Fifth - virtual machine, operating system, programming language
Table of Contents
1. General
- This program is free software: released under Creative Commons Zero (CC0) license
- Program author:
- Svjatoslav Agejenko
- Homepage: https://svjatoslav.eu
- Email: mailto://svjatoslav@svjatoslav.eu
- Other software projects hosted at svjatoslav.eu
1.1. Source code
- Download latest snapshot in TAR GZ format
- Browse Git repository online
Clone Git repository using command:
git clone https://www2.svjatoslav.eu/git/fifth.git
2. !Project deprecated!
Current implementation does not support object oriented programming. While working on Fifth I got lots of cool new ideas that require reimplementation of everything.
Currently I try to implement those new ideas in the project called Sixth.
System is built many years ago when I was still using DOS as a primary operating system.
3. Introduction
Fifth is a combination of:
- Programming language (inspired by Forth).
- Operating system.
- Virtual machine with custom instruction set.
3.1. Screenshots
Startup screen diplaying Fifth logo and full file list.
Sample words defined. Most of the words are commands that can be executed interactively from the command line or from a file. When executed, they can be selectively compiled or interpreted.
Built in text editor.
4. Installation
Just unpack all files, witout altering original directory structure, somewhere in your hard disk. For example:
C:\MISC\FIFTH\
To run fifth you need minimally just 2 files:
- EMULATOR.COM
- Virtual CPU emulator
- DISK.RAW
- Virtual disk file
For more information, please refer to Fifth distribution directory tree description.
5. Fifth distribution directory tree description
After downloading and unpacking the ZIP file you shoud get directory tree similar to this:
DOC - Fifth documentation
commands - documentation on Fifth built-in commands
modules - documentation on additional commands, realized as loadable modules
shots - Fifth screenshots
imageFile - files contained within 'disk.raw', just an extracted form.
source - source files
emulator - emulator source
util - utilites
disk.raw - Virtual disk file, has filesystem inside.
emulator.com - main executable.
6. Requirements
6.1. Software
- MS-DOS 6.22 with HIMEM.SYS loaded.
- Mouse driver (optional, if you have a mouse).
- CPU is initialized into Unreal Mode during operation.
- To recompile ASM sources, you can use FASM (Flat Assembler).
- To run Quick Basic utilities, use Microsoft Quick Basic 4.5.
- VESA support through BIOS or external driver (UNIVBE).
6.2. Hardware
- A minimum of a i386 CPU.
- 64 KB of free RAM below 640KB.
- 2 MB of free extended memory.
- A VESA-compatible video card.
7. Numbers representation within Fifth
Because we are in full experimentation mode here (no regard for compatibility whatsoever), why not to try also alternative number representation ?
Here alternative hexadecimal number representation format is devised:
Essentially square is split into 4 triangles. Each triangle represents one bit.
Fifth uses this hexadecimal format as primary throughout entire system.
See also: Bibi-binary.
8. Disk file map, and it's data structures
Core and high-level boot code is stored outside of the filesystem to allow easy access to it, at early booting time, when filesystem is not yet initialized.
8.1. Disk allocation
| offset | length | description |
|---|---|---|
| 0 | ~4 Kb | Fifth core |
| 4 Kb | ~32 Kb | high-level boot code |
| 37 Kb | ~65 Kb | FAT |
| 101 Kb | ~16 MB | filesystem data area |
8.2. FAT entry format:
| code | meaning |
|---|---|
| -2 | last sector |
| -1 | empty sector |
| 0 -- | .. pointer to next block |
8.3. File entry format
| offset | length | description |
|---|---|---|
| 0 | 4 | extension |
| 4 | 16 | name |
| 20 | 4 | entry point |
| 24 | 4 | size |
| 28 | 4 | last modification time |
9. Core architecture
Fifth core is simply some amount of already compiled into machine code and linked together modules (entries in other words). In compilation process modules is compiled one by one and simply stored on top of already existing and growing core. Separately from core is kept dictionary, this is special list that contain names of compiled modules, variables etc. and they locations in core. Constants use dictionary space only. Random word can be removed from dictionary at any time. Currently dictionary can contain at most 1000 entries.
9.1. Dictionary entry format
| offset | length | description |
|---|---|---|
| 0 | 4 | 0 < previous entry |
| 0 = last | ||
| -1 = empty | ||
| 4 | 15 | module name string |
| 19 | 1 | entry type |
| 20 | 4 | entry data |
Core headers as linked list of module names make up something like dictionary. When some entry address is needed compiler can quickly run through headers backwards and find needed entry.
9.2. Possible module types
| type | description | "execute" action |
|---|---|---|
| 0 | data | compile "num" instruction |
| with address to module | ||
| 1 | submodule | compile "call" instruction |
| with address to module | ||
| 2 | imm. submodule | immediately call to module |
9.3. Memory map
| location | size | description |
|---|---|---|
| 0 | ~4096 | core |
| 1500000 | ~32000 | highlevel Fifth boot code |
| 200000h | core startup messages area | |
| 5200000 | end of dynamic memory space |
10. Dynamically loadable modules
10.1. Keyboard driver
KBD_@ ( – code ) get scancodes for pressed keys from keyboard.
KBD_down? ( key – result ) check is key with specified scancode
currently pressed down.
KBD_SC2FSCII ( code – FSCII ) convert key scancode into FSCII code,
or in FSK (Fifth standard keycode).
KBD_F@ ( – FSCII ) read pressed key FSCII or FSK, returns -1 if no
keys are pressed.
KBD_FW@ ( – FSCII ) read pressed key FSCII or FSK, if no keys is
are pressed then waits until there is.
FSK
—
In HEX.
FC backspace
FD TAB
FE enter
FF space
400 ESC
401 … F1 …
410 up
411 right
412 down
413 left
414 INS
415 DEL
416 home
417 end
418 PG/UP
419 PG/DN
10.2. Mouse driver
mousex var Mouse x coordinate.
mousey var Mouse y coordinate.
mousekeyl var Mouse left key.
mousekeym var Mouse middle key.
mousekeyr var Mouse right key.
mousec var Display current mouse coordinates in top left part of screen,
if true. (good for debugging)
mousepointer var Image buffer, holding current mouse pointer.
mouseadd ( ModuleAddr x1 x2 y1 y2 – ) Add specified area on screen,
into mause click buffer. If any mouse button is clicked on
that area, module at "ModuleAddr" will be executed.
mousebe var Amount of buffer elements.
mousedo ( – ) Updates mouse coordinates and keys. Parse mouse
click buffer, and draw mouse cursor to "screen".
10.3. 2D graphic library
- lineh ( color len x y imgbuf – )
- draws horisontal line from X,Y coordinates to right, with specified length.
- linev ( color len x y imgbuf – )
- draws vertical line down, from coordinates X,Y, with specified length.
- box ( color x2 x1 y2 y1 imgbuf – )
draws rectangular box. x2 bust be >= x1, y2 must be >= y1.
x1,y1-----------+ | | | | +-----------x2,y2
- flipv ( imgbuf – )
- flip image vertically.
- imgcoltrans ( ImgBuf Color ToColor – )
- Translate all pixels in specified image with "Color" into "ToColor".
- imgfill ( color x y imgbuf – )
- Fill image region starting at location X & Y with specified color.
10.4. Trigonometry functions
10.4.1. sin ( a – result )
Return sinus from given angle "a", 360ø is 2000. So 1000 represents 180ø angle. Result will be in range -10'000 to 10'000, instead of ñ1.
10.4.2. cos ( a – result )
Return cosinus from given angle. Parameters are like in sin function.