Why use a for loop instead of a while loop?

Possible Duplicates:
Iterate with for loop or while loop?
Loops in C - for() or while() - which is BEST?

When should one use a for loop instead of a while loop?

I think the following loops are identical, except for their syntax. If so, then why choose one over the other?

int i;
for (i = 0; i < arr.length; i++) {
  // do work
}

int i = 0;
while (i < arr.length) {
  // do work
  i++;
}