Your assignment is not a very hard one to do, infact it is a fairly standard assignment all you need to do is read carefully at whats asked and implement the code.
Read the following and it will teach you all you need to know to complete the assignment:
http://mycplus.com/tutorials/c-programming-tutorials/basic-dataypes-and-operators-in-c-programming/
http://mycplus.com/tutorials/c-programming-tutorials/file-handling/
http://mycplus.com/tutorials/c-programming-tutorials/arrays/
http://mycplus.com/tutorials/c-programming-tutorials/functions/
http://mycplus.com/tutorials/c-programming-tutorials/loops/
Good Luck :)