Once you have initialized a ILOG CPLEX environment, your next step is to instantiate (that is, create and initialize) a problem object by calling CPXcreateprob(). This routine returns a C pointer to the problem object. Your application then passes this pointer to other routines of the Callable Library.

Most applications will use only one problem object, though ILOG CPLEX allows you to create multiple problem objects within a given ILOG CPLEX environment. Similarly, most applications create only one ILOG CPLEX environment, although ILOG CPLEX allows l environments, where l is the number of licensed ILOG CPLEX users on your system.