From DOSpedia

ZDOS is a 32-bit real time OS for the X86 CPU family, written entirely in assembly language for maximum performance by Zebor Technology.

ZDOS was developed as a 32-bit replacement of 16-bit DOS, but with modern features like multi tasking, demand paging, SMP etc..

As a BIOS vendor we also integrated a complete 32-bit BIOS within ZDOS, in order to give programmers similar flexibility & freedom they get with using DOS. With ZDOS you can do every thing you used to do, but now in a full 32-bit, multitasking environment. You can create 32-bit, multi tasking processes with a lot of threads, invoking safe reentrant 32-bit BIOS and DOS API calls.


ZDOS is fully backward compatible with 16-bit applications using BIOS and DOS APIs. These BIOS and DOS calls are handled entirely by 32-bit code, leaving more memory available between 640K to 1MB, since ZDOS maps locations used by the 16-bit BIOSes to upper memory blocks.

Old 16-bit applications runs in their own virtual machines in parallel with 32-bit processes.

Development tools

ZDOS comes bundled with the Open Watcom tool chain and includes everything needed to develop applications in C, C++ and assembly.

For your convenience, the tool chain can be run in both ZDOS and Windows host environments.

Our powerful C run time libraries, covering every 32-bit BIOS, DOS or kernel function are also included as a complement to the standard libraries.

The source level debugger can be run remotely using TCP/IP, UART or other connections.

As Open Watcom is open software, you will have full source on the complete tool chain, including our custom run time libraries.