Operating System is a System Software
System software is a type of computer program that is designed to run a computer’s hardware and application programs. Operating System is the best example of system software. An operating system (OS) is system software that manages computer hardware and software resources and provides common services for computer programs. All computer programs, excluding firmware, require an operating system to function.
MS-DOS, the acronym for Microsoft Disk Operating System, was an operating system with a command-line interface used on personal computers.
Windows 10 is a personal computer operating system developed and released by Microsoft. Windows 10 interfaces include an updated Start menu which incorporates elements of Windows 7's traditional Start menu with the tiles of Windows 8.
Linux is a Unix-like computer operating system assembled under the model of free and open-source software development and distribution.
Android "Nougat" is the seventh major version of the Android operating system. Android is a mobile operating system developed by Google, designed primarily for touchscreen mobile devices such as smartphones and tablets.
iOS 10 is the tenth major and latest release of the iOS mobile operating system developed by Apple Inc.
Multiprogramming, Multiprocessing and Multithreading
A multiprogramming computer runs more than one program at a time (like running Word and Google Chrome running simultaneously). Multiprogramming is also the ability of an operating system to execute more than one program on a single processor machine. More than one task/program/job/process can reside into the main memory at one point of time.
In Multiprocessing computer uses more than one CPU(processor) at a time. Multiprocessing is the ability of an operating system to execute more than one process simultaneously on a multi-processor machine.
A thread of execution is the smallest sequence of programmed instructions that can be managed independently. Multithreading is the ability of an operating system to execute the different parts of a program called threads at the same time. Threads are the light weight processes which are an independent part of a process or program.