  Let the circle group act on a 6-dimensional compact oriented manifold $M$
with isolated fixed points. The fixed point data of $M$ is the collection of
signs and weights at the fixed points. To classify such a manifold $M$, the
fixed point data is an essential information. Under an assumption that each
isotropy submanifold is orientable, we classify the fixed point data of $M$, by
showing that we can convert it to the empty collection by performing a
combination of a number of types of operations. We do so by proving that we can
successively take equivariant connected sums of $M$ at fixed points with $S^6$,
$\mathbb{CP}^3$, and 6-dimensional analogue $Z_1$ and $Z_2$ of the Hirzebruch
surfaces (and these with opposite orientations), to a fixed point free action
on a compact oriented 6-manifold.
