O/S interoperability commands and functions

Functioning occurs at the Windows O/S level, which imposes its own rules and constraints, such as:

• The uopen command and ucreate command return a Windows file-handle. These are a limited resource and must be released explicitly.
• The variable returned by the uexecute command, and used by the uwaitfor command or the umessage command, is also a Windows file-handle. Changing the variable, and then feeding the result to the uwaitfor command or the umessage command could cause unpredictable results.