Pointers and Memory Management

Question 1

What is a memory address?

Answer 1

A unique identifier for a location in memory where data is stored.

Question 2

How is memory allocated when declaring a variable?

Answer 2

The system reserves memory space and updates the lookup table with its address.

Question 3

What happens when you assign a value to a variable?

Answer 3

The system finds the variable in the lookup table, goes to the memory address, and stores the value.

Question 4

What is a pointer?

Answer 4

A variable that stores the memory address of another variable.

Question 5

How do you declare a pointer?

Answer 5

<datatype> *pointer_name;

## Footnote

Example: int *p; declares a pointer to an integer.
</datatype>

Question 6

What does the & operator do?

Answer 6

It returns the memory address of a variable.

Question 7

What does the * operator do when used with a pointer?

Answer 7

It dereferences the pointer to access the value stored at the memory address.

Question 8

How do you assign a pointer to a variable’s address?

Answer 8

p = &variable;

Question 9

What happens when you change the value at a pointer’s address?

Answer 9

The value stored in the original variable changes.

Question 10

How do you print a pointer’s address in C?

Answer 10

Using %p in printf: printf(“Address: %p\n”, p);

Question 11

What happens when you increment a pointer?

Answer 11

The pointer moves to the next memory location based on its data type size.

Question 12

If x is a pointer to an int, what does x++ do?

Answer 12

It moves x to the next integer’s address (typically increasing by 4 bytes).

Question 13

How are arrays and pointers related?

Answer 13

The array name is a pointer to the first element.

Question 14

What is equivalent to array[i] using pointers?

Answer 14

*(array + i)

Question 15

What happens when you assign an array to a pointer?

Answer 15

The pointer stores the address of the first element.

Question 16

What is the output of this code?

char str[] = “Hello”;
char *p = str;
printf(“%s\n”, p);

Answer 16

“Hello”

Question 17

What is a void pointer?

Answer 17

A pointer that can hold the address of any data type.

Question 18

Why do you need to cast a void pointer before dereferencing?

Answer 18

Because its data type is unknown, so you must specify it.

Question 19

How do you cast a void pointer to a char *?

Answer 19

(char *)p

Question 20

Why is dynamic memory allocation needed?

Answer 20

To allocate memory at runtime when the size is unknown at compile time.

Question 21

What function is used to allocate dynamic memory?

Answer 21

malloc()

Question 22

What does malloc() return?

Answer 22

A pointer to the allocated memory (or NULL if allocation fails).

Question 23

What happens if you forget to free memory allocated with malloc()?

Answer 23

A memory leak occurs.

Question 24

How do you free dynamically allocated memory?

Answer 24

free(pointer);

Question 25

What happens if you use a pointer after calling free() on it?

Answer 25

Undefined behavior; it becomes a dangling pointer.

Question 26

What is a segmentation fault?

Answer 26

An error caused by accessing invalid memory.

Question 27

What happens if you dereference an uninitialized pointer?

Answer 27

Undefined behavior, possibly a crash.

Question 28

What is a dangling pointer?

Answer 28

A pointer that still references a memory location after it has been freed.

Question 29

What is a wild pointer?

Answer 29

An uninitialized pointer that points to an unknown memory location.

Question 30

Why must you always check if malloc() returns NULL?

Answer 30

To prevent accessing unallocated memory.

Question 31

What should you always do after malloc()?

Answer 31

Check if the allocation was successful: if (p == NULL) { printf("Memory allocation failed"); exit(1); }

Question 32

What is a good practice before freeing memory?

Answer 32

Set the pointer to NULL after calling free().

Question 33

What tool can help detect memory leaks?

Answer 33

valgrind