By Bob LeVitus

The operating system (that is, the OS in OS X) is what makes a Mac a Mac. Without it, your Mac is a pile of silicon and circuits — no smarter than a toaster.

“So what does an operating system do?” you ask. Good question. The short answer is that an OS controls the basic and most important functions of your computer. In the case of OS X and your Mac, the operating system

  • Manages memory

  • Controls how windows, icons, and menus work

  • Keeps track of files

  • Manages networking and security

  • Does housekeeping (No kidding!)

Other forms of software, such as word processors and web browsers, rely on the OS to create and maintain the environment in which they work their magic. When you create a memo, for example, the word processor provides the tools for you to type and format the information and save it in a file. In the background, the OS is the muscle for the word processor, performing crucial functions such as the following:

  • Providing the mechanism for drawing and moving the onscreen window in which you write the memo

  • Keeping track of the file when you save it

  • Helping the word processor create drop-down menus and dialogs for you to interact with

  • Communicating with other programs

  • And much, much more (stuff that only geeks could care about)

One last thing: OS X El Capitan comes with more than 50 applications.