If you want to do the opposite, starting from a number like 100 and count down to 1, the pattern will be similar.

You still have some variable tracking the current number, but with a loop whose condition is that the number is greater than the number you want to stop at, and a line at the bottom of the loop which decrements the current number.

~void main() {
int currentNumber = 100;
while (currentNumber >= 1) {
    IO.println(currentNumber);
    currentNumber--;
}
~}

Similar to when counting up if the condition was not currentNumber >= 1 and instead was currentNumber > 1, the loop would stop at 2

~void main() {
int currentNumber = 100;
// Stops at 2
while (currentNumber > 1) {
    IO.println(currentNumber);
    currentNumber--;
}
~}