HDOS
Encyclopedia
HDOS is an early microcomputer
operating system
, originally written for the Heathkit H8
computer system and later also available for the Heath H89 and Zenith Z-89 computers. The author was Heath Company
employee Gordon Letwin
, who later was an early employee of Microsoft
and lead architect of OS/2
.
HDOS originally came with a limited set of system software tools, including an assembler
, but many commercial and large set of freeware programs from HUG - Heath User Group eventually became available for it.
HDOS 2.0 is notable because it was one of the first microcomputer operating systems to use loadable device driver
s to achieve a degree of device independence and extensibility. Device names followed the RSX-11
-style convention of DKn: where the first two letters were the device driver file name and n was a number (DK0:, DK1:, and so on would all be handled by DK.SYS). Other similarities to RSX included the use of PIP
for file transfer, and the use of EOT
for file termination.
The full source paper listing is held at yesterpc.org, old computer museum. Item references (Heathkit part number) are : HOS-1-SL part number : 595-2466
Microcomputer
A microcomputer is a computer with a microprocessor as its central processing unit. They are physically small compared to mainframe and minicomputers...
operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
, originally written for the Heathkit H8
Heathkit H8
Heathkit's H8 was an Intel 8080-based microcomputer sold in kit form starting in 1977. The H8 was similar to the S-100 bus computers of the era, and like those machines was often used with the CP/M operating system on floppy disk...
computer system and later also available for the Heath H89 and Zenith Z-89 computers. The author was Heath Company
Heathkit
Heathkits were products of the Heath Company, Benton Harbor, Michigan. Their products included electronic test equipment, high fidelity home audio equipment, television receivers, amateur radio equipment, electronic ignition conversion modules for early model cars with point style ignitions, and...
employee Gordon Letwin
Gordon Letwin
James Gordon Letwin is an American software developer and one of the original twelve Microsoft employees.Prior to joining Microsoft, he worked for Heathkit, on HDOS and Benton Harbor Basic....
, who later was an early employee of Microsoft
Microsoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...
and lead architect of OS/2
OS/2
OS/2 is a computer operating system, initially created by Microsoft and IBM, then later developed by IBM exclusively. The name stands for "Operating System/2," because it was introduced as part of the same generation change release as IBM's "Personal System/2 " line of second-generation personal...
.
HDOS originally came with a limited set of system software tools, including an assembler
Assembly language
An assembly language is a low-level programming language for computers, microprocessors, microcontrollers, and other programmable devices. It implements a symbolic representation of the machine codes and other constants needed to program a given CPU architecture...
, but many commercial and large set of freeware programs from HUG - Heath User Group eventually became available for it.
HDOS 2.0 is notable because it was one of the first microcomputer operating systems to use loadable device driver
Device driver
In computing, a device driver or software driver is a computer program allowing higher-level computer programs to interact with a hardware device....
s to achieve a degree of device independence and extensibility. Device names followed the RSX-11
RSX-11
RSX-11 is a family of real-time operating systems mainly for PDP-11 computers created by Digital Equipment Corporation , common in the late 1970s and early 1980s. RSX-11D first appeared on the PDP-11/40 in 1972...
-style convention of DKn: where the first two letters were the device driver file name and n was a number (DK0:, DK1:, and so on would all be handled by DK.SYS). Other similarities to RSX included the use of PIP
Peripheral Interchange Program
Peripheral Interchange Program was a utility to transfer files on and between devices on Digital Equipment Corporation's computers. It was first implemented on the PDP-6 architecture by Harrison "Dit" Morse early in the 1960s...
for file transfer, and the use of EOT
End-of-transmission character
In telecommunication, an end-of-transmission character is a transmission control character. Its intended use is to indicate the conclusion of a transmission that may have included one or more texts and any associated message headings....
for file termination.
The full source paper listing is held at yesterpc.org, old computer museum. Item references (Heathkit part number) are : HOS-1-SL part number : 595-2466
Versions
- HDOS 1.0 – written in 1978 by J. Gordon Letwin
- HDOS 2.0 – released in 1980, written by Gregg Chandler, released into the public domain in April 1988
- HDOS 3.0 – released into the public domain in August 1986
- HDOS 3.02 – enhanced version by Richard Musgrave
See also
- HeathkitHeathkitHeathkits were products of the Heath Company, Benton Harbor, Michigan. Their products included electronic test equipment, high fidelity home audio equipment, television receivers, amateur radio equipment, electronic ignition conversion modules for early model cars with point style ignitions, and...
- Zenith Data SystemsZenith Data SystemsZenith Data Systems was a division of Zenith founded in 1979 after Zenith acquired Heathkit, which had, in 1977, entered the personal computer market. Headquartered in Benton Harbor, Michigan, Zenith sold personal computers under both the Heath/Zenith and Zenith Data Systems names...
- List of operating systems
External links
- HeathDOS
- Michael A. Pechuria, Comparing Two Microcomputer Operating Systems: CP/M and HDOS. Communications of the ACM, March 1983, vol. 26, no. 3.
- www.yesterpc.org The computer museum with large Heathkit computer collection, where full paper listing of HDOS is available
- Society of Eight-Bit Heathkit Computerists A web site dedicated to preserving the Heathkit 8 bit computers, source listing in .pdf form