arch — Display the Architecture of the Current Host
/usr/bin/arch [-k | archname]
Systems can be broadly classified by their architectures, which define what executables run on which machines. You can make a distinction between kernel architecture and application architecture (or, commonly, just architecture). Systems that run different kernels because of underlying hardware differences may be able to run the same application programs.
arch displays the application architecture of the current host system. Because of extensive historical use of this command without any options, all SunOS 5.x SPARC-based systems return sun4 as their application architecture.
This command is provided for compatibility with previous releases ...