Can someone explain what the EXP(X) function means?

My college professor gave us a math program assignment which gives you three options 1) Calculate X to the power of N 2) Calculate the factorial of N and 3) Calculate EXP(X) using the predefined function exp in C++

I have figured out the functions for the first two but am having trouble with the third. Our Book, Problem Solving with C++, however does not seem to go into detail about it. It just covers that EXP means e to the power of an x term. Could someone explain this better for me and give a general idea of what a function for this would be? Thanks