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Functions

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All Basics & Syntax 100 Data Types & Variables 100 Control Flow 100 Functions 100 Arrays & Strings 100 Pointers 100 Structures & Unions 100 File Handling 100 Dynamic Memory 100 Preprocessor 100

Q.41 Easy Functions

Which of the following is a valid function declaration in C?

A int func(void);

B func int();

C void int func();

D int func() void;

Correct Answer: A. int func(void);

EXPLANATION

The correct syntax is return_type function_name(parameters). Option A follows proper C syntax with int as return type, func as name, and void indicating no parameters.

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Q.42 Easy Functions

What is the primary purpose of function prototypes in C?

A To declare the function signature before its definition

B To allocate memory for function variables

C To optimize function execution speed

D To prevent function from being called

Correct Answer: A. To declare the function signature before its definition

EXPLANATION

Function prototypes inform the compiler about function name, return type, and parameters before the actual definition, enabling proper type checking during compilation.

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Q.43 Hard Functions

Which approach is more efficient for passing large structures to functions?

A Pass by value (entire structure copied)

B Pass by pointer (only address passed)

C Pass by reference (not available in C)

D Use extern to share globally

Correct Answer: B. Pass by pointer (only address passed)

EXPLANATION

Passing large structures by pointer is more efficient as only address (typically 4-8 bytes) is copied, not entire structure.

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Q.44 Hard Functions

In C99 standard, what is true about function declarations at block scope?

A Functions cannot be declared inside blocks

B Function declarations inside blocks have local scope

C Such declarations are only valid with extern keyword

D Block scope declarations create implicit static storage

Correct Answer: B. Function declarations inside blocks have local scope

EXPLANATION

C99 allows function declarations within blocks; they have scope limited to that block. This is different from function definitions which remain at file scope.

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Q.45 Medium Functions

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); }

A 10 5

B 5 10

C 0 0

D Garbage values

Correct Answer: B. 5 10

EXPLANATION

This is call-by-value. The function swaps copies of x and y, not the originals. Original values remain unchanged.

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Q.46 Hard Functions

Analyze: int (*funcPtr)(int, int); What does this declaration represent?

A A function that takes two integers and returns pointer

B A pointer to function taking two integers returning int

C Array of function pointers

D A structure containing function pointer

Correct Answer: B. A pointer to function taking two integers returning int

EXPLANATION

The syntax (*funcPtr) indicates funcPtr is a pointer. It points to functions taking two ints and returning int.

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Q.47 Hard Functions

What is the correct way to return multiple values from a function in C?

A return a, b, c; // Multiple return values

B Use pointers as output parameters

C Use struct to bundle values and return struct

D Both B and C are correct approaches

Correct Answer: D. Both B and C are correct approaches

EXPLANATION

C doesn't support multiple return values. Both pointers (call-by-reference) and structs are valid techniques.

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Q.48 Hard Functions

Consider mutual recursion: void funcA(int n); void funcB(int n); funcA calls funcB and vice versa. What is required?

A Forward declaration of at least one function

B Both functions must be defined before any call

C Mutual recursion is not allowed in C

D Extra extern keyword for both functions

Correct Answer: A. Forward declaration of at least one function

EXPLANATION

For mutual recursion, you need forward declaration (prototype) of at least one function before it's called by another.

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Q.49 Hard Functions

What will happen if a recursive function has no base case?

A Compiler error

B Stack overflow at runtime

C Function returns NULL

D Infinite loop continues forever

Correct Answer: B. Stack overflow at runtime

EXPLANATION

Without base case, recursion never stops, causing stack to overflow as return addresses keep accumulating.

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Q.50 Medium Functions

Which of the following correctly demonstrates inline function usage for optimization?

A inline void process() { } // Always inlined

B inline int square(int x) { return x*x; } // Compiler may inline

C void inline() { } // Syntax error

D Inline functions are not part of C standard

Correct Answer: B. inline int square(int x) { return x*x; } // Compiler may inline

EXPLANATION

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.

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C Programming
Functions