Because the AIMS architecture uses generic building blocks, a need existed for multiple software applications to be able to share common hardware resources, without corrupting each other’s data. This led to the development of Honeywell’s Apex operating system–with its time and space partitioning–which became the foundation for the ARINC 653 operating system spec. Under Apex, for example, the central maintenance function (Level D of DO-178B), flight deck communications (Level C) and DCG (Level A) can share the same processing hardware yet still be developed and verified independently.