Optimized Systems Software

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Optimized Systems Software
Software Company
PredecessorShepardson Microsystems
Founded1981; 38 years ago (1981)
FoundersBill Wilkinson
Mike Peters
DefunctJanuary 1988; 31 years ago (1988-01)
Cupertino, California[1]

Optimized Systems Software (OSS) was a company that produced disk operating systems, programming languages, and applications primarily for the Atari 8-bit family of home computers, but some products were also sold for the Apple II.[2] OSS was best known for their enhanced versions of Atari BASIC and the MAC/65 assembler (both of which are much faster than Atari's products) and the Action! programming language.

OSS transitioned to other platforms with Personal Pascal for the Atari ST[3] and Personal Prolog for Macintosh (which was also advertised for the Atari ST, but may not have been released). OSS was not as significant in those markets.


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.

Disk Operating Systems[edit]


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, MS-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[edit]

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 supercartridges. Included support for Indus GT Synchromesh. 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.[citation needed]


BASIC A+[edit]

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.

BASIC XL[edit]

A bank-selected cartridge version of the language that replaced BASIC A+. It fixed bugs and added even more commands and features. The BASIC XL Toolkit contains additional code and examples for use with the BASIC XL language. Included a runtime package for redistribution. No compiler was available.

Antic in 1984 stated that "BASIC XL is the fastest and most powerful version of BASIC available for Atari computers", with "exceptional" documentation. The magazine concluded that "This is the language that should be built into Atari computers. Is anyone at Atari listening?"[4]

BASIC XE[edit]

An enhanced version of the BASIC XL bank-selected cartridge,with additional functions and high-speed math routines. Because it required 64KB, it would only run on an XL/XE system. No compiler or runtime was made available. The BASIC XL runtime could be used, but restricted to only XL functions.



EASMD (Edit/ASseMble/Debug) is the first editor/assembler from OSS. Based on the original Atari Assembler Editor, it was released in 1981 on disk. It was superseded by MAC/65.


MAC/65 is 6502 editor/assembler originally released on disk in 1982, then on a bank-switched "supercartridge" in 1983 which included an integrated debugger (DDT). Like Atari BASIC, MAC/65 used line-numbered source code and tokenized each line as it was entered. It was significantly faster than Atari's assemblers. The MAC/65 Toolkit disk contains additional code and examples.


A machine language debugger. It was initially included with MAC/65, but the cartridge-based version of the assembler added its own debugger, DDT. BUG/65 was later added to DOS XL.

Other languages[edit]


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,[5] 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. The separately available Action! Run-Time Package overcomes this limitation and allows distribution of Action!-compiled projects.

The Action! Toolkit (originally called the Programmer's Aid Disk, or PAD) contains additional code and examples for use with the Action! language.


A compiler developed by LightSpeed Software for a subset of the C programming language.[6] C/65 outputs assembly source code. An assembler like MAC/65 is needed to create an executable file.

Tiny C[edit]

Tiny C, stylized as tiny-c, is an interpreter for a subset of the C programming language developed by Tiny C Associates.[2]

Personal Pascal[edit]

A one-pass, machine code generating compiler for the Pascal language developed by J. Lohse for the Atari ST and released by OSS in 1987.[3] It came with a 500+ page manual.


The Writer's Tool[edit]

A word processing application available in a bank-selected cartridge and a double-sided disk (master disk on one side, dictionary disk on the other side).[7] It was developed by Madison Micro and published by OSS in 1984.[8] According to Bill Wilkinson, OSS was already building a word processor, but stopped when The Writer's Tool was submitted.[9]


A speed reading tutor the Atari 8-bit and Apple II computers.[2]


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.[citation needed]


  1. ^ "Inside Atari DOS - Introduction".
  2. ^ a b c "The First and Finest (OSS magazine ad)". Atari Mania.
  3. ^ a b "Personal Pascal for the Atari ST Manual". archive.org.
  4. ^ White, Jerry (March 1984). "Product Reviews". Antic.
  5. ^ Moriarty, Brian (1984). "A New Langue for the Atari!". ANALOG Computing.
  6. ^ "C/65". Atari Mania.
  7. ^ Rainbow, Tom (March 1985). "8-bit Product Reviews: Writer's Tool". Antic. 3 (11).
  8. ^ The Writer's Tool Manual (PDF). Optimized Systems Software, Inc. 1984.
  9. ^ "Interview 7: Bill Wilkinson". ANTIC The Atari 8-bit Podcast.
  • 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[edit]