In my C program I want a user to enter a formula, such as an equation of a line in a graph. As of now I have the data entered going into an array. In every event that the user enters an "x" i want to submit a variable into. For example: If the user enters: x*x+x-2, I would like to take that input and put in different values for every time he or she entered "x". Any idea how? Or do you need more information/detail? Thanks.