Sounds like you're trying to do a school project of some sort? Member rules state "Do not post homework problems expecting a quick answer without showing any effort yourself." You've told us little about details. What language are you using? What OS? Do have have ANY code written? I'm brand new to this board myself so I'm sure others might be tighter on the rules that I might be- and this part of the forum probably isn't the most appropriate place to post this question. But I'm sympathetic and will provide a tidbit to get you thinking.
Won't give it away w/ code- but I would imagine creating an array of 100 entries and only using, say, 10, would be sufficient. (hint: make sure the 'unused' entries don't contain values).