Visopsys

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**Visopsys**
Website:	www.visopsys.org
Company/ developer:	Andy McLaughlin
Source model:	Open source
Latest stable release:	0.66 / February 01, 2007
Kernel type:	Monolithic kernel
License:	GPL
Working state:	Current

Visopsys (VISual OPerating SYStem) is a free software operating system for x86 personal computers available under the terms of the GNU General Public License (GPL). Like AtheOS, it was created entirely by a single hobbyist programmer, Andy McLaughlin. The development begun in 1997.

1 Features
2 VISOPSYS memory manager
3 VSH (also known as the Visopsys Shell)
4 External links

[edit] Features

Its own native graphical user interface.
Pre-emptive multitasking and multi-threading.
Supports FAT12/16/32 (read/write) and ext2/3 (read-only).
Supports NTFS, does not, however, does not support serial ATA hard disks.

[edit] VISOPSYS memory manager

The quantity of memory in a system is determined at boot time by the VISOPSYS operating system loader. This amount of memory is then passed to the kernel at startup.

In Visopsys, virtual memory is enabled, and uses a paging system to translate linear address to physical address, instead of using a segmented plus paging approach. The size of each page is 4KB, the same as the page table entries in most page table in most operating system.

4KB is chosen because it corresponds to the size of virtual memory page in the X86. Also, 4KB is relatively small compared to the large quantities of memory shipped with most modern PCs. This reduces the amount of waste. Large page entries result in memory waste due to internal fragmentation while page sizes that are too small result in a process having to refer to too many page table entries which is also a waste of space and CPU time, which is needed to translate the linear address to physical address.

[edit] VSH (also known as the Visopsys Shell)

This is the place where programmers can explore and make useful enhancement to the operating system. After making changes to any part of the .c files, compile them using the command "make" in Linux environment.