Question

Which arithmetic operations can be applied to pointers?

Short answer

A. Addition B. Subtraction C. Multiplication D. Division Answer: A (Addition) and B (Subtraction).

Step-by-step solution

Understanding pointers

A pointer is a variable that stores the memory address of another variable or object. Pointers are essential in various programming tasks, such as dynamic memory allocation, manipulating arrays, and implementing data structures.

Pointer arithmetic and limitations

Pointer arithmetic is the process of adding or subtracting an integer value to/from a pointer to move the pointer to a new address, usually relating to an array's elements. Note that not all arithmetic operations can be applied to pointers. We will go through each operation and provide an example of its use or prohibition.

1. Addition

Addition is a valid operation for pointers. When adding an integer value to a pointer, the pointer moves forward by a number of elements equal to the integer value. Example in C: ```c int arr[] = {1, 2, 3, 4, 5}; int *p = arr; // p points to the first element of arr p = p + 2; // p now points to the third element of arr ```

2. Subtraction

Subtraction is also a valid operation for pointers. When subtracting an integer value from a pointer, the pointer moves backward by a number of elements equal to the integer value. Example in C: ```c int arr[] = {1, 2, 3, 4, 5}; int *p = arr + 4; // p points to the last element of arr p = p - 2; // p now points to the third element of arr ```

3. Multiplication

Multiplication is not a valid operation for pointers. Trying to multiply a pointer by a scalar will result in a compile-time error. Example in C: ```c int arr[] = {1, 2, 3, 4, 5}; int *p = arr; p = p * 2; // This line will cause a compile-time error ```

4. Division

Similarly, division is not a valid operation for pointers. Trying to divide a pointer by a scalar will result in a compile-time error. Example in C: ```c int arr[] = {1, 2, 3, 4, 5}; int *p = arr; p = p / 2; // This line will cause a compile-time error ```

5. Comparisons

Comparisons between two pointers are valid operations, such as checking if one pointer is less than, equal to, or greater than another pointer. This can be useful when comparing two pointers within the same array. Example in C: ```c int arr[] = {1, 2, 3, 4, 5}; int *p1 = arr; int *p2 = arr + 3; if (p1 < p2) { printf("p1 comes before p2 in the array.\n"); } ```

Summary

In conclusion, among the arithmetic operations, only addition and subtraction can be applied to pointers, mainly when working with arrays. Multiplication and division with pointers are not allowed. Comparisons between pointers are valid operations.