C | Pointer Basics | Question 6

#include<stdio.h>
int main()
{
    int arr[] = {10, 20, 30, 40, 50, 60};
    int *ptr1 = arr;
    int *ptr2 = arr + 5;
    printf("Number of elements between two pointer are: %d.",
                                (ptr2 - ptr1));
    printf("Number of bytes between two pointers are: %d",
                              (char*)ptr2 - (char*) ptr1);
    return 0;
}

Assume that an int variable takes 4 bytes and a char variable takes 1 byte
(A) Number of elements between two pointer are: 5.
Number of bytes between two pointers are: 20
(B) Number of elements between two pointer are: 20.
Number of bytes between two pointers are: 20
(C) Number of elements between two pointer are: 5.
Number of bytes between two pointers are: 5
(D) Compiler Error
(E) Runtime Error


Answer: (A)

Explanation: Array name gives the address of first element in array. So when we do ‘*ptr1 = arr;’, ptr1 starts holding the address of element 10. ‘arr + 5’ gives the address of 6th element as arithmetic is done using pointers. So ‘ptr2-ptr1’ gives 5. When we do ‘(char *)ptr2’, ptr2 is type-casted to char pointer and size of character is one byte, pointer arithmetic happens considering character pointers. So we get 5*sizeof(int)/sizeof(char) as a difference of two pointers.

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