How to open/pop-up a text file from C++ code

I am making an exercise-logger program in C++. I have written the code for the login process, I just can't seem to figure out how to pop up their(that specific user's) log file. I want the program to open up the text file (in notepad) when the user has logged in. So that the user may see their previous workout logs. Is there a function in the standard file handling provided by C++?