integer, parameter :: N = 1000
real :: x(N), y(N), dx
integer :: i
dx = (3.0-(-3.0)) / (1.0*N)
open( 1, file = 'data.txt' )
do i = 1, N
x(i) = -3 + i * dx
y(i) =x(i)*x(i)
write(1,*) x(i), y(i)
end do
close( 1 )
end