C questions in placement tests and university exams are rarely about syntax alone. Most of what you will find here is output prediction, pointer arithmetic, arrays and strings, structures and unions, storage classes, recursion, and file handling. The explanations walk through memory behaviour step by step, which is usually where the confusion sits rather than in the code itself.
How does the volatile keyword affect function behavior in C?
Answer: B
The volatile keyword tells the compiler not to optimize away variable accesses, ensuring the variable is read from memory each time.
Q.322Medium
Which of the following is a valid function pointer initialization?
Answer: D
Both forms are valid. Functions decay to function pointers, so both &printf and printf assign the function address correctly.
Q.323Easy
Which storage class specifier allows a function to be called only within the file where it is defined?
Answer: A
The static keyword restricts function scope to the file in which it is declared, preventing external linkage.
Q.324Easy
What is the return type of a function that performs an action but doesn't return any value?
Answer: B
The void keyword is used as return type for functions that do not return any value.
Q.325Easy
In C, what happens when a function is called before its declaration?
Answer: B
C requires function declaration before use (forward declaration or definition). Calling without prior declaration causes compilation error in modern C standards.
Q.326Easy
Which of the following is an example of call by value in C?
Answer: B
Call by value passes a copy of the variable. Changes inside the function don't affect the original variable. Option B demonstrates this principle.
Q.327Easy
What is the main difference between function declaration and function definition?
Answer: A
Declaration (prototype) informs compiler about function signature; definition provides the actual implementation body.
Q.328Medium
Consider the code: int calculate(int a, int b = 5) { return a + b; }. What is the issue?
Answer: B
Default parameters are a C++ feature, not available in standard C. C requires explicit arguments for all parameters.
Q.329Medium
What will be the output of this recursive function? int fact(int n) { if(n <= 1) return 1; return n * fact(n-1); } fact(5)
Answer: C
This calculates factorial. fact(5) = 5*4*3*2*1 = 120. Base case n<=1 stops recursion.
Q.330Medium
Which statement about function parameters passed as arrays is correct?
Answer: B
Arrays in C decay to pointers to their first element, effectively making them pass-by-reference. Changes inside function affect original array.
Q.331Medium
What is the purpose of the 'extern' keyword when used with a function?
Answer: A
extern allows you to declare a function defined elsewhere, enabling its use across multiple translation units.
Q.332Medium
Consider: void modify(int *ptr) { *ptr = 20; } int main() { int x = 10; modify(&x); printf("%d", x); }. Output?
Answer: B
This is call by reference using pointers. The function receives address of x, dereferences and modifies it to 20.
Q.333Medium
What does variadic function mean in C?
Answer: A
Variadic functions accept variable number of arguments using ellipsis (...) and accessed with va_list, va_arg macros.
Q.334Medium
Which of the following correctly demonstrates inline function usage for optimization?
Answer: B
inline is a hint to compiler to expand function at call site. It's supported in C99+ and compiler decides whether to inline or not.
Q.335Hard
What will happen if a recursive function has no base case?
Answer: B
Without base case, recursion never stops, causing stack to overflow as return addresses keep accumulating.
Q.336Hard
Consider mutual recursion: void funcA(int n); void funcB(int n); funcA calls funcB and vice versa. What is required?
Answer: A
For mutual recursion, you need forward declaration (prototype) of at least one function before it's called by another.
Q.337Hard
What is the correct way to return multiple values from a function in C?
Answer: D
C doesn't support multiple return values. Both pointers (call-by-reference) and structs are valid techniques.
Q.338Hard
Analyze: int (*funcPtr)(int, int); What does this declaration represent?
Answer: B
The syntax (*funcPtr) indicates funcPtr is a pointer. It points to functions taking two ints and returning int.
Q.339Medium
What is the output of this code? void swap(int a, int b) { int temp = a; a = b; b = temp; } int main() { int x = 5, y = 10; swap(x, y); printf("%d %d", x, y); }
Answer: B
This is call-by-value. The function swaps copies of x and y, not the originals. Original values remain unchanged.
Q.340Hard
In C99 standard, what is true about function declarations at block scope?
Answer: B
C99 allows function declarations within blocks; they have scope limited to that block. This is different from function definitions which remain at file scope.
