Which function is used to reverse a string in C library?

The correct answer is C: String reversal is not in standard C library. There is no standard library function for string reversal. strrev() is non-standard (available in some compilers). Manual reversal or custom functions are needed.

What is the scope of a static variable declared inside a function?

The correct answer is A: Local to the function, but retains value between calls. Static variables inside a function have local scope but static storage duration, meaning they retain their value between function calls and are initialized only once.

Which of the following correctly uses memcpy()?

The correct answer is D: memcpy(dest, src, count);. memcpy(dest, src, count) copies 'count' bytes from src to dest. strlen() and sizeof() may not give correct results for all data types.

How many times will a do-while loop execute if the condition is initially false?

The correct answer is B: At least once. A do-while loop executes the body at least once before checking the condition. Even if the condition is false, the body executes one time.

Which scenario is most likely to cause a segmentation fault in dynamic memory?

The correct answer is B: Accessing memory beyond allocated size. Buffer overflow by accessing beyond allocated boundaries causes segmentation fault as it accesses invalid memory pages.

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C Programming
Structures & Unions

C language from basics to advanced placement prep

46 Q 10 Topics Take Mock Test

Difficulty: All Easy Medium Hard 41–46 of 46

Topics in C Programming

All Basics & Syntax 86 Data Types & Variables 97 Control Flow 100 Functions 99 Arrays & Strings 100 Pointers 99 Structures & Unions 100 File Handling 100 Dynamic Memory 98 Preprocessor 99

Q.41 Medium Structures & Unions

What is the purpose of padding in structures?

A To waste memory intentionally

B To align data for faster CPU access

C To prevent hacking

D To increase security

Correct Answer: B. To align data for faster CPU access

EXPLANATION

Padding ensures that structure members are aligned in memory according to their natural boundaries, improving CPU access speed.

Test

Q.42 Medium Structures & Unions

How do you access a member of a structure using a pointer?

A ptr.member

B ptr->member

C *ptr.member

D ptr*member

Correct Answer: B. ptr->member

EXPLANATION

The arrow operator (->) is used to access structure members through a pointer. Dot (.) is for direct variables.

Test

Q.43 Medium Structures & Unions

What will be printed?
struct s { int a; char b; int c; }; printf("%lu", sizeof(struct s));

A 9 bytes

B 12 bytes

C 13 bytes

D 8 bytes

Correct Answer: B. 12 bytes

EXPLANATION

Due to memory alignment/padding: int a(4) + char b(1) + 3 padding bytes + int c(4) = 12 bytes.

Test

Q.44 Medium Structures & Unions

What is the difference between struct and typedef struct?

A No difference, both are identical

B typedef struct allows direct variable declaration without 'struct' keyword

C struct is faster than typedef struct

D typedef struct is used only in C++

Correct Answer: B. typedef struct allows direct variable declaration without 'struct' keyword

EXPLANATION

typedef struct creates an alias, so you can declare variables directly using the alias name without repeating 'struct'.

Test

Q.45 Medium Structures & Unions

Which of the following correctly declares a pointer to a structure?

A struct emp *ptr;

B *struct emp ptr;

C struct *emp ptr;

D emp struct *ptr;

Correct Answer: A. struct emp *ptr;

EXPLANATION

Correct syntax is 'struct typename *pointerName;'. Option A follows proper declaration syntax.

Test

Q.46 Medium Structures & Unions

What happens when you initialize a structure variable without assigning values?

A Members are automatically set to 0

B Members contain garbage values

C Compilation error occurs

D Members are set to NULL

Correct Answer: B. Members contain garbage values

EXPLANATION

Uninitialized local structure variables contain garbage values. Global structures are automatically initialized to zero.

Test

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C Programming Structures & Unions

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Structures & Unions