design from the beginning, influenced by notions of the designers of the 6809 and how they expected software would be distributed in the future (see the three-part series of articles in January-March 1979 Byte by Terry Ritter, et al. of Motorola who designed the CPU). The module structure requires more explanation: OS-9 keeps a "module directory", a memory-resident list of all modules that are in memory either by having been loaded, or by having been found in ROM during an initial scan at boot time. When one types a command to the OS-9 shell, it will look first in the current module directory for a module of the specified name and will use it (and increase its link count) if found, or it will look on disk for an appropriately named file if not. In OS-9/6809 and OS-9/68000, the module directory is flat, but OS-9000 made the module directory tree-structured. The OS-9000 shell looks in one's alternative module directory for a MODPATH environment variable, analogous to the PATH variable in all versions, indicating the sequence of module directories in which to look for pre-loaded modules. Modules are not only used to hold programs, but can also be created on the fly to hold data, and are the way in which OS-9 supports shared memory. OS-9/non-68000 supports POSIX threads. A single process can start any number of threads. Status OS-9 has faded from popular use, though Microware LP does still support it and it does run on modern architectures such as ARM and x86. The compiler provided, Ultra C/C++, supports C89, but supports neither C99 nor C++98. Ultra C++ does provide limited support for C++ templates. It is also supported by popular SSL/TLS libraries such as wolfSSL. A Version of OS-9 running Steve Adams' G-Windows is present on semiconductor wafer scrubbers manufactured by Ontrak Systems / Lam Research. Thousands of these systems are in use today, however, the software running on them dates to 1999 when the last version was created to handle Y2K issues. Versions of OS-9/68K ran on a wide variety of 68000 family platforms, including the Sharp X68000 in Japan, some personal computers intended by their designers as upgrades from the Color Computer (e.g., the 68070 and 68340-based MM/1, and on other computers from Frank Hogg Laboratories, PEP Modular Computers, and Delmar Co.) It was also ported to the Atari ST by Recc-o-ware in the early 1990s, and