what does ":U" mean?

The "string":U means keep the format EXACTLY as is what ever the local (session/instance) language definitions are.
It is informing the prowin32 / wotever, compiler that Progress is NOT to mess with the string.
 
In fact, this is a matter of translation. In Progress Words ... (See the Progress Internationalisation Guide)

4.1.4 Coding With Translation In Mind​
Progress includes, as an option, the Translation Management System, a product that supports the translation of Progress applications. The Translation Management System extracts translatable strings from your application code and presents them to the translator. To use the
Translation Management System on your code, you must mark untranslatable strings with :U, as the following example shows:
The :U following the string​
GUImarks the string as untranslatable, and the Translation
Management System does not include it in a translation database.
The code that the Progress AppBuilder generates also follows this convention. That is, AppBuilder puts :U after each string not to be translated.

 
Back
Top