Hey, I am somewhat new to C++.
I'm not sure if this is something that is even possible with this programming language, but I am very curious.
Okay, so the gist of what I want to do, is be able have an input through the microphone jack on the sound card. Then, I would like to have a c++ program that could show, with numbers, the frequency of the noise being played into the microphone. i.e. Guitar, or other instrument through a microphone.
Could anyone at least point me in the right direction?

Finding a library which does this for you would be a really good idea.

Essentially, you want to take your sample set, which is in the time domain, and turn it into something in the frequency domain.

As for recording your sample, state your OS and compiler for more specific information.