86-DOS (known internally as QDOS,
for Quick and Dirty Operating System) is a discontinued
operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs.
Time-sharing operating systems schedule tasks for efficient use of the system and may also i ...
developed and marketed by
Seattle Computer Products (SCP) for its
Intel 8086-based computer kit.
86-DOS shared a few of its commands with other operating systems like
OS/8
OS/8 is the primary operating system used on the Digital Equipment Corporation's PDP-8 minicomputer.
PDP-8 operating systems which precede OS/8 include:
* R-L Monitor, also referred to as MS/8.
* P?S/8, requiring only 4K of memory.
* PDP-8 4K ...
and
CP/M, which made it easy to
port
A port is a maritime facility comprising one or more wharves or loading areas, where ships load and discharge cargo and passengers. Although usually situated on a sea coast or estuary, ports can also be found far inland, such as H ...
programs from the latter. Its
application programming interface was very similar to that of CP/M. The system was licensed and then purchased by
Microsoft
Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washin ...
and developed further as
MS-DOS
MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few ope ...
and
PC DOS.
History
Origins
86-DOS was created because sales of the
Seattle Computer Products 8086
computer kit, demonstrated in June 1979 and shipped in November,
were languishing due to the absence of an operating system. The only software that SCP could sell with the board was Microsoft's
Standalone Disk BASIC-86, which Microsoft had developed on a prototype of SCP's hardware.
SCP wanted to offer the 8086-version of
CP/M that Digital Research had initially announced for November 1979, but it was delayed and its release date was uncertain. This was not the first time Digital Research had lagged behind hardware developments; two years earlier it had been slow to adapt CP/M for new
floppy disk formats and
hard disk drive
A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating platters coated with magne ...
s. In April 1980, SCP assigned 24-year-old
Tim Paterson
Tim Paterson (born 1 June 1956) is an American computer programmer, best known for creating 86-DOS, an operating system for the Intel 8086. This system emulated the application programming interface (API) of CP/M, which was created by Gary ...
to develop a substitute for
CP/M-86.
Using a CP/M-80 manual as reference
Paterson modeled 86-DOS after its architecture and interfaces, but adapted to meet the requirements of Intel's 8086
16-bit
16-bit microcomputers are microcomputers that use 16-bit microprocessors.
A 16-bit register can store 216 different values. The range of integer values that can be stored in 16 bits depends on the integer representation used. With the two mo ...
processor, for easy (and partially automated) source-level translatability of the many existing
8-bit CP/M programs;
porting them to either DOS or CP/M-86 was about equally difficult,
and eased by the fact that Intel had already published a method that could be used to automatically translate software from the
Intel 8080
The Intel 8080 (''"eighty-eighty"'') is the second 8-bit microprocessor designed and manufactured by Intel. It first appeared in April 1974 and is an extended and enhanced variant of the earlier 8008 design, although without binary compatibil ...
processor, for which CP/M had been designed, to the new 8086 instruction set. At the same time he made a number of changes and enhancements to address what he saw as CP/M's shortcomings. CP/M
cached file system information in memory for speed, but this required a user to force an update to a disk before removing it; if the user forgot, the disk would become corrupt. Paterson took the safer, but slower approach of updating the disk with each operation. CP/M's
PIP command, which copied files, supported several special file names that referred to hardware devices such as
printer
Printer may refer to:
Technology
* Printer (publishing), a person or a company
* Printer (computing), a hardware device
* Optical printer for motion picture films
People
* Nariman Printer (fl. c. 1940), Indian journalist and activist
* James ...
s and
communication ports. Paterson built these names into the operating system as
device file
In Unix-like operating systems, a device file or special file is an interface to a device driver that appears in a file system as if it were an ordinary file. There are also special files in DOS, OS/2, and Windows. These special files allow a ...
s so that any program could use them. He gave his copying program the more intuitive name
COPY
Copy may refer to:
*Copying or the product of copying (including the plural "copies"); the duplication of information or an artifact
**Cut, copy and paste, a method of reproducing text or other data in computing
**File copying
**Photocopying, a pr ...
. Rather than implementing CP/M's
file system, he drew on Microsoft Standalone Disk BASIC-86's
File Allocation Table (FAT) file system.
By mid-1980 SCP advertised 86-DOS, priced at for owners of its 8086-board and for others. It touted the software's ability to read
Zilog Z80
The Z80 is an 8-bit microprocessor introduced by Zilog as the startup company's first product. The Z80 was conceived by Federico Faggin in late 1974 and developed by him and his 11 employees starting in early 1975. The first working samples were ...
source code from a CP/M disk and translate it to 8086 source code, and promised that only "minor hand correction and optimization" was needed to produce 8086 binaries.
IBM interest
In October 1980,
IBM was developing what would become the original
IBM Personal Computer
The IBM Personal Computer (model 5150, commonly known as the IBM PC) is the first microcomputer released in the IBM PC model line and the basis for the IBM PC compatible de facto standard. Released on August 12, 1981, it was created by a team ...
. CP/M was by far the most popular operating system in use at the time, and IBM felt it needed CP/M in order to compete. IBM's representatives visited Digital Research and discussed
licensing
A license (or licence) is an official permission or permit to do, use, or own something (as well as the document of that permission or permit).
A license is granted by a party (licensor) to another party (licensee) as an element of an agreeme ...
with Digital Research's licensing representative,
Dorothy Kildall (née McEwen), who hesitated to sign IBM's
non-disclosure agreement. Although the NDA was later accepted, Digital Research would not accept IBM's proposal of in exchange for as many copies as IBM could sell, insisting on the usual
royalty
Royalty may refer to:
* Any individual monarch, such as a king, queen, emperor, empress, etc.
* Royal family, the immediate family of a king or queen regnant, and sometimes his or her extended family
* Royalty payment for use of such things as int ...
-based plan.
In later discussions between IBM and
Bill Gates
William Henry Gates III (born October 28, 1955) is an American business magnate and philanthropist. He is a co-founder of Microsoft, along with his late childhood friend Paul Allen. During his career at Microsoft, Gates held the positions ...
, Gates mentioned the existence of 86-DOS and IBM representative Jack Sams told him to get a license for it.
Creation of PC DOS
Microsoft purchased a non-exclusive license for 86-DOS from Seattle Computer Products
in December 1980 for . In May 1981, it hired Tim Paterson to port the system to the IBM PC,
which used the slower and less expensive
Intel 8088
The Intel 8088 ("''eighty-eighty-eight''", also called iAPX 88) microprocessor is a variant of the Intel 8086. Introduced on June 1, 1979, the 8088 has an eight-bit external data bus instead of the 16-bit bus of the 8086. The 16-bit registers and ...
processor and had its own specific family of peripherals. IBM watched the developments daily,
submitting over 300
change requests before it accepted the product and wrote the user manual for it.
In July 1981, a month before the PC's release, Microsoft purchased all rights to 86-DOS from SCP for .
It met IBM's main criteria: it looked like CP/M,
and it was easy to adapt existing 8-bit CP/M programs to run under it, notably thanks to the
TRANS
Trans- is a Latin prefix meaning "across", "beyond", or "on the other side of".
Used alone, trans may refer to:
Arts, entertainment, and media
* Trans (festival), a former festival in Belfast, Northern Ireland, United Kingdom
* ''Trans'' (fil ...
command which would translate source files from 8080 to 8086 machine instructions. Microsoft licensed 86-DOS to IBM, and it became PC DOS 1.0. This license also permitted Microsoft to sell DOS to other companies, which it did. The deal was spectacularly successful, and SCP later claimed in court that Microsoft had concealed its relationship with IBM in order to purchase the operating system cheaply. SCP ultimately received a million settlement payment.
Intellectual property dispute
When Digital Research founder
Gary Kildall
Gary Arlen Kildall (; May 19, 1942 – July 11, 1994) was an American computer scientist and microcomputer entrepreneur.
During the 1970s, Kildall created the CP/M operating system among other operating systems and programming tools, an ...
examined PC DOS and found that it duplicated CP/M's programming interface, he wanted to sue IBM, which at the time claimed that PC DOS was its own product. However, Digital Research's attorney did not believe that the relevant law was clear enough to sue. Nonetheless, Kildall confronted IBM and persuaded them to offer CP/M-86 with the PC in exchange for a release of liability.
Controversy has continued to surround the similarity between the two systems. Perhaps the most sensational claim came from
Jerry Pournelle
Jerry Eugene Pournelle (; August 7, 1933 – September 8, 2017) was an American scientist in the area of operations research and human factors research, a science fiction writer, essayist, journalist, and one of the first bloggers. In the 1960s ...
, who said that Kildall personally demonstrated to him that DOS contained CP/M code by entering a command in DOS that displayed Kildall's name,
but Pournelle never revealed the command and nobody has come forward to corroborate his story. A 2004 book about Kildall says that he used such an encrypted message to demonstrate that other manufacturers had copied CP/M, but does not say that he found the message in DOS;
instead Kildall's memoir (a source for the book) pointed to the well-known interface similarity. Paterson insists that the 86-DOS software was his original work, and has denied referring to or otherwise using CP/M code while writing it.
After the 2004 book appeared, he sued the authors and publishers for
defamation.
The court ruled in
summary judgment
In law, a summary judgment (also judgment as a matter of law or summary disposition) is a judgment entered by a court for one party and against another party summarily, i.e., without a full trial. Summary judgments may be issued on the merits of ...
that no defamation had occurred, as the book's claims were opinions based on research, or were not provably false.
Versions
Features
Commands
The following list of
commands is supported by 86-DOS.
Internal commands
* CLEAR
*
COPY
Copy may refer to:
*Copying or the product of copying (including the plural "copies"); the duplication of information or an artifact
**Cut, copy and paste, a method of reproducing text or other data in computing
**File copying
**Photocopying, a pr ...
*
DIR
*
ERASE
Erase may refer to:
*Data erasure, a method of software-based overwriting that completely destroys all electronic data
*Data remanence, the residual representation of data that has been, in some way, nominally erased or removed
* ''Erase'' (album ...
*
RENAME
*
TYPE
External commands
*
ASM
*
CHKDSK
In computing, CHKDSK (short for "check disk") is a system tool and command in DOS, Digital Research FlexOS, IBM/Toshiba 4690 OS, IBM OS/2, Microsoft Windows and related operating systems. It verifies the file system integrity of a volume and ...
*
DEBUG
*
EDLIN
* HEX2BIN
* MAKRDCPM
* RDCPM
*
SYS
*
TRANS
Trans- is a Latin prefix meaning "across", "beyond", or "on the other side of".
Used alone, trans may refer to:
Arts, entertainment, and media
* Trans (festival), a former festival in Belfast, Northern Ireland, United Kingdom
* ''Trans'' (fil ...
=EDLIN
=
By 1982, when IBM asked Microsoft to release a version of DOS that was compatible with a
hard disk drive
A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating platters coated with magne ...
,
PC 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
In computing, text-based user interfaces (TUI) (alternately terminal user interfaces, to reflect a dependence upon the properties of computer terminals and not just text), is a retronym describing a type of user interface (UI) common as an ear ...
editor called
MS-DOS Editor
__NOTOC__
MS-DOS Editor, commonly just called ''edit'' or ''edit.com'', is a TUI text editor that comes with MS-DOS 5.0 and later, as well as all "x86" SKUs of Windows, until Windows 11. It supersedes edlin, the standard editor in earlier versi ...
, based on
QBasic
QBasic is an integrated development environment (IDE) and interpreter for a variety of dialects of BASIC which are based on QuickBASIC. Code entered into the IDE is compiled to an intermediate representation (IR), and this IR is immediately e ...
. EDLIN can still be used on contemporary machines, since there is an emulated DOS environment up to Windows 10 (32 bit).
Supported disk formats
Seattle Computer Products' 86-DOS supported the
FAT12
File Allocation Table (FAT) is a file system developed for personal computers. Originally developed in 1977 for use on floppy disks, it was adapted for use on hard disks and other devices. It is often supported for compatibility reasons by ...
filesystem on a range of 8-inch and 5.25-inch floppy disk drives on
S-100 floppy disk controller hardware manufactured by
Cromemco
Cromemco was a Mountain View, California microcomputer company known for its high-end Z80-based S-100 bus computers and peripherals in the early days of the personal computer revolution.
The company began as a partnership in 1974 between Harry ...
,
Tarbell Electronics and
North Star Computers
North Star Computers Inc. (later styled as NorthStar) was an American computer company based in Berkeley, California existing between June 1976 (when according to popular rumor it was formed as "Kentucky Fried Computers") and 1989. Originally a mai ...
. The
Western Digital FD1771
The FD1771, sometimes WD1771, is the first in a line of floppy disk controllers produced by Western Digital. It uses single density FM encoding introduced in the IBM 3740. It is packaged in a 40-pin DIP."The FD1771 is a single-chip floppy disk ...
-based Cromemco and Tarbell boards supported one-sided, single-density soft-sectored drives. A Tarbell double-density board utilizing the
FD1791 was supported as well. Later, SCP offered advanced floppy disk controllers, like the Disk Master series.
86-DOS did not take advantage of a
FAT ID
A FAT file system is a specific type of computer file system architecture and a family of industry-standard file systems utilizing it.
The FAT file system is a legacy file system which is simple and robust. It offers good performance even in ...
byte
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 0.42
86-DOS (known internally as QDOS, for Quick and Dirty Operating System) is a discontinued operating system developed and marketed by Seattle Computer Products (SCP) for its Intel 8086-based computer kit.
86-DOS shared a few of its commands w ...
) 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 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
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
Cylinder-head-sector (CHS) is an early method for giving addresses to each physical block of data on a hard disk drive.
It is a 3D-coordinate system made out of a vertical coordinate ''head'', a horizontal (or radial) coordinate ''cylinder'', a ...
(CHS) address 0/0/2 or
logical block addressing
Logical block addressing (LBA) is a common scheme used for specifying the location of blocks of data stored on computer storage devices, generally secondary storage systems such as hard disk drives. LBA is a particularly simple linear address ...
(LBA) address 1—since MS-DOS assumes a single reserved sector, the boot sector. Under 86-DOS, the
reserved sectors area is significantly larger (whole tracks), and therefore the prototypical FAT ID (and ) 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.
CP/M 2
CP/M, originally standing for Control Program/Monitor and later Control Program for Microcomputers, is a mass-market operating system created in 1974 for Intel 8080/ 85-based microcomputers by Gary Kildall of Digital Research, Inc. Initial ...
floppy media were readable through
RDCPM.
86-DOS did not offer any specific support for
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
superfloppies within the size limits of the FAT12 file system.
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.
Disk formats supported by one of the last versions developed by Tim Paterson at Microsoft,
MS-DOS 1.25 (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 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 in disk formats since 0.42 as well):
In 1984 Seattle Computer Products released an OEM version of
MS-DOS 2.0
MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few ope ...
for the SCP S-100 computer with SCP-500 Disk Master Floppy controller. It added support for 5.25 in DD/1S (180 KB) and DD/2S (360 KB) FAT12 formats and supported the older formats as well, although possibly with some of the parameters modified compared to
MS-DOS 1.25.
See also
*
MIDAS
Midas (; grc-gre, Μίδας) was the name of a king in Phrygia with whom several myths became associated, as well as two later members of the Phrygian royal house.
The most famous King Midas is popularly remembered in Greek mythology for his ...
*
MSX-DOS
MSX-DOS is a discontinued disk operating system developed by Microsoft for the 8-bit home computer standard MSX, and is a cross between MS-DOS 1.25 and CP/M-80 2.
MSX-DOS
MSX-DOS and the extended BASIC with 3½-inch floppy disk supp ...
Notes
References
Further reading
* (41 pages)
External links
86-DOS documentationfrom Paterson Technology
in the Altair 8800 SIMH simulator by Howard M. Harte
{{DEFAULTSORT:86-Dos
Microcomputer software
Disk operating systems
DOS variants
Floppy disk-based operating systems
Discontinued operating systems
Proprietary operating systems
1979 software
Assembly language software