Apple SOS

Apple SOS

Developer	Apple Computer, Inc.
OS family	SOS
Working state	Historic
Source model	Closed source
Latest release	1.3 / 1982
Update method	Manual
Platforms	Apple III
Kernel type	Monolithic kernel
Default user interface	Full screen text mode
License	Apple Software License Agreement

The Sophisticated Operating System, or SOS (Template:PronEng), is the primary operating system developed for the Apple III computer. The system was developed by Apple Computer, Inc. and released in 1980. SOS makes the resources of the Apple III available in the form of a menu-driven utility program as well as a programming API.

The Apple III System Utilities program shipped with each Apple III computer. It provided what today would be called the end user "experience" of the operating system if the user were running it instead of an application program. The System Utilities program was menu-driven and performed tasks in three categories:

1. Device handling commands - Copy, rename, format, verify volumes (drives); list devices; set time and date
2. File handling commands - List, copy, delete, rename files; create subdirectories; set file write protection; set prefix (current working directory)
3. System Configuration Program (SCP) - Configure device drivers.

Technical details

SOS was a single-tasking operating system. A single program is loaded at boot time, called the interpreter. Once running, the interpreter could then use the SOS API to make requests of the system. The SOS API was divided into four main areas:

1. File Calls - create, destroy, rename, open, close, read, write files; set, get prefix (current working directory); set, get file information; get volume information; set, set mark, EOF, and level of files
2. Device Calls - get status, device number, information of a device; send device control data
3. Memory Calls - Request, find, change, release memory segment; get segment information; set segment number
4. Utility Calls - get, set fence (event threshold); get, set time; get analog (joystick) data; terminate.

SOS had two types of devices it communicated with via their device drivers: character and block devices. Examples of SOS character devices are keyboards and serial ports. Disk drives are typical block devices. Block devices could read or write one or more 512-byte blocks at a time; character devices could read or write single characters at a time.

Boot sequence

When powered on, the Apple III ran through system diagnostics, then read block number one (zero-indexed) from the built-in diskette drive into memory and executed it. SOS-formatted diskettes placed a loader program in block one. That loader program searched the diskette directory for a file named SOS.KERNEL, the kernel and API of the operating system. The SOS loader program loaded and executed the SOS.KERNEL file, which in turn searched for and loaded a file named SOS.INTERP (the interpreter, or program, to run) and SOS.DRIVER, the set of device drivers to use. Once all files were loaded, control was passed to the SOS.INTERP program.

History and conjecture

In spite of SOS's advantages, it wasn't natively backward compatible with DOS 3.2 and DOS 3.3, which most Apple II software used at the time—though the Apple III itself was designed to be mostly backward-compatible with the Apple II Plus in hardware, users had to boot Apple DOS from a separate disk to use Apple II series software, losing the advantages of SOS. Many average computer users also weren't ready in 1980 for an operating system with the capabilities and flexible configuration options that SOS offered, especially combined with the Apple III's bad reputation due to poor engineering and its high retail price near $4,000

The Apple III's problems occurred in the year it shipped, 1980, under the direction of Apple's Vice President of Product—Steve Jobs. Unknown at the time, the chips on the motherboard worked themselves loose when the computer was shipped. This was fixed with the humorous act of dropping the computer from one foot up to reseat the chips. That initial problem coupled with a not yet complete operating system and development tools hurt the first years of the Apple III's life. In addition, SOS was not friendly to software developers even though having a variety of software available was crucial for the computer's success; Apple III Business Unit Manager David Fradin noted that "SOS was not really usable for programming until early '83" at which time a large number of sophisticated applications came to market including Great Plains accounting, Super Visicalc, Pagemaker, Quark Word Processing and Three Easy Pieces, the predecessor of Microsoft Works. Most of these companies and/or products continue to thrive in 2009, 25 years later. David Fradin's team successfully transfered 500 developers to Guy Kawasaki, who at the time was the Macintosh evangelist.

The Apple III was a business computer. Its OS, for example, with a UNIX-like structure, was the first PC to use the concept of "directories" was very difficult for users to understand. It also supported the first hard disk drive for a personal computer, using the Seagate ST-501 5 MB drive that sold for $3,600.

While frequently derided as a failure, the Apple III was hardly that. At the end of July 1983 Apple had sold over 50,000, making it the third largest installed base of PCs and mini-computers. Only the Apple II and the DEC PDP 11 had out-shipped it. When David Fradin's Apple III Independent Business Unit took over in August 1983, the Apple III no longer had to compete for resources with the Apple II and the soon-to-ship Lisa. The Apple III was a business computer and was used by businesses worldwide. While shipments were just 5–10% of Apple IIs, Apple profited six times that of the sale of an Apple II. But Del Yokam, Apple's VP of Manufacturing, was bothered by the low volume and Steve Jobs felt he had to kill his former creation to make way for his new baby—the Macintosh.

So David Fradin, the new Apple III Product Manager, was asked by John Scully what Apple should do about the Apple III after the company's Executive Committee killed the product line and then found out they would have to take a $20 million inventory write-off. David Fradin told Scully that if he could be given the authority to engineer, market and sell the Apple III to go along with the responsibility, he could sell them. With co-Personal Computer Systems Division General Manager Paul Dali clearing the way, Fradin gathered a core team of 12 and the imputs from 60 others who prepared an 80-page business plan and made recommendation to the Executive Committee. Recommendations covered all aspects of engineering, marketing and sales through 1,800 dealers worldwide. They also included an analysis against Apple's values.

A key part of the meeting occurred when Senior Vice President Floyd Kvamme asked "if we pick the option of killing the Apple III vs. the option of letting the market decide, Fradin what would you say differently if a dealer would call you about each option". Fradin responded "if you let the market decided, I'll tell the dealer that the continuation of the Apple III depends upon people buying them. If you kill it, which is against Apple's core values, I'll give the dealer your phone number."

Ten days later, Ken Zerbe, Apple's CFO, called David Fradin to recruit him to head up what he had recommended—an Independent Business Unit for the Apple III. That team of 17 people went on over the next 11 months and sold 25,000 Apple IIIs and III+'s , eliminated the inventory exposure and when product ran out they shut it down on the day the Apple IIc was introduced. Wall Street hardly noticed. Apple's stock price remained constant and the full transition to the Macintosh had begun.

External links

• Washington Apple Pi - Apple /// Resources
• The Apple /// FAQ File V5.1 — discusses Apple III and SOS history as well as basic information about the system
• apple3.org - Apple /// Articles, Public Domain Software