We present the hard X-ray ( 20 - 100 keV ) observations of Cygnus X-1 obtained using a large area balloon-borne Xenon filled Multi-anode Proportional Counter ( XMPC ) telescope .
The observations were carried out during the \gamma _ { 2 } state of the source and we obtain a power law photon index of 1.62 \pm 0.07 .
To constrain the spectral shape of the source , we have analyzed the archival EXOSAT ME argon and GSPC data in the low energies ( 2 - 20 keV band ) as well as the archival OSSE data in the high energies ( 50 - 500 keV ) .
The data in different energy bands are not obtained in simultaneous observations , but they pertain to the \gamma _ { 2 } state of the source .
We have attempted a combined fit to the wide band data using appropriate mutual detector calibrations .
This method implicitly assumes that the variations in the source intensity in the \gamma _ { 2 } state is mainly due to the variations in the normalisations of the spectral components rather than any change in the spectral parameters .
A combined fit to the EXOSAT and XMPC data ( 2 - 100 keV ) shows that the observed spectrum requires a low energy absorption corresponding to the Galactic interstellar absorption , a low energy excess modeled as a blackbody , a narrow emission line due to iron K _ { \alpha } and a continuum .
The continuum can be either modeled as a power law with a reflection bump or a Comptonisation model with an additional bump which can be modeled as the partial covering with a heavy absorber .
To resolve between these two models , we have attempted a combined fit to the 2 - 500 keV data obtained from EXOSAT , XMPC and OSSE .
We find that a single Comptonisation model can not adequately represent the continuum .
The observed excess is at higher energies ( about 100 keV ) and it can not be modeled as reflection of power law or Comptonisation model .
We find that a two component Comptonisation model adequately represents the data .
We explore the possible emission region that is responsible for the observed spectrum .

\keywords X-rays : stars – stars : individual : Cyg X-1