Why array index starts from 0(zero)?

Question

Hi,
I want to know, why array index starts from 0?

Answer 1

There is also another historical reason for this which often gets overlooked.
In machine language some instruction sets have a branch-on-zero instruction which would always come in very handy for saving CPU time in most kinds of loop.
These days you're used to forming your loops just as you like, which you could then, but a construct like
public class arraycopy {
     public static void main(String[] args)
          final int arraysize = 10;
          int[] i = new int[arraysize];
          int x;
          for (x = 0; x < arraysize; x++)
               i[x] = 25;
}effectively, each time the loop check is done, it compares i with arraysize and breaks if the condition fails. This program translates to...
LDA #$25
LDX #$00
LOOP STA $0200,X // <---- Note $0200 = arbitrary array location + X.
INX
CPX #$0A
BNE LOOP
In machine language (OOPS programmers will notice that the machine-language program is shorter, 12 bytes long in fact and it also executes much much faster).
Basically, the problem is, that CPX, the compare, takes time, almost 1/5 of the total execuation time, and in a small loop for a long array it eats clock cycles... and a couple of bytes (Tchoh!).
So, you can save time by re-writing the same loop thus...
LDA #$25
LDX #$0A
LOOP STA $01FF,X
DEX
BNE LOOP
By writing the loop backwards and taking advantage of the machine language underneath (i.e. the Real executable part of the program), you write a program that does exactly the same thing as the first example and is smaller and faster and easier to read. In fact the program takes 10bytes of memory. In machine-code you can place a complete working program in the amount of memory space it now takes you to store two double floats... now that's progress for you! : )
Python does it, C does it and I have been bemoaning the fact that Java doesn't ever since I began using it. I want to be able to start a loop:
while (x--)
For those who know the rule that all non-zero numbers are true, there is a multitide of new choices!
Join the revolution at
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6350717
: )