MI, W-Code and OS/400

["Joe Pluta" <joepluta@xxxxxxxxxxxxxxxxx>]

> Steve Richter wrote:
>
> Is W-Code lower level than MI?

I won't get into the argument about translating W-Code to C.  However, I
will outline the architecture really quickly:

1. MI is the lowest machine-independent layer of OS/400 software.  Below
that (at this level I get a little fuzzy) is a machine-dependent layer that
must be rewritten for each new processor.

2. There are two flavors of MI, original MI (OMI) and new MI (NMI).
Basically, NMI is OMI with certain extensions designed to better support
W-Code.

3. OPM programs are translated to OMI, which is then converted to NMI.

4. ILE programs are translated to W-code, which in turn is converted
directly to NMI.  RPG, COBOL, CL, C and C++ all have ILE compilers.  Also,
CRTJVAPGM converts Java bytecodes to NMI.

The NMI is then subject to MASSIVE amounts of optimization when being
finally translated to executable code.  When I did some research on the
optimizer, my brain nearly exploded.  But that's just me.

Joe