  We analyse a large number ($> 500$) pointed RXTE observations of Cyg X-1 and
model the spectrum of each one. A subset of the observations for which there is
simultaneous reliable measure of the hardness ratio by the All Sky Monitor,
shows that the sample covers nearly all the spectral shapes of Cyg X-1. The
relative strength, width of the Iron line and the reflection parameter are in
general correlated with the high energy photon spectral index $\Gamma$. This is
broadly consistent with a geometry where for the hard state (low $\Gamma \sim
1.7$) there is a hot inner Comptonizing region surrounded by a truncated cold
disk. The inner edge of the disk moves inwards as the source becomes softer
till finally in the soft state (high $\Gamma > 2.2$) the disk fills the inner
region and active regions above the disk produce the Comptonized component.
However, the reflection parameter shows non-monotonic behaviour near the
transition region ($\Gamma \sim 2$), suggestive of a more complex geometry or
physical state of the reflector. Additionally, the inner disk temperature,
during the hard state, is on the average higher than in the soft one, albeit
with large scatter. These inconsistencies could be due to limitations in the
data and the empirical model used to fit them. The flux of each spectral
component is well correlated with $\Gamma$ which shows that unlike some other
black hole systems, Cyg X-1 does not show any hysteresis behaviour. In the soft
state, the flux of the Comptonized component is always similar to the disk one,
which confirms that the ultra-soft state (seen in other brighter black hole
systems) is not exhibited by Cyg X-1. The rapid variation of the Compton
Amplification factor with $\Gamma$, naturally explains the absence of spectra
with $\Gamma < 1.6$, despite a large number having $\Gamma \sim 1.65$.
