Simulation of a simple pendulum in Fortran using the semi-implicit Euler method

pendulum.f90

program pendulum
    implicit none

    real :: time, dt, g, l, y, v
    integer :: n, i

    read (*,*) time, dt, g, l, y, v
    n = ceiling(time / dt)

    do i=2,n
        v = v - (g/l * sin(y)) * dt
        y = y + v * dt

        print *, y
    end do
    
end program pendulum