Question

First code:

  if(i==0) {// do instructions here}

Second code:

  if(0==i) { // do instructions here }

What is the difference between the blocks?

Answer 1

Functionally, there is no difference.
Some developers prefer writing the second format to avoid assignment typos(in case you miss a =), so that compiler warns of the typo.
The second is famously known as Yoda Condition.

I say there is no difference because, you cannot guard yourself against every minuscule detail and rely on compiler to cry out aloud for you.If you intend to write a == you should expect yourself to write a == and not a =.
Using the second format just leads to some obscure non-readable code.
Also, most of the mainstream compilers warn of the assignment instead of equality typo by emitting an warning once you enable all the warnings(which you should anyways).