PC-DOS 360K format
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| − | The '''PC-DOS 360K format''' was a very common floppy disk format in the 1980s, used on IBM PCs and compatibles. It replaced earlier [[PC-DOS 160K format|160K]], [[PC-DOS 180K format|180K]], and [[PC-DOS 320K format|320K]] formats using either fewer sectors, single-sided disks, or both, with a new format getting the most out of a double-sided, double-density 5 1/4" floppy disk. It had 40 tracks per side, with 9 sectors per track, and 512 bytes per sector | + | The '''PC-DOS 360K format''' was a very common floppy disk format in the 1980s, used on IBM PCs and compatibles. It replaced earlier [[PC-DOS 160K format|160K]], [[PC-DOS 180K format|180K]], and [[PC-DOS 320K format|320K]] formats using either fewer sectors, single-sided disks, or both, with a new format getting the most out of a double-sided, double-density 5 1/4" floppy disk. It had 40 tracks per side, with 9 sectors per track, and 512 bytes per sector. The disk turned at 300 RPM. |
| − | These disks were generally used with [[FAT12]] file systems under the MS-DOS or PC-DOS operating system. | + | These disks were generally used with [[FAT12]] file systems under the MS-DOS or PC-DOS operating system, but (far more rarely) were used with other filesystems too (e.g CP/M-86). The sector headers, etc, were based on [[IBM 3740]] format, albeit with [[MFM encoding]] (double density) replacing the original [[FM encoding]] (single density). |
After being a commonplace format for most of the 1980s, this format declined in favor of the high-density [[PC-DOS 1.2M format]] and the 3 1/2" [[PC-DOS 720K format]] and [[PC-DOS 1.44M format]]. (There were compatibility issues in reading 360K disks on low-density drives after they were written to with a high-density drive, even though the writing is done in an emulation of the old format, due to the different drive head on the newer drives. The high-density drive heads were smaller, and the data written by them might not be picked up correctly by the larger low-density heads, particularly if the new data was overwriting data stored earlier using large-headed drives, which might not be completely overwritten.) | After being a commonplace format for most of the 1980s, this format declined in favor of the high-density [[PC-DOS 1.2M format]] and the 3 1/2" [[PC-DOS 720K format]] and [[PC-DOS 1.44M format]]. (There were compatibility issues in reading 360K disks on low-density drives after they were written to with a high-density drive, even though the writing is done in an emulation of the old format, due to the different drive head on the newer drives. The high-density drive heads were smaller, and the data written by them might not be picked up correctly by the larger low-density heads, particularly if the new data was overwriting data stored earlier using large-headed drives, which might not be completely overwritten.) | ||
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* [http://www.textfiles.com/programming/FORMATS/formats.pro Info on MS-DOS 1.x - 2.x disk formats] | * [http://www.textfiles.com/programming/FORMATS/formats.pro Info on MS-DOS 1.x - 2.x disk formats] | ||
* [http://67.185.176.54:8080/diskette_handling.html Working with old diskettes] | * [http://67.185.176.54:8080/diskette_handling.html Working with old diskettes] | ||
| + | * [http://www.computerhistory.org/_static/atchm/microsoft-ms-dos-early-source-code/ Early PC-DOS source code] | ||
[[Category:IBM]] | [[Category:IBM]] | ||
[[Category:Microsoft]] | [[Category:Microsoft]] | ||
| + | [[Category:MS-DOS]] | ||
Latest revision as of 10:30, 5 September 2024
The PC-DOS 360K format was a very common floppy disk format in the 1980s, used on IBM PCs and compatibles. It replaced earlier 160K, 180K, and 320K formats using either fewer sectors, single-sided disks, or both, with a new format getting the most out of a double-sided, double-density 5 1/4" floppy disk. It had 40 tracks per side, with 9 sectors per track, and 512 bytes per sector. The disk turned at 300 RPM.
These disks were generally used with FAT12 file systems under the MS-DOS or PC-DOS operating system, but (far more rarely) were used with other filesystems too (e.g CP/M-86). The sector headers, etc, were based on IBM 3740 format, albeit with MFM encoding (double density) replacing the original FM encoding (single density).
After being a commonplace format for most of the 1980s, this format declined in favor of the high-density PC-DOS 1.2M format and the 3 1/2" PC-DOS 720K format and PC-DOS 1.44M format. (There were compatibility issues in reading 360K disks on low-density drives after they were written to with a high-density drive, even though the writing is done in an emulation of the old format, due to the different drive head on the newer drives. The high-density drive heads were smaller, and the data written by them might not be picked up correctly by the larger low-density heads, particularly if the new data was overwriting data stored earlier using large-headed drives, which might not be completely overwritten.)
In the late '80s and early '90s, it was common for desktop PCs to have both 5 1/4" and 3 1/2" disk drives in order to be compatible with all software and data, which might be distributed on either format. Often the 5 1/4" drive was drive A, and the 3 1/2" one was drive B. Later PCs, however, were more likely to have only a 3 1/2" drive, set up to respond to both drive letters. Eventually, PCs stopped having floppy disk drives altogether as other data storage and transfer media took over.
