What is the purpose of the clearerr() function in file handling?

The correct answer is A: To clear the EOF indicator and error flags for a stream. clearerr() clears both the EOF indicator and the error flag associated with a stream.

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

The correct answer is B: Pass by pointer (only address passed). Passing large structures by pointer is more efficient as only address (typically 4-8 bytes) is copied, not entire structure.

In the context of function pointers, what does the restrict keyword do?

The correct answer is B: Tells the compiler that the pointer is the only way to access the data. The restrict keyword informs the compiler that the pointer is the sole means of accessing the data it points to, allowing for optimization. It's a hint for compiler optimization.

How does free() handle a NULL pointer?

The correct answer is B: Does nothing (safe operation). free(NULL) is safe in C and does nothing. This is by design to prevent errors when freeing pointers.

Which operator is used to get the address of a variable?

The correct answer is B: & (ampersand). The & (address-of) operator returns the memory address of a variable.

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C Programming
Dynamic Memory

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53 Q 10 Topics Take Mock Test

Difficulty: All Easy Medium Hard 41–50 of 53

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 Dynamic Memory

Consider reallocating memory:
int *p = malloc(10);
p = realloc(p, 20);

A The original 10 bytes are lost

B realloc() preserves existing data and allocates additional memory

C realloc() always returns a new address

D Memory at address p is deallocated first

Correct Answer: B. realloc() preserves existing data and allocates additional memory

EXPLANATION

realloc() extends the existing allocation, preserving original data, and may return the same or different address.

Test

Q.42 Medium Dynamic Memory

What is the output of this code?
int *p = calloc(3, sizeof(int));
printf("%d %d %d", p[0], p[1], p[2]);

A Random values

B 0 0 0

C Garbage, Garbage, Garbage

D Compilation error

Correct Answer: B. 0 0 0

EXPLANATION

calloc() initializes all allocated bytes to 0, so all integers are 0.

Test

Q.43 Medium Dynamic Memory

Analyze the memory leak in this code:
void func() {
int *p = malloc(100);
if(condition) return;
free(p);
}

A No memory leak; free() is called before return

B Memory leak occurs when condition is true (p is not freed)

C Memory leak occurs in all cases

D No leak, malloc() automatically frees memory

Correct Answer: B. Memory leak occurs when condition is true (p is not freed)

EXPLANATION

When condition is true, the function returns without calling free(), causing a memory leak.

Test

Q.44 Medium Dynamic Memory

What is the purpose of typecasting in malloc()?
int *p = (int*)malloc(sizeof(int));

A It is mandatory in C

B It improves memory allocation speed

C It improves code readability and is good practice (optional in C, mandatory in C++)

D It prevents memory leaks

Correct Answer: C. It improves code readability and is good practice (optional in C, mandatory in C++)

EXPLANATION

Typecasting malloc() is optional in C but improves readability. It's mandatory in C++.

Test

Q.45 Medium Dynamic Memory

Which of the following correctly allocates memory for an array of 5 strings (each max 20 characters)?

A char *str = malloc(5 * 20);

B char **str = malloc(5 * sizeof(char*)); for(int i=0; i

C char str[5][20];

D Both B and C are valid approaches

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

EXPLANATION

Option B uses dynamic allocation (2D array), Option C uses static allocation. Both are valid but for different scenarios.

Test

Q.46 Medium Dynamic Memory

What is the output?
int *p = malloc(sizeof(int) * 3);
p[0] = 1; p[1] = 2; p[2] = 3;
printf("%d", *(p+2));

A 1

B 2

C 3

D Compilation error

Correct Answer: C. 3

EXPLANATION

*(p+2) is equivalent to p[2], which contains 3. Pointer arithmetic works with dynamic arrays.

Test

Q.47 Medium Dynamic Memory

Analyze this code:
char *str = malloc(5);
strcpy(str, "Hello");
How many bytes should malloc allocate for safety?

A 5

B 6

C 4

D 7

Correct Answer: B. 6

EXPLANATION

String "Hello" has 5 characters plus 1 null terminator (\0), requiring 6 bytes total.

Test

Q.48 Medium Dynamic Memory

What is double free error?

A Allocating memory twice

B Calling free() on already freed memory

C Using two pointers to same memory

D Allocating memory twice and freeing once

Correct Answer: B. Calling free() on already freed memory

EXPLANATION

Double free error occurs when free() is called on the same memory block twice, causing undefined behavior and program crash.

Test

Q.49 Medium Dynamic Memory

Which of the following is correct for dynamic array allocation?

A int arr[n]; where n is variable

B int *arr = malloc(n * sizeof(int));

C int arr = malloc(n);

D int *arr[n];

Correct Answer: B. int *arr = malloc(n * sizeof(int));

EXPLANATION

Dynamic array allocation requires pointer and malloc() with proper size calculation. VLAs are not standard C.

Test

Q.50 Medium Dynamic Memory

What is the purpose of realloc() function?

A To allocate new memory

B To resize previously allocated memory block

C To free memory

D To initialize memory

Correct Answer: B. To resize previously allocated memory block

EXPLANATION

realloc() resizes a previously allocated memory block. It can increase or decrease the size and preserves existing data.

Test

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