Why Do Arrays Start With Index Zero?

Recall the instance when you were introduced to the C programming language and were told that arrays in C start with index zero. I bet you wondered why 0! 🤔 Wouldn't be 1 a more obvious choice.

The Arrays in most programming languages(C, C++, Java, Python) start with index 0 instead of 1 and there are some surprising benefits of zero-based indexing for both compilers and programmers 😍.

Faster Compilation

In C, The name of an array is essentially a pointer to the starting address of contiguous memory allocated. Consider an array with starting address as 0x400.

int arr[5];

In Zero Based Indexing

To access the first element in array, arr[0] must be computed as *(arr + 0). Similarly, To access ith element in array, arr[i] must be computed as *(arr + i * sizeof(int)). It takes compiler 2 add operations to compute the address of ith element.

In One Based Indexing

The first element in array, arr[1] must be computed as *(arr + 1 - 1). Similarly,ith element in array, arr[i] must be computed as *(arr + (i - 1) * sizeof(int)). It takes compiler 3 add operation to compute the address of ith element.

Hence, It is efficient for the compiler to implement zero-based indexing ✌️.

Now, How many operations does it take to compute the address of arr[i][j]? I will leave it to you as an exercise ☺️, please respond in the comment section.

Programmer's Ease