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| SymbOS | |
|---|---|
 Screenshot of the SymbOS desktop on the Amstrad CPC | |
| Developer | SymbiosiS |
| Written in | Assembly language (Zilog Z80) |
| Working state | Current |
| Source model | Freeware |
| Initial release | 1 May 2006 |
| Latest release | 4.0 / 31 January 2025 |
| Available in | English |
| Supported platforms | Amstrad CPC, MSX, Amstrad PCW, Amstrad NC100, Amstrad NC200, Enterprise 64/128, ZX Spectrum Next, Virtual Machine |
| Kernel type | Microkernel |
| Default user interface | Graphical user interface |
| Official website | www |
SYmbiosis Multitasking Based Operating System (SymbOS) is a multitasking operating system for Zilog Z80-based 8-bit computer systems.
Unlike early 8-bit operating systems, SymbOS is based on a microkernel, which provides preemptive and priority-oriented multitasking and manages random-access memory (RAM) with a size of up to 1024 KB. It has a Windows-like graphical user interface (GUI), supports hard disks with a capacity of up to 128 GB and can already be booted on an unexpanded Amstrad CPC-6128, a 128K-MSX2 and an Amstrad PCW.
As of January 31, 2025, it is available for the Amstrad CPC, Amstrad PCW models, Amstrad NC series of computers, Enterprise 64/128, the ZX Spectrum Next, all MSX models starting from the MSX2 standard, MSX with V9990 graphics chip, CPC-TREX, C-ONE and as a Virtual Machine for running on modern hardware.[1]
SymbOS was originally started as an experiment to find out to what extent it is possible to implement a multitasking operating system with a windowed GUI on an 8-bit computer from 1985. GEOS contributed to the motivation, but the structure and features of SymbOS aren't similar to that system. The release in 2006 proved that such a "mini windows" system is possible on a then 20-year-old home computer with only quantitative limitations. SymbOS is one of the largest retro computing software projects of recent years. One of the goals of the project is to allow these old machines to be used like a modern PC, using hardware extensions.[2]
Although only an 8-bit CPU, the Z80 can run a preemptive multitasking operating system. Features such as memory protection, which the Z80 lacks, are not essential in such an OS. For example, AmigaOS also lacks memory protection. The MP/M OS proved that multitasking on the Z80 CPU was possible. Yet, it was generally unavailable for home computers.
While the MOS Technology 6502 cannot move the stack pointer, the Z80 can freely relocate it to any position in memory, which makes it easier to implement preemptive multitasking. The existence of an alternative register set accelerates context switching between tasks dramatically. [dubious – discuss]
The restriction of Z80 system to a 64 KB address space can be solved with bank switching. In this way, computers like the Amstrad CPC and PCW, MSX, Enterprise or SAM Coupé can access hundreds or thousands of kilobytes of memory.
SymbOS includes a microkernel, which can perform task management, memory management and inter-process communication.[3]
For task management, a combination of preemptive and cooperative multitasking was chosen, which makes different task priorities possible. Preemptive means that tasks are interrupted after a certain amount of time by the operating system, in order to share the CPU time with other tasks. Cooperatively means that a task stops using CPU time by itself. It does that, if it's finished with its current job or waiting for a certain event. Because of this combination it is possible to assign priorities. Tasks with low priority get CPU time only if all tasks with higher priorities are not then working.
Memory management divides the entire RAM into small 256 byte blocks, which can be assigned dynamically. Applications are always running in a secondary 64 KB RAM bank, where no memory space is occupied by the operating system or the video memory. That makes it possible to reserve up to 63 KB in one piece.
Banking management ensures that the system can administer memory with a size of up to one megabyte, even though the Z80 CPU has only a 16-bit address bus. It makes transparent access to memory and functions placed in other 64 KB banks possible.
Communication between different tasks and the operating system usually does not take place via calls, but is done via messages. This is necessary inside a multitasking environment to avoid organization problems with the stack, global variables and shared system resources. The SymbOS kernel supports synchronous and asynchronous IPC.
SymbOS supports the file systems CP/M, AMSDOS, and File Allocation Table (FAT) 12-16-32, on all platforms. For the latter, SymbOS can address mass storage devices with a capacity of up to 128 GB. Also, the ability to administer files with a size of up to 2 GB is uncommon for an 8-bit system. FAT support allows easy data exchange with other computers, as most 32 and 64 bit operating systems support the three FAT file systems.
The graphical user interface (GUI) of SymbOS works in a fully object-oriented manner. The look and feel mimics that of Microsoft Windows. It contains the well-known task bar with the clock and the "start" menu and can open up to 32 windows that can be moved, resized and scrolled. The whole system is written in optimized assembly language, meaning that the GUI runs as fast as the host machine supports.
Content of a window is defined with "controls" that are primitive GUI elements such as sliders, check boxes, text lines, buttons or graphics. The background or invisible areas of a window don't need to be saved in a separate bitmap buffer. If an area needs to be restored on the display, its contents will be redrawn instead.
There are several standard applications available for SymbOS, which are designed to resemble similar software available on other operating systems. Examples include Notepad, SymCommander (similar to Norton Commander), SymShell (cmd.exe), SymZilla (Mozilla Firefox), SymPlay (QuickTime), SymAmp (Winamp) and Minesweeper.[4]
Applications can be written for SymbOS in Z80 Assembler or Ansi C (using a native compiler) and can be assisted with the Quigs development IDE[5]
The following list of commands is supported by SymShell.[6]
SymbOS was originally developed for the Amstrad CPC. Its modular structure, with strict separation of general and hardware components, makes porting to other Z80-based systems with sufficient memory possible.
Release 1.0 (May 2006) was the initial release and supported the Amstrad CPC.
Release 1.1 (December 2006) added support for MSX2 computers.
Release 2.0 (August 2007) added a port for the Amstrad PCW.
Release 2.1 (August 2014) saw the support for additional MSX computers.
Release 3.0 (August 2017) added support for Enterprise 64/128.
Release 3.1 (December 2021) added additional hardware support for the platforms for video and mass storage.
Release 4.0 (January 2025) saw the addition of Amstrad NC series, ZX Spectrum Next and the Virtual Machine edition.
Versions for the SAM Coupé and such clones of ZX Spectrum as ATM-turbo 2+ and ZX-Evolution/BaseConf are possible, too, as they fulfill the requirements for SymbOS.
By keeping a basic condition for an operating system, the strict separation of hardware and application software by an intermediate layer, SymbOS applications run platform-independently on each computer and doesn't need to be adapted for different systems, with the obvious exception of applications that directly access particular hardware.
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Source: Wikipedia. Article content is retrieved live through the MediaWiki API.
SYmbiosis Multitasking Based Operating System (SymbOS) is a multitasking operating system for Zilog Z80-based 8-bit computer systems. Unlike early 8-bit operating systems, SymbOS is based on a microkernel, which provides preemptive and priority-oriented multitasking and manages random-access memory (RAM) with a size of up to 1024 KB. It has a Windows-like graphical user interface (GUI), supports hard disks with a capacity of up to 128 GB and can already be booted on an unexpanded Amstrad CPC-6128, a 128K-MSX2 and an Amstrad PCW. As of January 31, 2025, it is available for the Amstrad CPC, Amstrad PCW models, Amstrad NC series of computers, Enterprise 64/128, the ZX Spectrum Next, all MSX models starting from the MSX2 standard, MSX with V9990 graphics chip, CPC-TREX, C-ONE and as a Virtual Machine for running on modern hardware.
ren (or rename) is a shell command for renaming a file and in some implementations (such as AmigaDOS) a directory. Some shells with ren also provide a move command that provides for moving between directories. On systems that do not support a move command (such as MS-DOS older than 6.00), the user could copy a file to a new destination and then delete the original file. In DOSBox, ren can move files. The command is in various shells such as COMMAND.COM, Command Prompt, 4DOS, 4NT and PowerShell. In MS-DOS, the command is available in versions 1 and later. In PowerShell, ren is a predefined alias for the Rename-Item Cmdlet which serves the same essential purpose. Similar commands are available in many operating systems. The command is available in the CP/M, MP/M, Cromemco DOS, TRIPOS, OS/2, ReactOS, SymbOS, and DexOS. Multics includes a rename command to rename a directory entry, which could be contracted to rn. A rename command which in some cases can be contracted to ren is provided in Stratus VOS, RT-11, OS/8, RSX-11, ISIS-II, iRMX 86, TOPS-20, Z80-RIO, FLEX, OS-9, FlexOS, 4690 OS, MPE/iX, THEOS/OASIS, and OpenVMS A rename command is supported by 86-DOS. DR DOS 6.0 includes ren and rename commands. PC-MOS includes an implementation of rename. It is also available in the MS-DOS emulator DOSBox.
The Amstrad CPC (short for "Colour Personal Computer") is a series of 8-bit home computers produced by Amstrad between 1984 and 1990. It was designed to compete in the mid-1980s home computer market dominated by the Commodore 64 and the ZX Spectrum; it successfully established itself primarily in the United Kingdom, France, Spain, the German-speaking parts of Europe, and also Canada. The series spawned a total of six distinct models: The CPC 464, CPC 664, and CPC 6128 were highly successful competitors in the European home computer market. The later 464 plus and 6128 plus, intended to prolong the system's lifecycle with hardware updates, were considerably less successful, as was the attempt to repackage the plus hardware into a game console as the GX4000. The CPC models' hardware is based on the Zilog Z80A CPU, complemented with either 64 or 128 KB of RAM. Their computer-in-a-keyboard design prominently features an integrated storage device, either a compact cassette deck or 3-inch floppy disk drive. The main units were only sold bundled with either a colour, green-screen or monochrome monitor that doubles as the main unit's power supply. Additionally, a wide range of first and third-party hardware extensions such as external disk drives, printers, and memory extensions, was available. The CPC series was pitched against other home computers primarily used to play video games and enjoyed a strong supply of game software. The comparatively low price for a complete computer system with dedicated monitor, its high-resolution monochrome text and graphic capabilities and the possibility to run CP/M software also rendered the system attractive for business users, which was reflected by a wide selection of application software. During its lifetime, the CPC series sold approximately three million units.
The Zilog Z80 is an 8-bit microprocessor designed by Zilog, first released in 1976; it played an important role in the evolution of early personal computing. It was designed to be software-compatible with the Intel 8080, offering a compelling alternative due to its better integration and increased performance. Along with the 8080's seven registers and flags register, the Z80 introduced an alternate register set, two 16-bit index registers, and additional instructions, including bit manipulation and block copy/search. Originally intended for use in embedded systems like the 8080 was, the Z80's combination of compatibility, affordability, and superior performance led to widespread adoption in video game systems and home computers throughout the late 1970s and early 1980s, helping to fuel the personal computing revolution. The Z80 was used in iconic products such as the Osborne 1, Radio Shack TRS-80, ColecoVision, ZX Spectrum, Sega's Master System and the Pac-Man arcade cabinet. In the early 1990s, it was used in portable devices, including the Game Gear and the TI-81 and succeeding graphing calculators. The Z80 was the brainchild of Federico Faggin, a key figure behind the creation of the Intel 8080. After leaving Intel in 1974, he co-founded Zilog with Ralph Ungermann. The Z80 debuted in July 1976, and its success allowed Zilog to establish its own chip factories. For initial production, Zilog licensed the Z80 to U.S.-based Synertek and Mostek, along with European second-source manufacturer, SGS. The design was also copied by various Japanese, Eastern European, and Soviet manufacturers gaining global market acceptance as major companies like NEC, Toshiba, Sharp, and Hitachi produced their own versions or compatible clones. The Z80 continued to be used in embedded systems for many years despite the introduction of more powerful processors, and remained in production until 2024, 48 years after its original release. Zilog also continued to enhance the basic design of the Z80 with several successors, including the Z180, Z280, Z380, and eZ80.
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
MORE →Mae Jemison, aboard Space Shuttle Endeavour in 1992.
