Editing File Allocation Table (section)

=== <span id="FAT8"></span><span id="FAT10"></span>Original 8-bit FAT ===
<!-- NB. "FAT8" and "FAT10" are used as handy invisible anchors, but they never were the official names for these FAT variants, and therefore must not be used in the visible text. -->
{{infobox file system
| name = 8-bit FAT
| full_name = 8-bit File Allocation Table
| developer = [[Microsoft]], [[NCR Corporation|NCR]], [[Seattle Computer Products|SCP]]
| variants = 
| introduction_date = {{ubli
 | 1977/1978: [[NCR Basic +6]] for NCR
 | 1978: [[Standalone Disk BASIC-80]] (16-byte directory entries)<ref name="Microsoft_1979_BASIC80-50" /><ref name="Microsoft_1979_BASIC80-51" />
 | (1978: [[Standalone Disk BASIC-86]] internal only)
 | 1979-06-04: [[Standalone Disk BASIC-86]] for SCP (16-byte directory entries)
 | 1979: [[MIDAS (operating system)|MIDAS]] (32-byte directory entries)
 }}
| partition_id = 
| directory_struct = 
| file_struct = 
| bad_blocks_struct = 
| max_volume_size = <!-- TBD -->
| max_file_size = 8 MB
| max_files_no = <!-- TBD -->
| max_filename_size = [[6.3 filename]]<!-- displayed with decimal dot as "123456.789" --> (binary files), 9&nbsp;characters<!-- displayed with space as "123456 789" --> (ASCII files)<ref name="Microsoft_1979_BASIC80-50" /><ref name="Microsoft_1979_BASIC80-51" />
| max_directory_depth = No sub-directories
| dates_recorded = No
| forks_streams = 
| attributes = Write protected, [[EBCDIC]] conversion, read after write, binary (random rather than sequential file)<ref name="Microsoft_1979_BASIC80-50" /><ref name="Microsoft_1979_BASIC80-51" />
| file_system_permissions = 
| compression = 
| encryption = 
| data_deduplication = 
| OS = 
| filename_character_set = [[ASCII]] (<code>0x00</code> and <code>0xFF</code> not allowed in first character)<ref name="Microsoft_1979_BASIC80-50" /><ref name="Microsoft_1979_BASIC80-51" /><!-- In reality, character set is most probably more limited due to BASIC language restrictions. -->
| file_size_granularity = record-granularity (128&nbsp;bytes<!-- 256 bytes for mini-disks? -->)<ref name="Microsoft_1979_BASIC80-50" /><ref name="Microsoft_1979_BASIC80-51" />
}}
The original FAT file system (or ''FAT structure'', as it was called initially) was designed and implemented by [[Marc McDonald]],<ref name="Duncan_1988_MS-DOS_Encyclopedia" /> based on a series of discussions between McDonald and [[Bill Gates]].<ref name="Duncan_1988_MS-DOS_Encyclopedia" />
It was introduced with [[8-bit]] table elements<ref name="Microsoft_1979_BASIC80-50" /><ref name="Microsoft_1979_BASIC80-51" /><ref name="Duncan_1988_MS-DOS_Encyclopedia" /> (and valid data cluster numbers up to <code>0xBF</code><ref name="Microsoft_1979_BASIC80-50" /><ref name="Microsoft_1979_BASIC80-51" />) in a precursor to [[Microsoft]]'s ''[[Standalone Disk BASIC-80]]'' for an [[Intel 8080|8080]]-based successor<ref group="nb" name="NB_NCR_FAT" /> of the [[NCR 7200 model VI]]<!-- model I and IV did not came with BASIC, whereas the still cassette-based model VI did in Q1/1977 --> data-entry terminal, equipped with 8-inch (200&nbsp;mm) floppy disks, in 1977<ref name="Manes_1993_Gates" /> or 1978.<ref group="nb" name="NB_NCR_FAT" />
In 1978, ''Standalone Disk BASIC-80'' was ported to the [[Intel 8086|8086]] using an emulator on a DEC [[PDP-10]],<ref name="Hunter_1983_Softalk" /> since no real 8086 systems were available at this time.
The FAT file system was also used in Microsoft's [[MIDAS (operating system)|MDOS/MIDAS]],<ref name="Duncan_1988_MS-DOS_Encyclopedia" /> an [[operating system]] for 8080/Z80 platforms written by McDonald since 1979.
The ''Standalone Disk BASIC'' version supported three FATs,<ref name="Microsoft_1979_BASIC80-50" /><ref name="Microsoft_1979_BASIC80-51" /><ref name="Schulman_1994_Undocumented-DOS" /> whereas this was a parameter for MIDAS. Reportedly, MIDAS was also prepared to support 10-bit, 12-bit and 16-bit FAT variants. While the size of directory entries was 16 bytes in ''Standalone Disk BASIC'',<ref name="Microsoft_1979_BASIC80-50" /><ref name="Microsoft_1979_BASIC80-51" /> MIDAS instead occupied 32&nbsp;bytes per entry.

[[Tim Paterson]] of [[Seattle Computer Products]] (SCP) was first introduced to Microsoft's FAT structure when he helped [[Bob O'Rear]] adapting the ''[[Standalone Disk BASIC-86]]'' emulator port onto SCP's [[S-100 bus]] 8086 [[Central processing unit|CPU]] board prototype during a guest week at Microsoft in May 1979.<ref name="Hunter_1983_Softalk" /> The final product was shown at [[Lifeboat Associates]]' booth stand at the [[National Computer Conference]] in New York<ref name="Hunter_1983_Softalk" /> on June 4–7, 1979, where Paterson learned about the more sophisticated FAT implementation in MDOS/MIDAS<ref name="Duncan_1988_MS-DOS_Encyclopedia" /> and McDonald talked to him about the design of the file system.<ref name="Manes_1993_Gates" />