How Does Pointer Arithmetic Work in C/C ?

Pointer Arithmetic in C/C

In C and C , pointers are fundamental constructs used to manipulate memory addresses. Understanding pointer arithmetic helps programmers perform calculations and address data efficiently.

Pointer Subtraction

One aspect of pointer arithmetic involves subtracting two pointers. This operation is only valid for pointers pointing to elements of the same array or one past the last element. For instance, if an integer array array contains elements at addresses &array[0] to &array[7], the following operation would be valid:

ptr_diff_t diff = &array[5] - &array[2];

The result diff would be 3, representing the difference between the addresses of array[5] and array[2]. It's important to note that the returned type is ptrdiff_t, not int, because the result might be larger than the range of int.

Pointer Comparison

Pointer comparison is another important operation. In C and C , pointers can be compared using relational operators (<, >, ==, !=) if they point to the same array or aggregate object. The result of the comparison is true or false.

For example, if ptr1 and ptr2 point to elements of the same array, the following operation would return true if ptr1 points to a later element than ptr2:

bool greater = ptr1 > ptr2;

Similarly, ptr1 and ptr2 would be considered equal if they point to the same element.

It's crucial to understand that pointer comparison and arithmetic are only well-defined within the limits described by the C/C standards. Comparing or subtracting pointers that violate these rules may lead to undefined behavior.

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