There is only one file type that uses the .URCL extension:
URCL Assembly Source Code File
A URCL file contains Universal Reduced Computer Language (URCL) source code that can be compiled into machine code. It stores a set of instructions in plain text in URCL syntax.
You can compile a URCL file into machine code with various tools, such as URCL.NET or Haku's URCL framework.
You can also open and modify URCL files with source code and plain text editors. Microsoft Visual Studio Code (multiplatform) is a helpful source code editor that provides syntax highlighting capabilities (with the URCL plugin installed). You can also use Microsoft Notepad (Windows) or Apple TextEdit (macOS) to open and edit them, but these editors do not provide syntax highlighting.
Updated: July 27, 2020