| Abbreviation | Definition |
|---|---|
| XX | XXdecode - XXencode Encoded file archive ( ASCII) |
| XXE | XXencode Encoded file archive ( ASCII) |
| XY | XY Write Text document |
| XY3 | XYWrite III Text document |
| XY4 | XYWrite IV Text document |
| XYP | XYWrite III Plus Text document |
| XYW | XYWrite for Windows Text document |
| Y | Subsampled raw YUV file Bitmap graphics |
| Y | YACC Grammar file |
| Y01 | Paradox Secondary index |
| Y02 | Paradox Secondary index |
| Y03 | Paradox Secondary index |
| Y04 | Paradox Secondary index |
| Y05 | Paradox Secondary index |
| Y06 | Paradox Secondary index |
| Y07 | Paradox Secondary index |
| Y08 | Paradox Secondary index |
| Y09 | Paradox Secondary index |
| YAL | Clipart library - Arts & Letters |
| YBK | Microsoft Encarta Yearbook |