Apple SOS

Infobox OS
name = Apple SOS
logo =


caption =
website =
developer = Apple Computer, Inc.
family = SOS
source_model = Closed source
latest_release_version = 1.3
latest_release_date = 1982
marketing_target =
language =
kernel_type = Monolithic kernel
ui = Full screen text mode
license = Apple Software License Agreement
working_state = Historic
supported_platforms = Apple ///
updatemodel = Manual
package_manager =
Apple Computer, Inc. gave the acronym SOS (pronEng|ˈsɔːs) [cite web
url = http://www.apple3.org/Manuals/Apple%20III%20SOS%20Reference%20Manual%20Volume%201%20-%20How%20SOS%20Works.PDF
title = Apple III SOS Reference Manual, Volume 1: How SOS Works
first = Reed
last = Don
publisher = Apple Computer, Inc.
format = PDF
year = 1982
accessdate = 2007-12-08
quote = This manual describes SOS (pronounced "sauce") the Sophisticated Operating System of the Apple III.] the meaning Sophisticated Operating System [cite web
url = http://apple2history.org/history/ah15.html#SOS
title = SOS/PRODOS
work = Apple II History
accessdate = 2008-09-26
quote = The operating system designed for the Apple III computer was called "SOS". This title arose from the Apple III's code name, "Sara", which itself came from the name of engineer Wendell Sanders' daughter.] when the operating system was released in 1980. SOS made the resources of the Apple III available in the form of a menu-driven utility program as well as a programming API.

The Apple /// 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:
# Device handling commands - Copy, rename, format, verify volumes (drives); list devices; set time and date
# File handling commands - List, copy, delete, rename files; create subdirectories; set file write protection; set prefix (current working directory)
# System Configuration Program (SCP) - Configure device drivers.cite web
url = http://www.1000bit.it/support/manuali/apple/a3/Apple%20III%20Owner%27s%20Guide.PDF
title = Apple III Owner's Guide
publisher = Apple Computer, Inc.
format = PDF
year = 1982
accessdate = 2008-09-28]

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:
# 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
# Device Calls - get status, device number, information of a device; send device control data
# Memory Calls - Request, find, change, release memory segment; get segment information; set segment number
# 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. [cite web
url = http://www.1000bit.it/support/manuali/apple/a3sosrm.pdf
title = Apple III SOS Reference Manual, Volume 1: How SOS Works
publisher = Apple Computer, Inc.
format = PDF
year = 1982
accessdate = 2008-09-28]

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.cite magazine
title = John Jeppson's Guided Tour of Highway III
first = John
last = Jeppson
publisher = Softalk Magazine
month = May | year = 1983
page = 100-112]

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 (£2,420).cite web
url = http://www.wap.org/a3/a3library/a3faq.html
title = The Apple /// FAQ File (V5.1)
first = David
last = Ottalini
publisher = Washington Apple Pi Users Group
month = August | year = 2005
page = Section 1
accessdate = 2007-12-08] In addition, SOS was not friendly to software developers even though having a variety of software available was crucial for the computer's success; developer David Fradin noted that "SOS was not really usable for programming until early '83."

References

External links

* [http://www.wap.org/a3/ Washington Apple Pi - Apple /// Resources]
* [http://www.wap.org/a3/a3library/a3faq.html The Apple /// FAQ File V5.1] — discusses Apple III and SOS history as well as basic information about the system