| Abbreviation | Definition |
|---|---|
| SIG | Signature file |
| SIG | Signature file of Current program settings |
| SIK | Sicherungskopie Backup file |
| SIM | Telix SIMPLE script source |
| SIR | Solitaire file Bitmap graphics |
| SIS | Psion Software Installation file |
| SIS | Scanscope Image Set |
| SIT | UnStuff Compressed file archive |
| SIX | Sixel file Bitmap graphics |
| SIXEL | Sixel file Bitmap graphics |
| SKCARD | SideKick Datafile |
| SKD | Schedule |
| SKD | SSEYO Koan Design file |
| SKM | SSEYO Koan Mix files |
| SKP | SSEYO Koan Play file |
| SKR | PGP Secret Keyring |
| SKT | SSEYO Koan Template file |
| SKY | SYLK Spreadsheet file |
| SL | S-Lang language source code file |
| SLB | P-CAD Symbols library |