[continued from previous message]

- User programs to substitute for OS routines

INPUT/OUTPUT SUBSYSTEM
Multi-layered provision for user program access to hardware peripherals.
Device Handlers may be added by user programs. Includes a complete Cassette
Handler and a rudimentary Diskette Handler, but notably does not include a
complete Disk Operating System. Described in greater detail in a separate
section of this FAQ list.

REAL TIME PROGRAMMING
Hardware timers and system software timers are provided to facilitate
predictable and controllable speeds of software routine execution.

ROM CHARACTER SET
Atari ASCII, or ATASCII. May be substituted by user programs. Described in
greater detail in a separate section of this FAQ list.

FLOATING POINT PACKAGE (FPP)
Set of mathematical routines that use binary coded decimal (BCD) arithmetic
to provide standard mathematical functions (+, -, *, /), exponential and
logarithmic functions as well as conversion from ATASCII to BCD and BCD to
ATASCII. Developed apart from the rest of the Atari OS by Shepardson
Microsystems, Inc. (SMI) for internal use by Atari BASIC, but placed in
operating system ROM by Atari for universal availability.

Software can reliably determine the version of the Atari Operating System running as follows. (primary source: OS Manual XL Addendum, p.28)

First, determine whether the system is running a 400/800 OS version or an
XL OS version by checking the value of memory location $FCD8. In Atari
BASIC, PEEK(64728) is the equivalent test.
Read Result Means
$A2 (162) 400/800 OS
$4C (76) XL OS

Then, if running a 400/800 OS version as determined above, now check the
values of BOTH memory locations $FFF8 and $FFF9. In Atari BASIC, PEEK(65528) and also PEEK(65529) and interpret the results as follows:
$FFF8 (65528) $FFF9 (65529) 400/800 OS Rev. Rev. Date
------------- ------------- --------------- ---------
$FF (255) --> "Operating System 255"1979-04 (VERY RARE)
$DD (221) $57 (87) --> Rev.A/NTSC 1979-06 (uncommon)
$D6 (214) $57 (87) --> Rev.A/PAL 1979-06 (common)
$F3 (243) $E6 (230) --> Rev.B/NTSC 1981-09 (common)
$22 (34) $58 (88) --> Rev.B/PAL 1981-09 (NOT SHIPPED?)

About "Operating System 255" --
A pre-production demo unit release, possibly a few thousand once existed.
For more info see https://mcurrent.name/os255/410insert-os255.htm and
https://mcurrent.name/os255/softside.htm and the 17-Nov-79 essay
Atari_CASSETTE_TAPES.pdf found in post #2 in:
http://atariage.com/forums/topic/204930-some-early-atari-a8-development-docs/

If running an XL OS version as determined above, the Revision number of the XL OS is available at memory location $FFF7. In Atari BASIC, PEEK(65527) for the XL OS Revision number. XL OS Revisions released:
XL OS (Dec.) Hex Rev. Date Shipped in
Rev.A (10) $0A 1982-10-26 1200XL (all)
Rev.B (11) $0B 1982-12-23 - (rarely installed in serviced 1200XLs)
Rev.1 (1) $01 1983-03-11 600XL (early/most) / 800XL (earliest)
Rev.2 (2) $02 1983-05-10 600XL (later) / 800XL/65XE/130XE (most)
Rev.3 (3) $03 1985-03-01 65XE/130XE (late) / 800XE (all)
Rev.4 (4) $04 1987-05-07 XE System console (all)
Rev.3B (59) $3B 1987-07-21 65XE Najm (earlier)
Rev.3B (59) $3B 1987-07-21 09/22/88 - 65XE Najm (later)

OS MANUALS FROM ATARI (FPP coverage included)
- Operating System User's Manual
- Author: Harry B. Stewart, NEOTERIC for Atari
- (c)1980 edition
- GREEN title page (printings with line-printed title page include
printing date imprint; printing with Atari logo on title page lacks
printing date)
- 215 numbered pages
- Table of contents lacks page numbers
- Contents of pages numbered 191 and 192 are reversed
- The last two sections are:
pp. 177-199 Appendix K. OS Database Variable Functional Descriptions
pp. 200-215 Appendix L. Equate File (400/800 OS Rev.A source excerpt)
- Included in earlier printings of C016555 Atari Personal Computer
System Operating System User's Manual and Hardware Manual (official
nickname: "Technical User's Notes"), including printings dated:
November 1980 (orange cover page), August 1981 (cover page??)
- (c)1980 Rev. 0.2 edition
- GREEN title page (line-printed)
- 261 numbered pages
- Identical to the earlier (c)1980 edition through page number 191
- Confusingly, this includes the portion of the superseded version
of Appendix K from the earlier edition on pages numbered 177-191
- Pages marked 192 through 261 marked: "C016555 - Rev. 0.2"
- Pages 192-197: Appendix K. Device Characteristics
(content not included in the earlier edition)
- Pages 198-261: Appendix L. OS Database Variable Functional
Descriptions
(complete revision of the Appendix K. from the earlier edition)
- The Appendix L. Equate File content from the earlier edition is not
included.
- Included in January 1982 printing of C016555 Atari Personal Computer
System Operating System User's Manual and Hardware Manual (official
nickname: "Technical User's Notes") (yellow cover page)
- (c)1982 edition
- GRAY title page (with Atari logo)
- 273 numbered pages
- Completely revised table of contents, including page numbers
- Completely revised layout; content is heavily revised in some places
- Includes Index (pages 271-273)
- Included in C016555 Rev. A (1982) Technical Reference Notes
- De Re Atari: A Guide to Effective Programming
- C060070, (c)1981 edition (early version for registered developers)
https://archive.org/details/DeReAtari_early_version
- APX-90008, (c)1982 edition (common version sold via APX)
http://www.atariarchives.org/dere/
- Also published in German and French language editions
- Operating System Manual: Supplement to Atari 400/800 Technical Reference
Notes C024515 (ii+38 pages covers changes from the 400/800 OS to the XL OS)
- REV. A with green cover: "Atari 1200XL: Atari Home Computer System"
- White cover: "Atari XL Addendum: Atari Home Computer System"
- Author (uncredited): Robert A. Peck

OS SOURCE CODE PUBLISHED BY ATARI
(excluding the FPP; see "What is Atari BASIC" FAQ section for FPP source code)
- Operating System Source Listing C017893 / CA016557 (order#)
- August 1981, (c)1981
- "This is the original June 1979 Atari 400/800 computer operating system
listing" (page 1)
- 131 numbered pages (5785 lines) + 24 un-numbered pages (Cross Reference)
- Operating System Source Listing, (c)1982
- "This is the modified September Atari 400/800 computer operating system
listing" (page 1)
- "This is the Revision B EPROM version" (page 1)
- 129 numbered pages (5805 lines) + 24 un-numbered pages (Cross Reference)
- Included in C016555 Rev. A (1982) Technical Reference Notes
- According to Mapping the Atari, Revised Ed. by Ian Chadwick, page 212, or
http://www.atariarchives.org/mapping/appendix12.php :
"Atari did produce a listed source code for the XL OS, although for some
reason it was never published for public sale as it was intended...It is
an excellent 500+ page resource document."

OS DEVELOPER CREDITS AT ATARI
(see "What is Atari BASIC" FAQ section for FPP credits)

400/800 OS
Rev.A
David Crane - Design/programming -
graphic assistance routines (line draw, area fill)
(also wrote: APX Outlaw/Howitzer)
Alan Miller - Design/programming
(also wrote: Basketball)
Larry Kaplan - Design/programming
(also wrote: Video Easel, Super Breakout)
Harry B. Stewart - Design (as Neoteric consultant to Atari)
(also wrote: APX Extended WSFN, Atari PILOT)
Gary Palmer - Worked on the I/O portion (as consultant to Atari)
Ian Shepard - Developed the disk drive functions
R. Scott Scheiman - ATASCII

Rev.B
Michael P. Mahar - Fix several problems
R. Scott Scheiman - Fix several problems

XL OS
Rev.A
Harry B. Stewart - External Reference Specification
(Neoteric consultant to Atari)
Lane Winner - ?
R. Scott Scheiman - Handler Loader
Y. M. (Amy) Chen - Relocating Loader; International Character Set
Mike W. Colburn - Self Test
Richard K. (Hud) Nordin - ?

Rev.B
R. Scott Scheiman - Fix several problems

Rev.1
R. Scott Scheiman - Support for PBI and on-board BASIC
Richard K. (Hud) Nordin - Support for PBI and on-board BASIC
Y. M. (Amy) Chen - Support for PBI and on-board BASIC

Rev.2
R. Scott Scheiman - Fix several problems

Rev.3
? - Self Test updated; Fix one problem

Rev.4
? - Support for detachable keyboard and on-board game

Rev.3B
? - Arabic character set and right-to-left text entry

Source code and further details for all known shipped and prototype versions
of the Atari OS, based on disassembled ROM images combined with published source listings, was (amazingly) published by Tomasz Krasuski at http://www.atariage.com/forums/topic/201133-os-source-code-all-revisions/

------------------------------

Subject: 7.1.2) What modified versions of the Atari OS were released?

This should be a complete list of modified versions of the Atari operating system ROM chips, or extensions to the OS released on ROM chips, released commercially by third-parties for the Atari.

Replacement personality boards for the 800, as well as 400/800 OS "translator" programs distributed as software, are listed in separate sections of this FAQ list.

Countless public domain modifications to the Atari OS have been produced as well. These are generally not listed here.

For the 400/800
---------------
Fastchip (or: Fast Chip), by Charles W. Marslett for Newell Industries, 1981
- Faster replacement for the Floating Point Package (FPP) ROM chip
(Analog #8p93)
- Source code available:
http://www.wordmark.org/mydos.html (Revision C, 30 November 1981)

Supermon!, by CDY Consulting (David Young), 1982?
- Resident machine language monitor
- Installs into the 4KiB byte block of memory at $C000.
- Shipped with earliest Ramrod units by Newell Industries
- For later released versions see: Omnimon! (1983?)

Omnimon!, by CDY Consulting (David Young), 1983?
- Resident machine language monitor
- For earliest released version see: Supermon! (1982?)
- Installs into the 4KiB byte block of memory at $C000.
- Standard Version (4KiB): Has a HELP command (not present in other versions)
- Shipped with Omnimon! piggyback board by The Peripheral Connection
(Bill Williams)
- Shipped with Newell Industries Ramrod personality board (800)
- Advanced Version A (4KiB): Adds several utilities, plus support for
Happy 810 Enhancement and Bit 3 Full-View 80
- Ramdisk Version R (4KiB): Most features of Advanced Version A, including
Happy 810 Enhancement and Bit 3 Full-View 80 support, plus RAM drive for
Axlon banked memory
- Banked Version L (4KiB): Same as Ramdisk Version R with additional disk I/O
facilities, but without debugging commands of Standard Version
- Banked Version U (4KiB): Designed to complement Banked Version L. Includes
debugging commands of Standard Version plus a mini-assembler and a
relocate command.
- 8K Omnimon! (1984)
- Supplied on an 8KiB chip with hardware toggle switch used to select
between Version L and Version U. Characters on the screen are inverted
to prompt the user to flip the switch when needed.
- Standalone 4KiB Versions A/R/L/U were discontinued at the release of
8K Omnimon!; the 4KiB Standard Version would initially remain available.

OSN (O.S.'N'), by Wes Newell for Newell Industries, 1983
- Complete replacement 400/800 operating system
- Shipped with Newell Ramrod 800 personality board (except "Ramrod 3")
- OSN supplied on 2 4KiB chips or on one 8KiB chip.
- Provides all graphics modes, including modes 12-15 that are not in the
standard 400/800 OS
- Cassette interface is programmable to any baud rate
- Keyboard delay and repeat functions have been modified to allow for
faster typing and cursor movement.
- Cartridges can be disregarded on power up.

Omniview (Omniview 400/800), by CDY Consulting, 1984
- Adds 80 column E: and S: OS device drivers, using 3-bit wide characters
in ANTIC mode F (BASIC GR. 8). Software can also be optimized to write
to the Omniview screen output routines.
- RAM drive for Axlon banked memory (up to 1MiB).
- Installs into the 4KiB byte block of memory at $C000.
- Two versions: Omniview standard (4KiB) or 8K Omniview.
- 8K Omniview consists of Omniview standard (4KiB) version + CDY Omnimon!
standard (4KiB) version in an 8KiB bankable ROM.
- On a CDY Omnimon! board, the Omniview chip replaces the Omnimon! chip
- On Newell Ramrod board, the Omniview chip either replaces the Supermon!/
Omnimon! chip, or it can be installed alongside the Supermon!/Omnimon! chip
through the use of a hardware toggle switch.
- Many units supplied with SpeedScript 80 (earlier name) / OmniWriter (later
name), OmniTerm (modified VT-10-Squared), and patch instructions for Bit 3
Full-View 80 supporting versions of LJK Letter Perfect and LJK Data Perfect. - Sold separately by CDY: Patched AtariWriter Plus (130XE version), OmniCom
(commercial versions for Omniview)

ROMDOS / RDOS, by Wordmark Systems
- Equivalent to MYDOS 3.0 (described elsewhere in this FAQ list)
- Installs into the 4KiB byte block of memory at $C000.
- For Newell Ramrod personality board or CDY Omnimon! board

OMNIDOS, by CDY Consulting / Wordmark Systems
- Wordmark ROMDOS/RDOS (4KiB) and CDY Omniview standard (4KiB) on one 8KiB
chip
- Installs into the 4KiB byte block of memory at $C000.
- For Newell Ramrod personality board or CDY Omnimon! board

Impossible!, by Computer Software Services (CSS), 1984
- 4K Static RAM-Pac board plugs in place of the C012499 OS ROM chip
- Adds 4KiB RAM at $C000, hardware switch selectable
- Shipped with disk containing copying software

Ultimon, by Computer Support, 1986
- Machine code monitor/disassembler, mini-DOS, disk sector editor

80 Column Pack, by Computer Support, 1986
- 80 column text mode using a Graphics 8 screen

Superchip / Super-Chip, by Computer Support, 1986
- Fast floating point math routines ?????

For the 800 only
----------------
Super800, by Super Products
- Piggyback board for CX801 personality board
- Run the 400/800 OS or the XL OS
- Includes Supermon, by Super Products
- 2 hardware switches: XL emulation on/off, Supermon on/off
- Includes 16KiB RAM
- Can use Super Products SuperRAM (800 version)
- Used as Axlon banked memory when running the 400/800 OS
- Used as Port B banked memory when running the XL OS

For the 600XL/800XL/65XE/130XE/800XE (not 1200XL/XEgs unless specified) ------------------------------------
XL Fix ROM, by Computer Software Services (CSS), 1984
- 400/800 OS translator
- Access to 4KiB RAM at $C000
- Available for 1200XL or for 600XL/800XL
- Board includes socket for standard XL OS ROM chip, and includes switch
for selecting XL OS or 400/800 OS.

XL Boss, by Allen Macroware, 1984
- 400/800 OS translator in ROM
- Access to 4KiB RAM at $C000
- OS ROM chip for 800XL/600XL, or chip with adapter for 1200XL
- Beginning 1985 shipped with dual operating system board
- Shipped with (disk):
MacroMon XL (machine language monitor), MacroDOS (miniature DOS)

OmnimonXL, by CDY Consulting, 1984
- Single OS ROM chip includes:
- OSNXL (OSN XL/XE) operating system
- Fastchip XL floating point routines
- OmnimonXL (Omnimon XL) resident machine language monitor
- Compatible with the 400/800 OS, but has a programmable cassette baud rate,
increased keyboard speed, and all the graphic modes of the XL/XE's
- Shipped with Newell Industries Ramrod XL (Ramrod XL/XE)(except "Ramrod XL2")
(Ramrod XL board plugs in place of the OS ROM chip; has 3 XL/XE ROM sockets
and hardware OS select switch)

OmniviewXL, by CDY Consulting, 1984
- Single OS ROM chip includes:
- OSNXL (OSN XL/XE) operating system
- Fastchip XL floating point routines
- OmniviewXL (Omniview XL/XE)
- Compatible with the 400/800 OS, but has a programmable cassette baud rate,
increased keyboard speed, and all the graphic modes of the XL/XE's
- Adds 80 column E: and S: OS device drivers, using 3-bit wide characters
in ANTIC mode F (BASIC GR. 8). Software can also be optimized to write
to the Omniview screen output routines. Compatible with Omniview 400/800.
- Built-in ATRMON terminal emulator for use with the ATR8000
- Later versions (Omniview XL/XE) include 64KiB RAM drive for 130XE banked
memory
- Supplied with SpeedScript 80 (earlier name) / OmniWriter (later name),
OmniTerm (modified VT-10-Squared), and patch instructions for Bit 3 Full-
View 80 supporting versions of LJK Letter Perfect and LJK Data Perfect.
- Sold separately by CDY: Patched AtariWriter Plus (130XE banked memory
version), OmniCom (commercial versions for Omniview)

Bibomon, by Erwin Reuss for Compy-Shop, 1984
- Later known as: "4K-Bibomon"
- XL OS with added machine language monitor
- Includes piggyback socket for standard XL OS chip and hardware switch

512K RAM BetriebsSystem Chip, by Irata Verlag, 1985?
- XL OS with added RAM drive support for the company's
512K RAM 800XL RAMFloppy

High Chip XL, by Irata Verlag, 1985
- XL OS with added buffered fast write with verify SIO for use with the
company's High Speed Board 1050 (Happy 1050 Enhancement clone)

High Chip XE mit RAMDisk, by Irata Verlag, 1985?
- High Chip XL with added RAM drive for 130XE banked memory

OldRunner Chip, by Irata Verlag, 1985?
- 400/800 OS translator in ROM

Supermon, by Will Visser for Super Products, 1985
- 400/800 OS translator, with enhancements
- Disassembler; DOS functions; 4 color screen dump
- Also included with Super Products Super800

XOS/80 Column Pack!, by Computer Support, 1985
- 600XL/800XL and 130XE banked memory separate versions
- XL OS modified to be highly compatible with the 400/800 OS, plus 820 baud
cassette saves
- 80 column text mode using a Graphics 8 screen

XOS/Ultimon!, by Computer Support, 1985
- 600XL/800XL and 130XE banked memory separate versions
- XL OS modified to be highly compatible with the 400/800 OS, plus 820 baud
cassette saves
- Machine code monitor/disassembler, mini-DOS, disk sector editor http://ultimon.com/

XOS/Fix, by Computer Support, 1985
- 400/800 OS translator in ROM

Superchip / Super-Chip, by Computer Support, 1986
- 600XL/800XL and 130XE banked memory separate versions
- XL OS with fast floating point math routines ?????

Ultra Speed OS, by Computer Software Services (CSS), 1986
- Universal support for high speed read/write with upgraded disk drives
including Klone/Happy, Duplicator, and US Doubler
- Numerous other OS enhancements
- Chip shipped with piggyback socket and switch for hardware toggle between
Ultra Speed OS and standard Atari XL OS

Omniview 256, by CDY Consulting, 1986
- Omniview XL/XE (see OmniviewXL above) with added 192KiB RAM drive for
Port B banked memory
- Marketed for use with 800XL with Newell Industries 256KXL upgrade

16K-Bibomon, by Erwin Reuss for Compy-Shop, 1986
- Add on board includes:
- Bibomon 16K machine language monitor ROM
(occupies 4KiB address space at $C000)
- Oldrunner 400/800 OS ROM chip
- Socket for standard XL OS ROM chip
- Hardware clock
- Centronics compatible printer port
- Hardcopy Routine: Epson FX-80 and Okidata Microline compatible
- mini-DOS: DOS 2.5 and OSS DOS XL compatible, plus Speedy 1050 high speed
- Hardware switches used to select between XL OS / Oldrunner, between
BASIC On / BASIC Off under Oldrunner, and between Bibomon or
International character set under Oldrunner

QMEG-OS V3 (c)'87 S.Dorndorf (1987)
- "Quarter-Mega Operating System"
- For computers with 192KiB of Port B banked memory (256KiB total system RAM)
- Three RAM drive configurations supported:
1) Two RAM drives of 90KiB each (emulated SS/SD floppy disk drives)
2) One RAM drive of 128KiB (emulated SS/ED floppy disk drive),
one RAM drive of 64KiB (compatible with the DOS II+/D v6.x RAM drive)
3) One RAM drive of 180KiB (emulated SS/DD floppy disk drive)
- Supports supplementary RAM drive of 5.25KiB dedicated to storage of DOS.
- Intended for use with DOS II+/D v6.x
- High speed support: US Doubler/UltraSpeed, Happy/Warp Speed
- Machine Language Monitor (MLM) with disassembler
- Disk copier
- File loader (COM, BIN)
- P2: Epson printer device driver supports full Atari ATASCII character set
- P3: Epson printer device driver supports double density printing
- Supports a computer modification, involving the installation of a second PIA
chip, that adds a built-in Centronics parallel printer interface (addressed
at $D6xx) to the Atari.
- Not available: PBI/ECI support, Self Test, International character set

Expander, by Syngery Concepts, 1987
- XL OS with added Executive Program for managing up to four Port B banked
memory RAM drives of up to 512KiB; boot from any RAM drive or any floppy
disk drive; built-in mini-DOS

Ultra Speed Plus! Operating System Package, CSS, 1988
- Module replaces OS ROM chip, with several lines soldered to points on
the motherboard as well. Three operating systems, switch-selectable:
- Standard Atari XL OS
- XL-Fix Plus
- 400/800 OS translator, with enhancements
- Mach-Ten binary file loader, with Mach Menu writer
- Ultra Speed Plus (US+)
- Universal support for high speed read/write with upgraded disk drives
including Super Archiver, Happy, US Doubler, Duplicator, Klone, Density
Doubler, and XF551
- RAM drive handler can emulate single or double density floppy disks,
supporting Port B banked memory in systems with 128KiB to 2MiB RAM.
- Can boot from RAM drive.
- Fastchip floating point routines
- Comprehensive memory test routine pinpoints defective RAM chips

Turbo-OS, by DataQue Software (Chuck Steinman), 1989
- Shipped with DataQue Software Turbo-816 65C816 board (both 600XL/800XL/65XE/
130XE and 1200XL versions)
- Compatible with software that uses the published, legal entry points into
the Atari XL OS and legal RAM locations
- Recommended to install both the Atari XL OS and the Turbo-OS ROMs, and a
toggle switch used to select which is active ("Dual Prom" Option).

TurBoss, by Integrated Logic Systems (ILS), 1990
- Enhances the screen display list speed in Graphics Mode 0
- Charles Marslett's high speed math routine (Fastchip)
- D.E.Mon real-time monitor built in
- Chip contains standard Atari XL OS as well, hardware switch selectable http://www.realdos.net/prodturboss.html

25K Bibomon, by Klaus Peters / Elektronik und Software, 1992
- Add-on board is marked: Supermon V1.1
- Single chip includes two operating systems: Old OS (Oldrunner?) and XL OS
- Board also includes Bibomon machine language monitor and optional
Bibo-Assembler
- Board includes socket for second XL/XE OS chip
- Firmware allows software control of combinations of OS (Old OS / XL OS /
Optional OS), with choices of international character set, Bibomon with
Bibomon DOS, Bibo-Assembler, and internal BASIC enabled
- Universal Speedy 1050 high speed support

APE Warp+ OS, by Atarimax (Steven J. Tucker), 1996
- Universal high speed SIO (3x), US Doubler emulation, other enhancements
- Shipped 1996-2005 as part of APE Warp+ Quad OS Upgrade Module, containing
APE Warp+ OS, standard XL OS, a public domain Atari 800 compatible OS,
and standard XL OS with Reverse BASIC
- Includes chip and 2 toggle switches
- Beginning 2005 shipped as part of APE Warp+ 32-in-1 OS Upgrade Module
- Module replaces OS ROM chip, with 3 other connections necessary
- OS Selection Menu in ROM

QMEG+OS 4.04 (c)'97 S.Dorndorf (1997)
- "Quarter-Mega Plus Operating System"
- For computers with 192KiB of Port B banked memory (256KiB total system RAM)
- Explicitly supported: Compy-Shop, Megaram, Buchholz, ABBUC,
Atari Magazin, Klan Atari, Newell
- When used in 64KiB or 128KiB computers RAM drives are not available
- Three RAM drive configurations supported:
1) Two RAM drives of 90KiB each (emulated SS/SD floppy disk drives)
2) One RAM drive of 128KiB (emulated SS/ED floppy disk drive),
one RAM drive of 64KiB (optionally compatible with DOS 2.5 RAM drive)
3) One RAM drive of 180KiB (emulated SS/DD floppy disk drive)
- High speed support: US Doubler/UltraSpeed, 1050 Turbo/Turbodrive, XF551
- Drive types automatically detected
- Full support for large Bibo-DOS, Turbo-DOS, and MYDOS floppy disks, and
MYDOS subdirectories
- Machine Language Monitor (MLM) with disassembler
- Disk copier
- File loader (COM, BIN, BAS, CAS)
- Boot from any drive
- CAS simulator (read only; no boot cassettes) replaces full C: device handler - Not available: Self Test, International character set, standard C: handler

MyBIOS ROM versions, by Sijmen Schouten (Mr. Atari), 2002-
- ROM versions are a complete replacement OS for the computer
- "The most compatible Atari XL/XE + 400/800 Operating system known"
- For all types of MyIDE interface
- 'E' version for external MyIDE; 'I' version for internal MyIDE http://www.mr-atari.com/myidehome.htm

65C816 XL OS (DracOS), by Konrad M. Kokoszkiewicz, 2004-
Top project goals:
- Make possible to use the 65C816 native mode on Atari XL/XE computers without
problems and with interrupts enabled.
- Make the memory mapped at extra addresses ($010000-$FFFFFF) accessible and
usable for programs.
- Provide some more extra services related to the 65C816 such as new interrupt
vectors, basic memory management routines etc.
- Develop new system of entry points: current mechanism of making ROM calls is
difficult to use, when the code resides above the address $FFFF. http://drac030.krap.pl/en-specyfikacja.php

------------------------------

Subject: 7.1.3) What is the ATASCII (Atari ASCII) encoding standard?

ASCII is an acronym for the American Standard Code for Information
Interchange. Pronounced ask-ee, ASCII is a character and control code
encoding standard used by computers, telecommunications equipment, and other devices. There are 128 valid codes in ASCII, including 95 printable
characters (including the "space" character) and 33 control codes.

The 8-bit Atari computers use a modified version of ASCII called Atari ASCII, or ATASCII. The ATASCII character set, contained in Operating System (OS)
ROM, includes 256 printable characters. Each character is a matrix of 8 x 8 pixels.

The XL OS contains both the standard ATASCII character set (as found in the 400/800 OS) and an alternate International Character Set, where 29 ATASCII standard "graphics characters" are replaced primarily with characters with European accent marks.

ATASCII printable characters are a functional superset of ASCII, with a few exceptions: ATASCII lacks the left curly bracket, right curly bracket, tilde, and grave accent printable ASCII characters. The similarity between ATASCII and ASCII character coding facilitates exchange of text between the Atari and other computers or devices also using character encodings based on ASCII.

16 of the ATASCII character codes also have control code functions when processed by the E: Screen Editor device of the Atari OS. ATASCII control codes are quite different from ASCII control codes. The most important functional difference between ATASCII and other variations of ASCII is how a "newline" (line ending, end of line (EOL), line break) is coded. The Atari's ATASCII uniquely uses the single decimal character code 155 to indicate a newline. Thus, when exchanging text files between the Atari and other computing devices a "text conversion" is necessary in order for newlines to be recognized as expected both before and after transmission.

The Wikipedia article on ATASCII provides links to several ATASCII/ASCII character tables, and a list of the ATASCII control codes. https://en.wikipedia.org/wiki/ATASCII

------------------------------

Subject: 7.1.4) How is the Input/Output subsystem of the Atari OS organized?

Derived primarily from the Operating System User's Manual and De Re Atari.

The Input/Output (I/O) subsystem of the Atari Operating System (OS) comprises
a collection of software utilities/routines, offered at three different levels of abstraction (CIO, Device Handlers, SIO), that allow for user communication with local system and peripheral devices. Communications between adjacent levels of the I/O subsystem are carried via one of the three types of I/O system control blocks (IOCB, ZIOCB, DCB).

Presented in order from the highest level to the lowest level:

USER PROGRAM

INPUT/OUTPUT CONTROL BLOCK (IOCB)
Carries communications between a user program and Central I/O (CIO)
- 8 IOCBs (#0-#7) are provided by the OS.
- Each IOCB can be assigned to control any device/file.
- IOCB #0 is assigned by the OS to the E: Screen Editor at power-up and
system reset.
- Software programming environments may reserve other IOCBs for internal
use. For example, Atari BASIC uses IOCB #6 to interact with the S:
device when using graphics modes other than zero, and uses IOCB #7 for
I/O with the printer, disk drive, and cassette. (Patchett/Sherer,
Master Memory Map, http://www.atariarchives.org/mmm/iocbs.php)

CENTRAL I/O (CIO) utility/routine
Intended for user program access to system and peripheral devices. A device consists of one or more "files" where each file consists of a sequential collection of data bytes. Files are optionally organized into "records" which are delineated by the End Of Line character/byte ($9B). 8 basic functions provided by CIO: OPEN, CLOSE, GET CHARACTERS, PUT CHARACTERS, GET RECORD,
PUT RECORD, GET STATUS, Special (handler-specific)
Additional CIO features:
- Device independence
- Single entry point for all devices (and for all operations)
- Device-independent calling sequence
- Uniform rules for data transfers, regardless of actual device storage
block sizes
- Data access methods
- Byte-aligned. Any number of bytes can be read or written, and the
next operation will continue where the prior one left off.
- Record-aligned. A single record of bytes can be read or written, and
the next operation will continue at the beginning of the next record.
- Multiple device/file concurrency
- Up to 8 device/files can be accessed concurrently, each operating
independently of the others.
- Unified error handling
- Device expansion: while the OS supplies several device handlers in ROM,
CIO also supports the loading of additional CIO-compatible device
handlers into RAM.

ZERO-PAGE I/O CONTROL BLOCK (ZIOCB)
Carries communications between higher-level CIO and lower-level device handlers. There is a single ZIOCB only.

DEVICE HANDLERS
Resident full device handlers provided by the Atari OS:
- K: Keyboard Handler (read only)

[continued in next message]

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)