OS-X is a priority-based pre-emptive multitasking real-time embedded operating system designed for embedded Zilog Z80 systems with bank-switched memory. One of the main features of the OS-X is that it has the ability to run processes in separate address spaces (memory banks) and that allows a 8-bit Z80 to run an almost unlimited number of processes and host many software and data areas. The only limitation is that a part of the 64 KB memory space the CPU can address is reserved for common areas and that puts an upper limit on the size of each process. Kernel extensions exist for POSIX compliant file and thread services. It also has an optional file system using CMOS RAM, FLASH EPROM, floppy or remote storage media over network.

OS-X is distributed as a collection of precompiled object files and the corresponding interface source files.

OS-X is written in a combination of TML2 and Z80 machine code.