Some questions about Opening / Saving file from me

I am a newbie in OpenGL. I want to make some user interface so that “Open” button can load any chosen file from directory and then open the file to process the data. In the same way, when the user presses the save button, file can be saved with a given name. I am not much familiar with GUI. Could any one tell me the simplest approach?
Thanks in advance for your cooperation.