Sparta DOS X - Relation To Other DOS-es For Atari

Relation To Other DOS-es For Atari

Unlike its predecessor, SpartaDOS 3.0, SpartaDOS X is not what is commonly referred to as a "DOS" in Atari 8-bit parlance.

The Atari 8-bit Operating System consists of two main parts: the ROM-based "OS" and bootable "DOS". The common misconception about that division is that these respective parts correspond to BIOS and DOS on an IBM PC compatible machine. In reality the "OS" is responsible for communication not only with the block devices (like PC BIOS), but also for character devices, including file-oriented ones (like PC DOS). Consequently, all the file management functions are centralized in the "OS"-part, and the "DOS"-part is only one of its subordinated device drivers, that performs on a mass-storage media (like floppy disk).

A "DOS" for Atari, then, typically consists of the aforementioned device driver (called FMS, "File Management System"), and an application program playing the role of the OS shell. This shell is typically called DUP, "Disk Utility Package". All the communication between the user programs (including the DUP) and FMS goes through the CIO ("Central Input/Output") residing in ROM.

Such a design has some shortcomings, for example, no typical DOS is able to keep more than eight files opened at a time, because this is the limit imposed by the API of the ROM-based "OS".

Now SpartaDOS X, even though it is registered in the ROM-based CIO as a device driver and (for backward compatibility) performs all typical DOS functions as requested that way, is in fact independent of the CIO. Instead, it has own "I/O centre" (known as "the kernel"), not related to the ROM-based OS, with own set of specifiers and drivers for both character devices (like CON: or COM:) and block devices.

Under SpartaDOS X programs can perform all the I/O operations through the SpartaDOS kernel bypassing the Atari OS in ROM completely. Thanks to that it was possible to break many of its limitations: e.g. there can be as many as 16 files opened at a time. This also makes SpartaDOS X (unlike, for example, its predecessor SpartaDOS 3.2, or any other DOS for Atari) an operating system, not just another device driver with some sort of a shell.