sorting characters and output to text file

I'm a total newbie having trouble with an assignment for school. The assignment is asking me to write a program that reads the contents of a text file (characters), sort them alphabetically and output the results to a user defined text file. Do I need to use an array to accomplish this? As I said I'm new to C++ and we haven't even learned arrays yet so I'm not sure how to accomplish this assignment. Any help you can provide is greatly appreciated.

Thanks!

Below is the link to the assignment instructions:

http://www.cs.uwm.edu/classes/cs152/.../05/05/05.html

>>As I said I'm new to C++ and we haven't even learned arrays yet so I'm not sure how to accomplish this assignment.<<
http://www.cprogramming.com/tutorial/lesson8.html