If you invoke a procedure that has not been defined, FMSLogo first looks for a file in the current directory named
proc.lgo where "proc" is the procedure name in lower case letters.
If such a file exists, FMSLogo loads that file.
If the missing procedure is still undefined, or if there is no such file, FMSLogo then looks in the library directory for a file named proc (no ".lgo") and, if it exists, loads it.
If neither file contains a definition for the procedure, then FMSLogo signals an error.
Several procedures that are primitive in most versions of FMSLogo are included in the default library, so if you use a different library you may want to include some or all of the default library in it.