Re: ProDOS ?

[dempson@actrix.gen.nz (David Empson)]

KellihanB <kellihanb@aol.comDelete> wrote:

>    I'm just wondering what exactly ProDOS is for?  I know it's a Disk
> Operating System... but isn't the basic Apple II system able to read to
> and from a disk without loading a DOS first?

Not to any useful degree.

The Apple ][, ][+ and IIe have no built-in firmware to support disk
drives.

With a 5.25" disk controller card installed, the firmware on the card
provides bare minimum support for booting a disk: recalibrate the drive
head to track zero, read sector zero, and execute the code.

Other disk controller cards include more advanced code which allows the
operating system to read/write arbitrary blocks on the drive, and in
most cases low-level support for formatting a disk, but that's it.
These drivers deal with disks on a block (or sector) level, and have no
knowledge of file systems.

The IIc and IIgs have built-in firmware which provide the same functions
as disk controller cards for earlier machines, but don't provide any
more advanced features.

Everything that a user might want to do with a disk must be provided by
the operating system, whether that operating system happens to be DOS
3.3, ProDOS, Pascal, CP/M, GS/OS, or whatever.

The major functions provided by each operating system typically include:

- Extending the boot process to allow the operating system and startup
application to be loaded.

- Defining a file system.

- Providing support for applications to access disks at the file system
level.

- Providing a user interface which allows the user to manage their disks
and perform simple file operations (catalog, rename files, etc.).

- Utility programs may be included which provide more advanced features
such as copying files, formatting disks, etc.