Is it necessary to initialize a variable under the while loop ?

Quote:

Is it necessary to initialize a variable under the while loop ?

Variable initialization is mandatory, everywhere, for every variables.
Variable initialization means that you must store a value in the variable before any attempt to use its contain.

while(i = 0 )

Here the initialization of i is misplaced because this place is for loop condition and the 0 will prevent from entering the loop.

i = 0;
while(i == 0)
   {
   ...
   }

This is probably what you want to do as suggested by OG.

a = 10;
while(i = a)
   {
   ...
   a--;
   }

but this is working because it means.

while((i = a) != 0)