MPE/iX, Multiprogramming Executive with Integrated POSIX,
is the latest in a series of forward-compatible operating systems
for the HP 3000 line of computers.
In HP documentation and in talking with HP 3000 users, you
will encounter references to MPE XL, the direct predecessor of MPE/iX.
MPE/iX is a superset of MPE XL. All programs written for MPE XL
will run without change under MPE/iX. You can continue to use MPE
XL system documentation, although it may not refer to features added
to the operating system to support POSIX (for example, hierarchical
directories).
Finally, you may encounter references to MPE V, which is the
operating system for HP 3000s, not based on the PA-RISC architecture.
MPE V software can be run on the PA-RISC HP 3000s (Series 900) in
what is known as compatibility mode.
