[Coco] CoCo OS-9, a short simple explanation

Barry Nelson barry.nelson at amobiledevice.com
Mon May 16 19:01:39 EDT 2016

 In response to anyone who is totally new to and doesn't "get" OS-9, I would lie to offer these simple insights. OS-9 and NitrOS9 are disk operating systems, not a programming language, and is very similar to the following other disk operating systems in many respects…

Windows (when using the command line prompt)

Many programming languages are available to write programs under OS-9 and NitrOS9, including:

6809 assembly

Like Linux, Windows and MS DOS OS-9 manages files and folders, has a current directory and an execution path. Like Linux, OS-9 uses the / character to separate parts of a path as opposed to the \ used by Windows and MS DOS. OS-9 uses the chd command to change the currently active folder, in NitrOS9 you can use either chd, or cd exactly like Linux, MS DOS and Windows. The execution folder is set by the command chx in OS-9 and NitrOS9. These are called "built in" commands. Most other commands you might type are searched for in the current execution folder including the command dir which displays the contents of a folder. The command pwd displays the path to the current working folder, pxd displays the current execution folder path. The list command lists the contents of a text file. Unlike windows, OS-9 and NitrOS9 do not have "drive letters", instead they have device names. Typical device names are listed below…

/d0	Floppy drive 0, the first floppy drive
/d1	Floppy drive 1
/sd0	CoCo SDC drive 0
/sd1	CoCo SDC drive 1
/x0	DriveWire drive 0
/x1	DriveWire drive 1

A folder path might look like /d0/cmds, where /d0 indicates the floppy drive 0 and /cmds indicates the cmds folder on that drive. Like Windows and Linux, OS-9 and NitrOS9 have device drivers that must be installed to use different types of devices. To use the floppy drives, the floppy disk driver must be installed on the OS-9 or NitrOS9 disk that you booted with. Unlike Linux and Windows, however, both commands and device drivers can be loaded into memory and installed while the system is running using the load command. 

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