(1) For i5/OS, the layered architecture below the machine interface (MI). The Licensed Internal Code is a proprietary system design that carries out many functions. These functions include but are not limited to storage management, pointers and addressing, program management functions, exception and event management, data functions, I/O managers, and security.
(2) Microcode that IBM does not sell as part of a machine, but licenses to the customer. LIC is implemented in a part of storage that is not addressable by user programs. Some IBM products use it to implement functions as an alternative to hardware implementations.