Improved Euler's method

The classical improved or modified version of the simple Euler's method in evaluating 1st order ODEs

It is the classical Improved or modified version of Euler's method, an iterative approach in finding the y value for a given x value starting from a 1st order ODE. It asks the user the ODE function and the initial values and increment value. It also lets the user choose what termination criterion to use, either a specified x value or a number of iterations. If the solution curve for the given ODE is readily available, the user can input it and have the true %relative error.