The Operating System (OS) is a complex piece of system software found on general-purpose computer systems.

Common operating systems include Android, iOS, macOS, and Windows.

The OS has six main jobs:

• Processor management
  Each CPU core can only process one instruction at a time, so if you have multiple applications running, it's the OS's job to tell the CPU which application's instructions to process. Operating Systems schedule different tasks, using a priority system to make some applications' tasks wait in a queue.
• Memory management
  The OS manages which bits of RAM each application is allowed to use. This makes sure that applications don't interfere with or overwrite each other's data. When applications are closed, the OS removes their data from RAM.
• Input/Output device management
  I/O devices (like keyboards, microphones, or speakers), also called "peripherals", allow computers to take inputs and give outputs. Operating Systems use device drivers to communicate with I/O devices.
• Application management
  The OS has to install an application onto your computer when you download it. It also communicates with an Applications Program Interface (API) to allow the application to interact with your computer. The OS also provides an interface through which applications can be accessed.
• Disk management
  Your files aren't stored in folders in your computer. They're all stored in the same place on your hard drive. The OS has to keep track of where each file is stored on your hard drive, and also your folder structure.
• Security management
  The OS manages login details for different users on your computer, as well as user access permissions. It also encrypts files on the hard drive to keep them secure.

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Why don't embedded systems have an OS?

Their memory is too small to store an OS, and they don't need one because none of the six tasks above apply to an embedded system.

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