The micro variety, examples of which include L4 or the Carnegie Mellon developed Mach, often handle interprocess communication by message passing or delegating to the MMU, as 
The micro variety, examples of which include L4 or the Carnegie Mellon developed Mach, often handle interprocess communication by message passing or delegating to the MMU, as opposed to the monolithic type, which shares process memory. Common features usually include an API, an interrupt request or call gate ability, I/O device management and thread scheduling. Linus Torvalds famously got in an extended debate over the nature of Linux's, and Mac OS X's XNU is an example of, for 10 points, what operating system component that provides a layer of abstraction between programs and the hardware.
The micro variety, examples of which include L4 or the Carnegie Mellon developed Mach, often handle interprocess communication by message passing or delegating to the MMU, as opposed to the monolithic type, which shares process memory.
{Kernel}