Input from microphone real time

I would like to make an application that took the microphone input (via jack) I would like to change the signal by applying an effect (for example by changing the frequencies Low, Mid or Hight) and then send any output in the headphones (always through jack). All in REAL TIME.

I would like to know:

-How to take the signal from the microphone input jack and send it back in the headphones?

-How do I change the sound (eg changing frequencies Low, Mid or Hight)?

Any help is welcome