I understand that for loops are used as
for(variable = value)(relational expression)(inc dec value) {loop}

my question is, do you have to increment or decrement the variable set at the first of the function? and do you even have to set a variable at all? Like could you just say..
for (i != 0) {loop that modifies i} ..or would that just be a for loop acting as a while loop.

I cant see a whole lot of uses for the for loop.. from what I see it's just a while loop with a preset number of loops.

could anyone give me a simple example of other uses for the for loop besides the plain for(i = 1)(i <=20) (i++)