| 61. | .biorad | Graphics (Biorad confocal file) |
| 62. | .bip | image file (band interleaved by pixel) (ArcView) |
| 63. | .bit | Bitmap graphics (X11) |
| 64. | .bix | Compressed file archive (BIX) |
| 65. | .biz | BizTalk compatible schema ◊ Business card (Broderbund, ProVenture) ◊ Geometry file (dVise) ◊ PMW BizCard Type |
| 66. | .bk | Faxbook (JetFax) |
| 67. | .bk! | Document backup (WordPerfect) |
| 68. | .bk$ | Backup file |
| 69. | .bk1 | Timed backup file for document window 1 (WordPerfect) |
| 70. | .bk2 | Timed backup file for document window 2 (WordPerfect) |
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