ADPCM file extension is for Intel/ DVI Adaptive Differential Pulse Code Modulation Sound format
Similar to ADPCM
$$P - OS/2 Notes file
$$S - OS/2 Spreadsheet
$00 - DOS Pipe file
$1 - ZX Spectrum file in HOBETA format
$D$ - Data
OS/2 Planner
$DB - Temporary file
dBASE IV
$ED - Editor temporary file
MS C
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