warn or reject it.
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Functions have the static qualifier by default.
Answer: B
Correct answer: false
Functions have external linkage by default, not static - which is why a function defined in one file can be called from another. Writing static before a function is what confines it to its own file.
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The value computed in a function is given back to the caller using the ________ keyword.
Answer: A
Correct answer: return
return both ends the function and passes the value back. static, new and volatile have nothing to do with it - and new is not even a C keyword.
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What is the problem in the following declarations?
int func(int);
double func(int);
int func(float);
Answer: D
Correct answer: All of the mentioned
C has no function overloading: one name may denote only one function in a translation unit. So none of the three variations is allowed - not a different signature, not a different return type, not a different number of parameters. (C++ permits overloading on the parameters, though still not on the return type alone.)
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Array sizes are optional during array declaration by using ______ keyword.
Answer: C
Correct answer: extern
An extern declaration says the array is defined elsewhere, so its size may be omitted: extern int a[];. The definition in the other file supplies the size. Note the consequence - sizeof cannot be applied to it in this file, since the compiler does not know how big it is.
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Which of the following cannot be static in C?
Answer: D
Correct answer: None of the mentioned
Variables and functions can both be static, which gives them internal linkage or, for a local variable, a lifetime as long as the program’s. A structure variable can be static too. What cannot be static is a structure type - but a type has no storage class in the first place.
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In C all functions except main() can be called recursively.
Answer: B
Correct answer: False
main can be called recursively in C - it is an ordinary function in that respect, and the standard permits it. (C++ forbids it.) So the statement that every function except main may recurse is false.
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