Pointer Arithmetic: Traversing Memory without an Index

Why use an Index when you can touch the Memory? 👉

Day 2/30: Pointer Arithmetic.

Most tutorials teach you to loop through arrays using i (the index). But in Systems Programming, we often manipulate the address directly.

The Magic: When you write ptr++ in C, the compiler is smart. It doesn't just add "1" to the address. It adds sizeof(int) (usually 4 bytes).

If ptr was a char, it would add 1 byte. If ptr was a struct, it would jump the size of the whole struct.

This snippet allows us to iterate through data purely by comparing memory addresses, which is more direct and cleaner in low-level drivers.

The Code

Here is the C code for Day 2:

// Day 2: Traversing Memory without an Index

void iterate_with_pointers(const int *ptr, int size) {
    // We don't need 'i' or 'array[i]'
    // We just look at the end address
    int *end = ptr + size;

    while (ptr < end) {
        // Dereference the current address to get value
        printf("Value: %d\n", *ptr);

        // Move the pointer to the next integer block
        // (Jumps 4 bytes automatically)
        ptr++; 
    }
}

Comments

[Paul J. Lucas]

If ptr is a pointer to const, then end should likewise be a pointer to const.