difference between while,dowhile and for loop? which loop is best?

I like using the for loop when I want something to loop a known no. of times and when I have indices or pointers that I want to increment or decrement with each loop. Its useful for going through strings or arrays.

A while loop is good for when you want something to loop as long as some condition is true, even indefinitely, and/or if you want something that won't loop at all if the condition is false to start. This is because the test condition is tested at the begining of the loop.

A do while differs from the while in that it will execute once even if the condition is false to start with. This is because the condition is tested at the end of the loop.

Of course it depends on what you want the code to do as each of these can be used in various ways. A for loop can have no increments or starting values and just operate like a while. Or a while loop can have indices counting inside the loop that get tested at the end.

And don't forget you can use break and continue statements. Break exits out of a loop at any point, and continue jumps over any statements after it in the loop and continues looping.