Why pointers are known as non linear data structure?

Answer 1

Pointers are not structures, non-linear or otherwise. A pointer is a variable that holds a memory address. The primary operation that may be performed upon a pointer is the dereference operator, which allows indirect access to the value stored at the memory address held by the pointer variable. Pointer arithmetic may also be applied to pointers, such that the memory address stored in the pointer may be incremented or decremented in units equal to the size of the pointer's type. Thus a pointer to int where sizeof(int) is 4 would increment or decrement in units of 4 bytes. This pointer arithmetic makes it possible for a pointer to randomly access any element in a contiguous sequence of elements (such as an array) in constant time, thus allowing both linear and non-linear access to those elements. Pointers may also be used to provide links between elements that are stored non-contiguously, thus making it possible to create complex structures such as linked lists, trees, graphs and so on. This is achieved by using a node object to contain the element along with one or more links to other nodes in the sequence, both linearly and non-linearly.