C4 file extension is for 1bit JEDMICS CCITT Group 4 format Bitmap graphics
Similar to C4
#GF - MetaFont Font file
#IB - LocoScript Printer data file
#SC - LocoScript Printer data file
#ST - LocoScript Standard mode printer definition file
$$P - OS/2 Notes file
$$S - OS/2 Spreadsheet
$00 - DOS Pipe file
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