The  Mach  3.0  micro-kernel provides the following functions: virtual memory
management, inter-process communication, tasks, threads, exceptions, scheduling
primitives and device drivers.

  It  does  not  provide  a file system, tty i/o, network support or other Unix
features like signal and Unix tasks. The pure kernel alone does not give you  a
usable operating system.

  The  ftp distribution consists of the following directories containing kernel
sources, kernel/:

boot_ufs:       A minimal file system that is used when booting and paging on a
                disk-based file system. Reads a Mach 2.5/BSD 4.3 file system.

conf:           Contains all the configuration files for building the kernel.

ddb:            A  debugger  built  into  the  kernel  with  a  dbx  style user
                interface.  See the man page in man/ddb.man  for  its  use.  It
                will be loaded with the kernel if the debug option is chosen.

device:         Files that implement the device interface of the Mach kernel.

i386:           Files specific to the i386 architecture.

i386at:         Files that implement i386 device drivers for an atbus machine.

intel:          Pmap code that is common between i386 and i860 based machines.

ipc:            Files that implement the ipc functionality of the kernel.

kern:           Files  that  implement  tasks, threads, scheduling, exceptions,
                timing, kernel memory allocation, et.al.

mach:           The header files  that  define  the  machine  independent  user
                interface to the Mach kernel.

mach/i386:      The  header  files that define the i386 specific user interface
                to the Mach kernel.

mach/i860:      The header files that define the i860 specific  user  interface
                to the Mach kernel. (The i860 sources are not available by ftp)

mach/mips:      The  header  files that define the mips specific user interface
                to the Mach kernel.

mach/sun3:      The header files that define the sun3 specific  user  interface
                to the Mach kernel. (The sun3 sources are not available by ftp)

mach/vax:       The header files that define the vax specific user interface to
                the Mach kernel.  (The vax sources are not available by ftp)

mach_debug:     The  header  files  that  define  the  user  interface  to  the
                debugging  facilities  of the Mach kernel. These interfaces are
                only available in kernels  with  various  levels  of  debugging
                options turned on: eg. debug, ipc_debug, vm_debug.

man:            man pages for some of the Mach 3.0 kernel interfaces.

mips:           Files specific to the mips R2000/3000 architecture.

mips/PMAX:      File that implement drivers for the DecStation 3100/5000.

mips/PMAX/boot: Files to build the boot program for the DecStation 3100/5000.

src/config:     Files  to  build  the config program that is used when building
                the kernel.

src/mig:        Files to build the migcom program that is used to generate Mach
                rpc  interfaces  to  ipc  calls.  Migcom  is used during kernel
                builds.

sys:            A few header files defining interfaces left over from 3.4 BSD.

vm:             Files that implement machine independent virtual memory.

  There is also one other directory:

user/libmach:   Contains library routines that are need by the  kernel  or  the
                mig  program.  This  is  a  temporary  arrangement  and will be
                replaced by a more complete library in a different area as soon
                as it is available.