Definition of "operating system" []

• Software designed to control the hardware of a specific data-processing system in order to allow users and application programs to make use of it. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "The first version to run under the ProDOS operating system was called Apple Writer 2.0."
• "Notice the use of os. sep variable - this gives the directory separator according to your operating system i.e. it will be"
• "Known as a “water-based mechanism,” this was the standard operating system behind all Egyptian moving-wall traps."