World Library  
Flag as Inappropriate
Email this Article

Optimized Systems Software

Optimized Systems Software
Software Company
Fate Merged
Predecessor Shepardson Microsystems
Successor ICD
Founded 1981 (1981)
Founder Bill Wilkinson and Mike Peters
Defunct January 1988 (1988-01)
Headquarters Cupertino, California[1]

Optimized Systems Software (OSS) was a small company producing operating systems and programming languages for the Atari 8-bit and Apple II computer families. OSS is most noted for authoring Atari's BASIC and Disk Operating System (DOS) products.


  • History 1
  • Atari 8-bit products 2
    • OS/A+ 2.1
    • DOS XL 2.2
    • BASIC A+ 2.3
    • BASIC XL 2.4
      • BASIC XL Toolkit 2.4.1
    • BASIC XE 2.5
    • Action! 2.6
      • Action! Toolkit 2.6.1
      • Action! Run Time Package 2.6.2
    • EASMD 2.7
    • MAC/65 2.8
      • MAC/65 Toolkit 2.8.1
    • BUG/65 2.9
    • C/65 2.10
    • The Writer's Tool 2.11
  • Other products 3
  • Sales 4
  • Sources 5
  • External links 6


Optimized Systems Software was formed in early 1981 by Bill Wilkinson and Mike Peters, who had purchased Atari BASIC, Atari DOS and the Atari Assembler Editor product from Shepardson Microsystems, Inc. (SMI) who had concluded that their BASIC and DOS products were not viable. The new company enhanced the products, renaming them OS/A+ (the Disk Operating System), BASIC A+ (a disk-based language), and EASMD (a powerful assembler / editor). OSS continued to work with Atari (who had previously contracted with SMI) on enhanced products, most of which never reached the market.

OSS debuted at the West Coast Computer Faire, March 1981. Their products released over the next several years became respected among Atari programmers, particularly the MAC/65 assembler, the Action! programming language, and BASIC XL.

In January 1988, ICD and OSS merged. In 1994, Fine Tooned Engineering obtained limited rights to ICD's 8-bit products.

Atari 8-bit products


Atari DOS 2.0S consisted of two portions, a memory-resident portion that facilitated access to disk files by programs, and a disk-resident portion providing menu-driven utilities to format, copy, delete, rename, and otherwise manipulate files on Atari's 810 disk drive. The menu system was too large to keep memory-resident, but the necessity to reload the menu system after every program was frustrating to many users.

  • OS/A+ 2.0, 2.1 was a disk-based replacement for the Atari DOS and the Apple II DOS. It replaced the menu-driven utilities with a compact command line approach similar to CP/M (and later, DOS). The command line was small enough to remain in memory with most applications, removing the need for the dreaded post-program reload. When first introduced at the West Coast Computer Faire, the program was named CP/A, but a lawyer from Digital Research (owners of CP/M) visited the booth and the name was changed. OSS couldn't have afforded even a court filing fee.
  • OS/A+ 4.1 OSS extended the successful OS/A+ product with additional capabilities for version 4, many of which were arguably ahead of their time. For example, the strict "8.3" naming scheme (eight alphanumeric characters with a three character extension) was replaced by "long" filenames, similar to the Microsoft DOS transition to VFAT in 1995.

However, unlike VFAT, OS/A+ 4.1 disks were not backward compatible with earlier systems; Atari DOS or OS/A+ 2.1 could not read disks formatted by OS/A+ 4.1, breaking backward compatibility. The memory footprint was larger as well, resulting in insufficient memory to run some popular applications.

As a result of these drawbacks, OS/A+ 4.1 did not achieve the market penetration as the earlier product.

OSS did reissue OS/A+ 4.1 for a brief period when they decided not to modify DOS XL for double-sided disk support.


DOS XL was designed to replace OS/A+. Included support for single and double-density disk drives. Utilized the command-prompt of OS/A+ but also included a menu program. Featured extensions that took advantage of unused memory space in Atari XL/XE computers and OSS Super-cartridges. Included support for Indus GT Synchromesh.

Written by Paul Laughton, Mark Rose, Bill Wilkinson and Mike Peters.

Due to lack of demand and Atari working on a new version of DOS, OSS decided to halt development of DOS XL 4 and reissue OS/A+ version 4.1.

Available on disk.


Atari BASIC had been designed to fit in a single 8k cartridge, with an optional second cartridge adding additional capability (the Atari 800 home computer featured two cartridge slots). However, the second cartridge was never produced.

Instead, OSS produced a disk-based product called BASIC A Plus (or BASIC A+), which was compatible with Atari BASIC but corrected several bugs and added quite a few features. Among the notable features were PRINT USING (for formatted output), trace and debug enhancements, direct DOS commands, and explicit support for the Atari computers' exceptional graphics hardware.

Because BASIC A+ had to be purchased, programs developed using its extended features could not be shared with people who did not own the interpreter.

Available on disk only.


Replaced BASIC A+. Fixed bugs and added even more commands and features.

Available in an OSS bank-selected cartridge.

BASIC XL Toolkit

This disk contained additional code and examples for use with the BASIC XL language. Included a runtime package for redistribution. No compiler was available.


Enhanced version of BASIC XL, contained additional functions and high-speed math routines. Because it required 64kB, it would only run on an XL/XE system.

Available in an OSS bank-selected cartridge and extension disk. No compiler or runtime was made available. The BASIC XL runtime could be used, but restricted to only XL functions.


A cartridge-based development system for a readable ALGOL-like language that compiles to efficient 6502 code. Action! combines a full-screen editor with a compiler that generates code directly to memory without involving disk access. The language found a niche for being over a hundred times faster than Atari BASIC,[2] but much easier to program in than assembly language. Compiled Action! programs require the cartridge to be present—because standard library functions are on the cartridge—unless the developer uses the Run Time Package (which was a separate purchase).

Action! Toolkit

Originally called the Action! Programmer's Aid Disk (PAD), this disk contains additional code and examples for use with the Action! language.

Action! Run Time Package

Allows Action! programs to be redistributed to Atari users without the Action! cartridge.


EASMD (Edit/ASseMble/Debug) was the first editor/assembler from OSS. Enhanced from the original Atari Assembler Editor. Superseded by MAC/65.

Available 1981 on disk only.


MAC/65 was a 6502 editor/assembler. A replacement for EASMD, MAC/65 featured macros and conditional assembly.

Written by Steven D. Lawrow.

Available 1982 on disk, 1983 on an OSS bank-selected cartridge.

MAC/65 Toolkit

This disk contained additional code and examples for use with the MAC/65 editor/assembler.

Available on disk, required 48K of memory.


A machine language debugger produced by Optimized Systems Software. Initially included with MAC/65, it was later added to DOS XL.


C programming language for the Atari. A subset of C, C/65 only generated assembly source code. An assembly compiler (like MAC/65) was needed to generate an executable file.

Marketed, not produced by OSS.

The Writer's Tool

A word processing application from OSS. Required 48K of memory.

Available in an OSS bank-selected cartridge and a double-sided disk (Master disk on one side, dictionary disk on the other side).

Other products

OSS was involved with other projects, such as a modified BASIC and DOS for the Atari 7800 game system, Personal Pascal and Personal Prolog for the Atari ST, and others.


According to Bill Wilkinson, OSS sold about 12,000 copies of Basic XL before the ICD merger. Basic XL outsold Action! by about 2.5 or 3 to 1. MAC/65 outsold Action! by about 1.5 to 1. Basic XE sold poorly, a money-loser. Personal Pascal sold over 10,000 copies.


  1. ^ "Inside Atari DOS - Introduction". 
  2. ^ Moriarty, Brian (1984). "A New Langue for the Atari!". ANALOG Computing. 
  • Wilkinson, Bill (1983). The Atari BASIC Source Book. Compute! Books. ISBN 0-942386-15-9.
  • A User's Guide and Reference Manual for DOS XL 2.30, 1983
  • OSS Newsletter - Spring 1984
  • OSS Newsletter - October 1984

External links

  • Dan's tribute to OSS — A site dedicated to the products produced for Atari 8-bit computers by Optimized Systems Software.
  • The Atari 400/800 and OSS
  • Antic Vol. 4, No. 9 - Jan 1986 Basic XE from O.S.S. (Product Review)
  • Antic Vol. 3, No. 11 - Mar 1985 The Writer's Tool (Product Review)
  • ICD, Incorporated former OSS software distributor
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.