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Already in the 80's, only few years after the release of the Commodore C64, the legendary GEOS by Berkeley Softworks appeared and set the standard for a windows-based operating system on c64. It was a graphical user-interface (GUI) which was similar to the old desktop of the Apple Macintosh. Powerfull applications were made available for GEOS like GeoWrite (similar to MS-Word) or GeoCalc (similar to MS-Excel). It was incredible, that an 8bit-machine with only 64K was able to realize such an operating system!

On the Amstrad CPC many efforts to build a decent GUI were made as well. In most cases they were just extensions to realize a WIMP (Windows, Icons, Menus and Pointers) environment but weren't true operating systems with their own kernel, memory-management and so on. The CEUS Desktop 2.0 (1990) by Prodatron was just such an extension-system.

Therefore, the CPC's own OS (in combination with AmsDOS) and CP/M were the only two known OSes for the series, but the question remained: since most CPCs have 128K (most C64 only have 64K), a screen-resolution of 320x200 with 4 colours (C64 only has 2 colours for each 8x8 area in 320x200) and some more advantages, why not have something similar? So the SymbOS-Project was born. SymbOS stands for "SYmbiosis Multitasking Based Operating System". SymbOS is a demonstration of what has been achieved on the CPC: real preemptive multitasking, dynamic memory-management for up to 576K and a totaly MS-Windows-like GUI are the three most important features.

SymbOS started being developed by Prodatron in November 2000 (more details on the development needed)


  • Micro kernel
    • Maximum amount of supported RAM: 576 KB
    • Maximum number of processes 32
    • Number of different process priorities 9
    • Maximum number of timers 32
    • Maximum number of open messages 64
  • System manager
    • Maximum number of applications 16
    • Maximum application core size 63 KB
  • Desktop manager
    • Maximum number of windows 32
    • Maximum number of controls per window 1000
    • Maximum possible screen resolution 16.000 x 16.000 pixel
  • File manager
    • Maximum hard disc size 128 GB
    • Maximum file size 2 GB
    • Maximum number of devices 8
    • Maximum number of open files 8
  • Source code
    • Source code size (OS Release 1) ~ 30.000 lines
    • Source code size (Applications) ~ 34.000 lines
    • Total size of the Z80 source code ~ 64.000 lines

Note: This is an edited version of the original SYMBOS site.