'[RC] Runge-Kutta method
'initial conditions
x0 = 0
y0 = 1
'step
h = 0.1
'number of points
N=101

y=y0
FOR i = 0 TO N-1
    x = x0+ i*h
    IF x = INT(x) THEN
        actual = exactY(x)
        PRINT "y("; x ;") = "; y; TAB(20); "Error = ";  actual - y
    END IF

    k1 = h*dydx(x,y)
    k2 = h*dydx(x+h/2,y+k1/2)
    k3 = h*dydx(x+h/2,y+k2/2)
    k4 = h*dydx(x+h,y+k3)
    y = y + 1/6 * (k1 + 2*k2 + 2*k3 + k4)
NEXT i

function dydx(x,y)
    dydx=x*sqr(y)
end function

function exactY(x)
    exactY=(x^2 + 4)^2 / 16
end function