Editing 86-DOS (section)

==Features==

===Commands===
The following list of [[command (computing)|commands]] is supported by 86-DOS.<ref name="SCP_1980_86-DOS-UM"/>

====Internal commands====
{{div col|colwidth=9em}}
* CLEAR
* [[COPY (DOS command)|COPY]]
* [[DIR (DOS command)|DIR]]
* [[DEL (DOS command)|ERASE]]
* [[REN (DOS command)|RENAME]]
* [[TYPE (DOS command)|TYPE]]
{{div col end}}

====External commands====
{{div col|colwidth=9em}}
* [[Assembly language#Assembler|ASM]]
* [[CHKDSK]]
* [[DEBUG (DOS command)|DEBUG]]
* [[EDLIN]]
* HEX2BIN
* MAKRDCPM
* RDCPM
* [[SYS (DOS command)|SYS]]
* [[TRANS.COM|TRANS]]
{{div col end}}

=====EDLIN=====
By 1982, when IBM asked Microsoft to release a version of DOS that was compatible with a [[hard disk drive]], [[PC&nbsp;DOS 2.0]] was an almost complete rewrite of DOS, so by March 1983, very little of 86-DOS remained. The most enduring element of 86-DOS was its primitive line editor, [[EDLIN]], which remained the only editor supplied with Microsoft versions of DOS until the June 1991 release of [[MS-DOS 5.0]], which included a [[text-based user interface]] editor called [[MS-DOS Editor]], based on [[QBasic]]. EDLIN can still be used on contemporary machines, since there is an emulated DOS environment up to Windows 10 (32 bit).

===Supported disk formats{{Anchor|Formats}}===
Seattle Computer Products' 86-DOS supported the [[File Allocation Table#FAT12|FAT12]] filesystem on a range of 8-inch and 5.25-inch floppy disk drives on [[S-100 bus|S-100]] floppy disk controller hardware manufactured by [[Cromemco]], [[Tarbell Cassette Interface|Tarbell Electronics]] and [[North Star Computers]]. The [[Western Digital FD1771]]-based Cromemco and Tarbell boards supported one-sided, single-density soft-sectored drives. A Tarbell double-density board utilizing the [[Western Digital FD1771|FD1791]] was supported as well. Later, SCP offered advanced floppy disk controllers, like the Disk Master series.

86-DOS<!-- at least up to including 1.00 --> did not take advantage of a [[Design of the FAT file system#FATID|FAT ID]] byte<ref group="nb" name="NB_FATID_FEh" /> or [[BIOS parameter block]] (BPB), as later DOS versions do, to distinguish between different media formats; instead different drive letters were hard-coded at time of compilation to be associated with different physical floppy drives, sides and densities. That meant, depending on its type, a disk had to be addressed under a certain drive letter to be recognized correctly.  This concept was later emulated with more flexibility by [[DRIVER.SYS]] under DOS 3.x and later versions.

Two logical format variants of the 86-DOS 12-bit FAT format existed—the original format with 16-byte directory entries and the later format (since [[86-DOS#0B|86-DOS 0.42]]) with 32-byte directory entries. Only the second one is logically compatible with the FAT12 format known since the release of MS-DOS and PC&nbsp;DOS. MS-DOS still cannot mount such volumes, as in absence of a BPB it falls back to retrieve the FAT ID in the FAT entry for [[Design of the FAT file system#CLUST 0|cluster 0]] to choose among hard-coded disk geometry profiles. In all formats of a volume formatted under MS-DOS that would otherwise be supported by both systems and typically also in all other formats, this ID is located in the first byte of logical sector 1—that is, the volume's second sector with physical [[cylinder-head-sector]] (CHS) address 0/0/2 or [[logical block addressing]] (LBA) address 1—since MS-DOS assumes a single reserved sector, the boot sector. Under 86-DOS, the [[Design of the FAT file system#Bootsector|reserved sectors area]] is significantly larger (whole tracks), and therefore the prototypical<!-- because 86-DOS does not make use of it, at least not in early versions --> FAT ID {{code|0xFE}} (and {{code|0xFF}}) is located elsewhere on disk, making it impossible for MS-DOS to retrieve it, and even if it would, the hard-coded disk profile associated with it would not take this larger reserved sectors region under 86-DOS into account.<ref group="nb" name="NB_FATID_FEh" />

[[CP/M|CP/M&nbsp;2]] floppy media were readable through [[#RDCPM|RDCPM]].

86-DOS did not offer any specific support for [[Hard disk drive|fixed disks]], but third-party solutions in form of hard disk controllers and corresponding I/O system extensions for 86-DOS were available from companies like [[Tallgrass Technologies]], making hard disks accessible similar to [[Floppy disk variants#Superfloppy|superfloppies]] within the size limits of the FAT12 file system.<!-- most probably without any kind of partitioning, but if so, not in the later MBR partitioning scheme as introduced with PC DOS 2.0 -->

{| class="wikitable" style="text-align:right;"
|-
! style="text-align:right;" | Size
| [[Floppy disk#8.0|8&nbsp;inch]] || <!-- 8&nbsp;inch || -->8&nbsp;inch || 8&nbsp;inch || [[Floppy disk#5.25|5.25&nbsp;inch]] || 5.25&nbsp;inch
|-
! style="text-align:right;" | Density
| [[Disk density#SD|SD]] || <!-- SD || -->[[Disk density#DD|DD]] || DD || SD || SD
|-
! style="text-align:right;" | Modulation
| [[Frequency modulation|FM]] || <!-- FM || -->[[Modified Frequency Modulation|MFM]] || MFM || FM || FM
|-
! style="text-align:right;" | Formatted capacity (KB)
| 250.25<ref name="86-DOS_Files" />
| | <!-- 500.5 || -->616<ref name="86-DOS_Files" />
| | 1232<ref name="86-DOS_Files" />
| | 90<ref name="86-DOS_Files" />
| | 87.5<ref name="86-DOS_Files" />
|-
! style="text-align:right;" | Cylinders (CHS)
| 77 || <!-- 77 || -->77 || 77 || 40 || 35
|-
! style="text-align:right;" | Physical sectors / track
| 26 || <!-- 26 || -->8 || 8 || 18 || 10
|-
! style="text-align:right;" | Number of heads
| 1 || <!-- 2 || -->1 || 2 || 1 || 1
|-
! style="text-align:right;" | Byte payload / physical sector
| 128 || <!-- 128 || -->1024 || 1024 || 128 || 256
|-
! style="text-align:right;" | Bytes / logical sector
| 128 || <!-- 128 || -->1024 || 1024 || 128 || 256
|-
! style="text-align:right;" | Logical sectors / cluster
| 4 || <!-- 4 || -->1 || 1 || 2 || 1
|-
! style="text-align:right;" | Reserved logical sectors
| 52 (2 tracks) || <!-- ? || -->1 || 1 || 54 (3 tracks) || 30 (3 tracks)
|-
! style="text-align:right;" | Number of FATs
| 2 || <!-- 2 || -->2 || 2 || 2 || 2
|-
! style="text-align:right;" | Root directory entries<br />(á 32 bytes,<br />86-DOS 0.42 and higher only)
| 64 (16 sectors) || <!-- 64 (16 sectors) || -->96 (3 sectors) || 128 (4 sectors) || 64 (16 sectors) || 64 (8 sectors)
|-
! style="text-align:right;" | Root directory entries<br />(á 16 bytes)
| 64 || <!-- 64 || -->{{dunno}} || {{dunno}} || 64 || {{N/A}}
|-
! style="text-align:right;" | Total logical sectors
| 2002 || <!-- 4004 || -->616 || 1232 || 720 || 350
|-
! style="text-align:right;" | Logical sectors / FAT
| {{dunno|6?}} || <!-- ? || -->{{dunno}} || {{dunno}} || {{dunno}} || {{dunno}}
|-
! style="text-align:right;" | Hidden sectors
| 0 || <!-- 0 || -->0 || 0 || 0 || 0
|-
! style="text-align:right;" | Logical sector order
| {{dunno}} || <!-- ? || -->{{dunno}} || {{dunno}} || {{dunno}} || {{dunno}}
|-
<!-- | Sector interleave || {{dunno}} || {{dunno}} || {{dunno}} || {{dunno}} || {{dunno}} || {{dunno}} -->
<!-- | Head skew || {{N/A}} || {{dunno}} || {{N/A}} || {{dunno}} || {{N/A}} || {{N/A}} -->
! style="text-align:right;" | Sector mapping
| sector+/ track+ || <!-- sector+/ head+/ track+? --><!-- or sector+/ track+/ head+? --><!-- || -->sector+/ track+ || sector+/ head+/ track+ || sector+/ track+ || sector+/ track+
|-
! style="text-align:right;" | First physical sector
| 1 || <!-- 1 || --> 1 || 1 || 1 || 0
|-
! style="text-align:right;" | Sector index
| [[Floppy disk|Soft]] || <!-- Soft || --> Soft || Soft || Soft || [[Hard sectoring|Hard]] (10+1)
|-
! style="text-align:right;" | Controller type
| Cromemco/Tarbell [[Western Digital FD1771|FD1771]] || <!-- ? --><!-- not sure if the 500.5 KB format is actually supported by 86-DOS. If so, only by Tarbell --><!-- || -->[[Tarbell Cassette Interface|Tarbell]] [[Western Digital FD1771|FD1791]] || Tarbell FD1791 || [[Cromemco]] FD1771 || [[North Star Computers|NorthStar]]<!-- with Shugart SA-400 drives -->
|-
! style="text-align:right;" | [[Design of the FAT file system#FATID|FAT ID]]
| {{No}} (FEh)<ref group="nb" name="NB_FATID_FEh" /> || <!-- No || -->{{No}} (FEh)<ref group="nb" name="NB_FATID_ELSE" /> || {{No}} (FEh)<ref group="nb" name="NB_FATID_ELSE" /> || {{No}} (FEh)<ref group="nb" name="NB_FATID_ELSE" /> || {{No}} (FEh)<ref group="nb" name="NB_FATID_ELSE" />
|-
! style="text-align:right;" | [[BIOS parameter block|BPB]] presence
| {{No}} || <!-- No || -->{{No}} || {{No}} || {{No}} || {{No}}
|}

Various OEM versions of MS-DOS 1.2x and 2.x supported a number of similar 8-inch FAT12 floppy disk formats as well, although not identical to those supported by 86-DOS.<ref group="nb" name="NB_FATID_FEh" />

Disk formats supported by one of the last versions<!-- 1.25 or 1.26 --> developed by Tim Paterson at Microsoft, [[SCP MS-DOS 1.25|MS-DOS 1.25]]<!-- circular link --> <ref name="Paterson_2014_MSDOS125" /><ref name="SCP_MS-DOS_1.25_Files" /><ref name="Shustek_2014_MS-DOS" /><ref name="Levin_2014_MS-DOS" /> (March 1982) for the ''SCP Gazelle'' computer with SCP controller or Cromemco 16FDC controller (by default, this version only supported the MS-DOS-compatible variants of the 8.0&nbsp;in formats with a single reserved sector but it could be built to provide two extra drive letters to read and write floppies in the previous SCP 86-DOS 8.0&nbsp;in disk formats since 0.42 as well):

{| class="wikitable" style="text-align:right;"
|-
! style="text-align:right;" | Size
| [[Floppy disk#8.0|8&nbsp;inch]] || 8&nbsp;inch || <!-- 8&nbsp;inch || -->8&nbsp;inch || 8&nbsp;inch || 8&nbsp;inch || [[Floppy disk#5.25|5.25]]&nbsp;inch || 5.25&nbsp;inch || 5.25&nbsp;inch
|-
! style="text-align:right;" | Density
| [[Disk density#SD|SD]] || SD || <!-- SD || -->[[Disk density#DD|DD]] || DD || DD || SD || DD || DD
|-
! style="text-align:right;" | Modulation
| [[Frequency modulation|FM]] || FM || <!-- FM || -->[[Modified Frequency Modulation|MFM]] || MFM || MFM || FM || MFM || MFM
|-
! style="text-align:right;" | Formatted capacity (KB)
| style="background:#F2F2F2;" | 250.25 (SCP) || 250.25 (MS) || <!-- 500.5 || -->616 || style="background:#F2F2F2;" | 1232 (SCP) || 1232 (MS) || 90 || 160 || 320
|-
! style="text-align:right;" | Cylinders (CHS)
| 77 || 77 || <!-- 77 || -->77 || 77 || 77 || 40 || 40 || 40
|-
! style="text-align:right;" | Physical sectors / track<ref group="nb" name="NB_BPB_0Dh" />
| 26 || 26 || <!-- 26 || -->8 || 8 || 8 || 18 || 8 || 8
|-
! style="text-align:right;" | Number of heads<ref group="nb" name="NB_BPB_0Fh" />
| 1 || 1 || <!-- 2 || -->1 || 2 || 2 || 1 || 1 || 2
|-
! style="text-align:right;" | Byte payload / physical sector
| 128 || 128 || <!-- 128 || -->1024 || 1024 || 1024 || 128 || 512 || 512
|-
! style="text-align:right;" | Bytes / logical sector<ref group="nb" name="NB_BPB_00h" />
| 128 || 128 || <!-- 128 || -->1024 || 1024 || 1024 || 128 || 512 || 512
|-
! style="text-align:right;" | Logical sectors / cluster<ref group="nb" name="NB_BPB_02h" />
| 4 || 4 || <!-- 4 || -->1 || 1 || 1 || 2 || 1 || 2
|-
! style="text-align:right;" | Reserved logical sectors<ref group="nb" name="NB_BPB_03h" />
| style="background:#F2F2F2;" | 52 (2 tracks) || 1 || <!-- ? || -->1 || 1 || 1 || 54 (3 tracks) || 1 || 1
|-
! style="text-align:right;" | Number of FATs<ref group="nb" name="NB_BPB_05h" />
| 2 || 2 || <!-- 2 || -->2 || 2 || 2 || 2 || 2 || 2
|-
! style="text-align:right;" | Root directory entries<br />(á 32 bytes)<ref group="nb" name="NB_BPB_06h" />
| style="background:#F2F2F2;" | 64 (16 sectors) || 68 (17 sectors) || <!-- 64? (16? sectors) || -->96 (3 sectors) || style="background:#F2F2F2;" | 128 (4 sectors) || 192 (6 sectors) || 64 (16 sectors) || 64 (4 sectors) || 112 (7 sectors)
|-
! style="text-align:right;" | Total logical sectors<ref group="nb" name="NB_BPB_08h" />
| 2002 || 2002 || <!-- 4004 || -->616 || 1232 || 1232 || 720 || 320 || 640
|-
! style="text-align:right;" | Logical sectors / FAT<ref group="nb" name="NB_BPB_0Bh" />
| {{dunno|style=background:#F2F2F2;|6?}} || 6 || <!-- ? || -->1 || {{dunno|style=background:#F2F2F2;}} || 2 || 4 || 1 || 1
|-
! style="text-align:right;" | Hidden sectors<ref group="nb" name="NB_BPB_11h" />
| 0 || 0<ref group="nb" name="NB_Microsoft_Hidden" /> || <!-- 0 || -->0 || 0 || 0 || 0 || 0 || 0
|-
! style="text-align:right;" | Total number of clusters<!-- unless there were bad sectors -->
| {{dunno}} || 497 || <!-- ? || -->{{dunno}} || {{dunno}} || 1227 || {{dunno}} || 313 || 315
|-
! style="text-align:right;" | Logical sector order
| {{dunno}} || {{dunno}} || <!-- ? || -->{{dunno}} || {{dunno}} || {{dunno}} || {{dunno}} || {{dunno}} || {{dunno}}
|-
<!-- | Sector interleave || {{dunno}} || {{dunno}} || {{dunno}} || {{dunno}} || {{dunno}} || {{dunno}} || {{dunno}} || {{dunno}} -->
<!-- | Head skew || {{N/A}} || {{N/A}} || {{dunno}} || {{N/A}} || {{N/A}} || {{dunno}} || {{N/A}} || {{N/A}} || {{dunno}} -->
! style="text-align:right;" | Sector mapping
| sector+/ track+ || sector+/ track+ || <!-- sector+/ head+/ track+? --><!-- or sector+/ track+/ head+? --><!-- || -->sector+/ track+ || sector+/ head+/ track+ || sector+/ head+/ track+ || sector+/ track+ || sector+/ track+ || sector+/ head+/ track+
|-
! style="text-align:right;" | First physical sector
| 1 || 1 || <!-- 1 || --> 1 || 1 || 1 || 1 || 1 || 1
|-
! style="text-align:right;" | Sector index
| [[Floppy disk|Soft]] || Soft || <!-- Soft || --> Soft || Soft || Soft || Soft || Soft || Soft
|-
! style="text-align:right;" | Controller type
| Cromemco&nbsp;/ Tarbell [[Western Digital FD1771|FD1771]] || Cromemco&nbsp;/ Tarbell FD1771 || <!-- ? --><!-- not sure if the 500.5 KB format is actually supported by 86-DOS. If so, only by Tarbell --><!-- || -->[[Tarbell Cassette Interface|Tarbell]] [[Western Digital FD1771|FD1791]]&nbsp;/ [[Western Digital FD1771|FD1793]] || Tarbell FD1791&nbsp;/ FD1793 || Tarbell FD1791&nbsp;/ FD1793 || [[Cromemco]] 4FDC FD1771 || SCP / Cromemco 16FDC || SCP / Cromemco 16FDC
|-
! style="text-align:right;" | [[Design of the FAT file system#FATID|FAT ID]]<ref group="nb" name="NB_FATID_FEh" /><ref group="nb" name="NB_BPB_0Ah" />
| FEh || FEh || <!-- || -->FEh || FEh || FEh || FEh || FEh || FFh
|-
! style="text-align:right;" | [[BIOS parameter block|BPB]] Presence
| {{No}} || {{No}} || <!-- No || -->{{No}} || {{No}} || {{No}} || {{No}} || {{No}} || {{No}}
|}
In 1984 Seattle Computer Products released an OEM version of [[SCP MS-DOS 2.0|MS-DOS 2.0]]<!-- circular link --> for the SCP S-100 computer with SCP-500 Disk Master Floppy controller. It added support for 5.25&nbsp;in DD/1S (180&nbsp;KB) and DD/2S (360&nbsp;KB) FAT12 formats and supported the older formats as well<!-- at least 8.0 in DD/1S on Qume QumeTrak 842 and 5.25 in DD/2S on TEAC FD-55B-01-U. -->, although possibly with some of the parameters<!-- TDB: reserved sectors, FAT ID, BPB --> modified compared to [[MS-DOS 1.25]].<ref name="Bob_2009" />