i is just a counter for the loop. The for statement means the loop will execute 7 times. It's a perfectly good way of performing a repeated action. Why do you want to change it?
for statements are one of the absolutely fundamental building blocks of C/C++ coding. If you're going be working with code at all, I strongly recommend you go back to your tutorial sources and learn about them.
Count down instead of up (this can also be slightly quicker too)
What is your reasoning for this? I don't see how it could be any quicker since addition and subtraction take the same amount of time and you are still going through the same iterations, just in a different order. Grated, there might be rare cases where it is faster due to branch prediction, but the same is just as likely for increasing.
:) I actually found loops counting down will still be slightly faster even with modern compilers, but I work on high speed computing where 1 second of time saved per iteration equates to about 11 days saved real time.