program maximum
c This program finds the maximum value of a function on a grid.
c You may replace f(x) with your own function.
c The user inputs endpoints of an interval, and a grid size h;
c the program looks at all values of f(x) from x = a to x = b
c in steps of h, and picks the largest of these as the maximum.
real a, b, h, x, y, xmax, fmax, f
f(x) = cos(x) + 3 * sin(2 * x)
print *, "Enter the left endpoint :"
read *, a
print *, "Enter the right endpoint :"
read *, b
print *, "Enter the gridsize :"
read *, h
x = a
xmax = a
fmax = f(a)
do while (x .lt. b)
y = f(x)
if (y .gt. fmax) then
xmax = x
fmax = y
end if
x = x + h
end do
print *
print *, "The maximum value was found at x = ", xmax
print *, "The function value there is ", fmax
print *
print *, "Auf Wiedersehen"
end