All ILOG CPLEX applications either call the routine CPXopenCPLEX to establish the CPLEX environment, or use the appropriate constructor (IloCplex in the C++ and Java API or Cplex in the .NET API) to initialize ILOG CPLEX for use with Concert Technology. Until either CPXopenCPLEX is called or the IloCplex object exists, few ILOG CPLEX routines or methods operate. In addition to allocating the environment, CPXopenCPLEX performs license checks, as do the constructors for Concert Technology. For development licenses, no additional licensing steps are required. For runtime licenses, your application first needs to provide some additional licensing information before the call to CPXopenCPLEX or the use of a constructor.

Documentation of the routines CPXputenv and CPXRegisterLicense is in the ILOG CPLEX Callable Library Reference Manual; documentation of IloCplex.putenv and IloCplex.registerLicense is in the ILOG CPLEX Java API Reference Manual; documentation of Cplex.PutEnv and Cplex.RegisterLicense is in the ILOG CPLEX .NET API Reference Manual.