On Solaris you can find out the supported programming model(s) using isainfo.

There are a number of other options including the -b option prints the number of bits in the address space of the native applications environment.

On current UNIX systems the programing model is typically either IPL32 or LP64. In the mid-1990s, the Aspen WG agreed on the LP64 programming model and produced a paper which will help you understand the various programming models.

64-BIT PROGRAMMING MODELS

For further information on UNIX programming models Google is your friend!