% Simple present value calculation program

var R : real
var i : real
var n : real
var c : real
var res : real

% Set values up here
R := 800 % amount of the monthly investment, in dollars
i := 0.2 % compound percentage
n := 7 % period of time (years)
c := 1 % compound frequency

% Calculate crap. This has been split over two lines to reduce complexity
res := R * ((1 - (1 + (i / c)) * exp (-n * c)))
res := res / (i / c)

put "Result is ", res