Apple SOS - Technical Details

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 application programming interface 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 devices 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.

Read more about this topic:  Apple SOS

Famous quotes containing the words technical and/or details:

    “The axioms of physics translate the laws of ethics. Thus, “the whole is greater than its part;” “reaction is equal to action;” “the smallest weight may be made to lift the greatest, the difference of weight being compensated by time;” and many the like propositions, which have an ethical as well as physical sense. These propositions have a much more extensive and universal sense when applied to human life, than when confined to technical use.”
    —Ralph Waldo Emerson (1803–1882)

    “Patience is a most necessary qualification for business; many a man would rather you heard his story than granted his request. One must seem to hear the unreasonable demands of the petulant, unmoved, and the tedious details of the dull, untired. That is the least price that a man must pay for a high station.”
    —Philip Dormer Stanhope, 4th Earl Chesterfield (1694–1773)