  This paper is the manual of the CompOSE service, see http://compose.obspm.fr,
an equation of state (EoS) database for use in nuclear physics and in
astrophysical applications, e.g. the simulation of core-collapse supernovae and
compact stars. The main aims of the service are the following: to offer a
robust, easily extendable data format to store and read EoS data tables and
related physical quantities; to make these data available to the public --
respecting the original work by the contributors -- in a standard format
designed for easy access and flexibility; and to provide routines to
interpolate these data in the parameter space of density, temperature and
hadronic charge fraction. The manual contains a detailed description of the
service. It is divided into three parts, containing a general introduction as
well as instructions for potential contributors and for users.
