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Such a message is usually the result of the compiler not being able to find the .mod file - the source file containing the module must first be compiled, which results in an object file (.o or .obj by extension) and a .mod file. This file must be found by the compiler for any source file that uses the module. Two reasons why it cannot be found:
- The source file which defines this module has not been compiled yet
- The .mod file is not in one of the directories where the compiler looks for such files.
You will need to check the compile options and the directory tree containing the sources etc. to determine which is the cause.