THINK++ — Engineering Visualized

Implicit Decay

Pointers & Arrays

In C++, the name of an array acts as a pointer to its first element. This close relationship is why pointer arithmetic works so well with arrays.

THE EQUIVALENCE

int arr[5] = {10, 20, 30, 40, 50};
int* ptr = arr; // ptr points to arr[0]

cout << arr[0];   // 10
cout << *arr;     // 10 (Implicitly a pointer!)
cout << *(arr+1); // 20 (Same as arr[1])

ARRAY NOTATION

arr[i]

The compiler actually translates this to pointer arithmetic under the hood.

POINTER NOTATION

*(arr + i)

This is what happens internally: base address + offset.

ONE KEY DIFFERENCE

An array name is a CONSTANT pointer. You cannot change its address (arr++ is illegal). A regular pointer can be reassigned freely.

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Pointers And Arrays

Pointers And Arrays

Pointers & Arrays

Pointers & Arrays