Accessing external files, how?

Sorry about the nooby question, but I'm still working on that fraction calculator mentioned in the last thread, and I need to know how to do the following:

-> Make my program acess an external file
-> Check that the value of one of two variables don't match any in the external file.

Each line of the external file contains a number.

At the moment, the external file is a txt document, however it's easy enough to change.

Sorry about such a nooby question btw

Thx in advance,
-Cobrah

Use an object of class std::ifstream to open and read the file. I'm sure you will find a class reference and examples on the net (including this forum).