midl /<system> where <system> is one of: /win16 /win32 /mac /mips
/alpha /ppc /ppc32
midl /alpha filename.idl
Directs the MIDL compiler to generate a type library for the specified system.The default is the current operating system. The /mac switch directs MIDL to generate a type library for a 680x0-based Apple Macintosh system.
The /<system> switch is functionally the same as the MIDL /env option and is recognized by the MIDL compiler solely for backward compatibility with MKTYPLIB. If you are generating a new makefile, use the /env switch.
General MIDL Command-line Syntax, /env