SO file extension is for Shared object Fortran 90
Similar to SO
10X - Gemini 10x printer graphics file - Bitmap graphics123 - Lotus123 Data file
12M - Lotus123 Smartmaster file
15U - Printer font with PI font set PageMaker
1ST - Usually README.1ST text
24B - 24bit data Bitmap graphics
286 - Virtual device driver Windows standard mode
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