Heath Disk Operating System - HDOS

Heath Company started with their own operating system call HDOS. See Wikipedia for more info on HDOS.

Here is an interesting article, by Kirk L. Thompson, about the history HDOS, including information about Heath Company releasing HDOS into the public domain.

Known Versions:


    Issue Number




    This first release of HDOS from Heath Company only supported the Heathkit H8 and WH17 floppy drive system (with a max of 2 drives). This version will not boot on an H89 since the console interfaced was handled with a 8251 serial chip, which was not available on the H89. HDOS was written by J. Gordon Letwin and released in 1978.



    This version of 1.0 added support for the 8250 serial chip used as the console port on the H-89. It was released in 1979. Gregg Chandler was responsible for this release.



    This version still only supported the WH17 (with a max of 2 drives) and was released in 1979. Gregg Chandler was responsible for this release.



    This version increased the number of supported 5.25" floppy drives to three. It was released in 1980.  Gregg Chandler was responsible for this release. 



    This version added support for the 8" Floppy drive (H/Z-47 - Z-89-47). It was released in 1980. Gregg Chandler was responsible for this release. It was released into the public domain in April 1988.



    This was a small update that added support for the soft-sectored controller (H/Z-37 - Z-89-37).



    This version, added support for the ORG-0 modification which allowed HDOS to use the full 64K RAM, just as CP/M. Previous releases, supported a maximum of 56K RAM since system ROM/RAM occupied the lower 8K. Gregg Chandler worked on this version, but it was not completed due to higher priority work on the H/Z100. It was released into the public domain in August 1986.

    Information from the Summer 1978 Heathkit catalog:

    The H8-17 is the operating system software for the H8/H17 system.
    This software includes the Heath Disk operating system (HDOS), with its unique diagnostic for unit evaluation and optimization; the BUG-8 console debugger; TED-8, our powerful text editor; HASL-8 assembly language; and extended Benton Harbor BASIC. With extra diskette.

    H8-17, Shipping weight. 2 pounds. ............................................Introductory Price $100.00


    Information from the Fall 1978 Heathkit catalog:

    Here's the complete Operating Systems Software for the WH17 Floppy Disk System

    The Operating Systems Software for the WH17 Floppy Disk System includes a diskette containing the standard H8 software plus a unique diagnostic for optimum system setup and evaluation. This software includes extended Benton Harbor BASIC with strings and files; a 2-pass absolute assembler that generates efficient machine language codes; a text editor to prepare source code for BASIC and other languages; a console debugger for easy debugging of user machine language programs via an external terminal; and a full set of disk utility programs for convenient file manipulation. Special features of this operating software include Dynamic File Allocation which automatically keeps free space available to permit unlimited file size and prevent squeezing of disks. It also prevents estimating or predeclaring file size before writing to provide more efficient use of file space. Special facilities support running and backup of single-drive configurations to permit copying and transferring between disks even with a single-drive system. Device independence permits direct communication between any program and any device for added flexibility. A file utility program allows two kinds of wild cards for fast, easy bulk manipulation of files. The software is supplied on a standard diskette. With comprehensive operations and instruction manual.

    H8-17, Shipping weight. 12 pounds...................................................................  $100.00

    Information from the Spring/Summer 1982 Heath catalog discussing version 2.0:

    HDOS has many function of larger systems

    • Sophisticated system controls your H-8 or H/Z-89
    • Designed for efficient use of memory and disk space

    Provides complete operating environment: The Heath Disk Operating System, Ver. 2.0, allows program writing, editing and storage - with assembly and checkout facilities. Features Extended Benton Harbor BASIC (Ver. 6.0) and ASM 8080 Assembly Language. 17 versatile commands list content, manipulate disks and files; run programs, select device driver options, display status reports and more. Facilities test disk drives and media; initialize disks and generate system images onto disk; allow you to debug programs and edit text. Supports all disk systems except Z-67. HDOS requires an H-8/H-19 or H/Z-89 computer system with a minimum of 48K bytes of RAM and one disk drive. Two drives are highly recommended, and may be required to use some other software with HDOS.

    HOS-817-1, on hard-sectored 5.25" disk, Shipping weight. 9 pounds ............. $150.00

    HOS-847-1, on soft-sectored 8" disk, Shipping weight. 5 pounds. .................. $150.00

    Last Modified: Wednesday, 16-May-2018 22:48:17 PDT

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    This site is dedicated to preserving the history of the original Heathkit computers. They were initially release in 1977 and included the 8-bit H-8 and 16-bit H-11 systems. The H89 was released in 1979.