Disk Image Utility and HDOS
Darrell Pelan
The Heath Disk Operating System Directory Structure, David G Pelowitz, REMark Issue 45
HDOS 3.02 Reference Manual, Jack Rubin, May, 2003
SIDES DENSITY TPI TRACKS SPT GROUPS SPG Sectors Size
glenn.f...@gmail.com
Tom Jorgenson’s “dissecting” article from Microcomputing is also good
https://sebhc.github.io/sebhc/documentation/supplemental/HDOS_Disk.pdf
or see references in my “squeezing space” article in REMark for some other possibly related topics:
http://pestingers.net/pdfs/remark-scans/1984/remark-volume5-issue2-1984.pdf
(p. 62)
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pel...@gmail.com
Excellent! Thanks for additional references.
Darrell
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Darrell Pelan
The Heath Disk Operating System (HDOS) was a disk operating system used by the Heathkit H8 and H89 computers in the 1970s and 1980s. The HDOS disk format was designed to store and retrieve data on floppy disks, and it used a specific structure to organize data on the disk.
The HDOS disk format used a 5.25-inch floppy disk, which could hold up to 360 kilobytes of data. The disk was divided into 80 tracks, with each track containing 18 sectors. Each sector could hold 256 bytes of data, for a total of 4,608 bytes per track.
The first two tracks of the HDOS disk were reserved for system information, including the boot sector and directory information. The boot sector contained the code that would be loaded when the computer started up, while the directory information contained a list of files and their locations on the disk.
The remaining 78 tracks of the disk were available for storing data files. Each file was stored as a contiguous block of sectors, with a maximum file size of 65,280 bytes. Files could be organized into subdirectories, with each directory holding up to 64 files.
To access data on an HDOS disk, the computer would first read the boot sector to load the operating system into memory. The directory information could then be accessed to locate specific files on the disk.
Overall, the HDOS disk format was a relatively simple and efficient way to store and retrieve data on floppy disks, and it played an important role in the development of early personal computers.
To boot an H8 or H89 computer using the Heath Disk Operating System (HDOS), there are certain files that must be present on the disk:
BOOT - This is the bootstrap loader program that is loaded by the computer when it is started up. The BOOT program is responsible for initializing the system and loading the HDOS operating system into memory.
HDOS.SYS - This is the main HDOS operating system file. It contains the core operating system code that controls the computer's hardware and manages the file system.
HDOSDIR.SYS - This is the directory file that contains information about the files and directories on the disk. It is used by the operating system to locate files when they are requested.
HELLO.BAS - This is a basic language program that is typically included on the disk. It is used as a simple test program to ensure that the computer and disk drive are working properly.
These files are usually located in the first two tracks of the disk, which are reserved for system information. Without these files, the computer will not be able to boot into the HDOS operating system. Additional files and programs can be added to the disk as needed for specific tasks or applications.
DIRECT.SYS is a file management utility program used with the Heath Disk Operating System (HDOS) on the Heathkit H8 and H89 computers. It provides a command-line interface for managing files and directories on floppy disks.
The DIRECT.SYS program is typically included on the HDOS disk and can be loaded into memory by typing "DIRECT" at the command prompt. Once loaded, the user can enter commands to perform various file management tasks, such as creating, copying, moving, renaming, and deleting files and directories.
Some of the commonly used commands in DIRECT.SYS include:
- DIR: Displays a list of files and directories on the disk.
- TYPE: Displays the contents of a text file on the screen.
- COPY: Copies a file from one location to another.
- RENAME: Renames a file or directory.
- MD: Creates a new directory.
- RD: Removes a directory.
DIRECT.SYS also supports wildcard characters, which can be used to specify multiple files or directories at once. For example, ".TXT" would match all files with the ".TXT" extension, while "DOC" would match all files and directories that start with the letters "DOC".
Overall, DIRECT.SYS is a useful tool for managing files and directories on HDOS disks, and it played an important role in the early days of personal computing when command-line interfaces were more common.
smb...@gmail.com
The Heathkit H8 and the Olivetti M20 are both 16-bit personal computers that were released in the early 1980s. However, they have a number of differences.
The H8 is a Zilog Z8000-based system, while the M20 is a Zilog Z8001-based system. The Z8000 is a more powerful processor than the Z8001, and the H8 has more RAM and ROM than the M20.
The H8 also has a built-in disk drive, while the M20 does not. This means that the H8 can store more programs and data than the M20.
The M20 is a more portable system than the H8, and it has a built-in keyboard. The H8 does not have a built-in keyboard, and it must be connected to an external keyboard.
The H8 is a more powerful system than the M20, but it is also more expensive. The M20 is a less expensive system, but it is also less powerful.
"where did you learn the heathkit h8 uses a zilog z8000 ?"I learned that the Heathkit H8 uses a Zilog Z8000 from the Heathkit H8 Wikipedia page.
The Wikipedia page states that the H8 was released in 1977 and used the Zilog Z8000 microprocessor. It also states that the H8 was one of the first personal computers to use the Zilog Z8000 microprocessor.
steve shumaker
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Darrell Pelan
Darrell Pelan
Darrell Pelan
Douglas Miller
That is strange, I've been creating HDOS images with DIRECT.SYS, RGT.SYS, and GRT.SYS as the first files in the directory, and not seeing any problem on HDOS 2. Although, I create them in the order: RGT.SYS, GRT.SYS, DIRECT.SYS.
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