pointers

Every variable in C has an address.

A pointer is just a variable that stores the address of another variable.

Example:

int a = 10;    // normal variable
int *b = &a;   // pointer storing address of a

• &a → gives the address of a.
• &b → gives the address of the pointer b itself.

To get the value stored at the address, we dereference the pointer:

*b  // this gives 10, the value of a

You can also change the value of a through the pointer:

*b = 20;  // now a is 20

So basically, pointers = addresses, and * lets you reach the value at that address.

Pointers are super important for arrays too.

Example:

int nums[] = {1, 2, 3, 4, 5};

If we pass nums to a function, it actually sends the address of the first element:

void display(int* nums, int nums_size) {
    for (int i = 0; i < nums_size; i++) {
        printf("%d", nums[i]);
    }
}

These two calls are equivalent:

display(nums, nums_size);
display(&nums[0], nums_size);

Output:

12345
12345

So yeah, arrays and pointers are basically best friends in C. Passing an array to a function is just passing a pointer to its first element