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Other duplicates of this thread:
http://cboard.cprogramming.com/c-programming/153947-urgently-need-help.html
http://cboard.cprogramming.com/c-programming/153944-sorting-c-language.html

You need to learn what a compiler is, and what it does, first by the sounds of it. Presumably you intend to use scanf or fgets to get the values from the user?
Then you'd use the function called...