GTKSourceView Language Definition for Tiny BASIC
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This file allows syntax highlighting for Tiny BASIC programs for any editor that supports GTKSourceView (two I know of are Mousepad and GEdit).
Download the file and stick it in your GTKSourceView directory, wherever that is (on my Linux system it's /usr/share/gtksourceview-3.0/language-specs). Restart your editor if necessary, and any .bas file you load should be properly highlighted.