Final answer:
The two main design standards for UNIX are POSIX and XPG, which facilitate compatibility and portability across different UNIX systems.
Step-by-step explanation:
The two main design standards to which most versions of UNIX adhere are POSIX and XPG. As UNIX developed, different organizations commercialized it, leading to a variety of proprietary and often expensive UNIX versions such as IBM's AIX, Microsoft's Xenix, Sun Microsystems' Solaris, and SGI's IRIX. POSIX (Portable Operating System Interface) is a family of standards specified by the IEEE for maintaining compatibility among various operating systems. XPG (X/Open Portability Guide) is a set of standards designed to ensure portability of applications across different UNIX systems. These standards helped establish common ground for the interface and behavior of UNIX systems and applications, fostering an environment where software could run on systems from different vendors.
The two main design standards to which most versions of UNIX adhere are POSIX and XPG. POSIX, which stands for Portable Operating System Interface, is a set of standards that define the application programming interface (API), shell commands, and utilities for compatibility between different operating systems. XPG, or X/Open Portability Guide, is another set of standards that addresses issues of compatibility and portability for UNIX systems.