Pointers in C: Memory Management, Function Pointers & Dynamic Allocation with Examples

Pointers in C
Pointers in C are variables that store memory addresses. Instead of holding a data
value directly, a pointer holds the address of a variable. Pointers are a powerful
feature in C, allowing for dynamic memory allocation, efficient array
manipulation, and implementing data structures like linked lists and trees.

1. Declaring Pointers
To declare a pointer, you use the * operator, which specifies that the variable will
store a memory address.

The basic syntax for declaring a pointer is:

data_type *pointer_name;

Example:

#include <stdio.h>

int main() {
int num = 10;
int *ptr; // Pointer to an integer

ptr = &num; // Storing the address of 'num' in 'ptr'

printf("Value of num: %d\n", num); // Output: 10
printf("Address of num: %p\n", (void*)&num); // Output: Memory address of
num
printf("Value stored in ptr (address of num): %p\n", (void*)ptr); // Output:
Address of num
printf("Dereferencing ptr (value at ptr): %d\n", *ptr); // Output: 10

return 0;
}

, Here, ptr is a pointer to an integer, and it holds the address of num. The &
operator gives the address of a variable, and the * operator is used to
dereference a pointer (access the value stored at that address).



2. Pointer Dereferencing
Dereferencing a pointer means accessing the value at the memory address the
pointer is pointing to.

The syntax to dereference a pointer is:

*pointer_name

Example:

#include <stdio.h>

int main() {
int num = 25;
int *ptr = &num; // Pointer holds the address of num

printf("Value of num: %d\n", num); // Output: 25
printf("Value at ptr (dereferencing): %d\n", *ptr); // Output: 25

return 0;
}

In this example, dereferencing ptr gives the value of num.



3. Pointer to Pointer
A pointer can also point to another pointer, which is known as a pointer to a
pointer.