The engine under the hood

UNIX: the robust foundation of Mac OS
UNIX is an operating system that 's popular among large company- and university computers, called mainframes.
Bell Laboratories developed the first UNIX in 1969. In those days, computer memory was very expensive and computers were as large as an average living room. Because of the huge costs, it was necessary to use very small programs that needed little Random Access Memory. Unix contains a lot of very small programs. A characterization of small programs is that they contain less programming errors than large, heavy programs. And, if one crashes, it doesn't affect another, which is beneficial for system stability.
Unix is a very powerful operating system, which made 'multitasking' (it handles several instructions at a time) and 'multi-user' (multiple users working at one system at a time) possible. Since 1969 Unix has undergone many improvements and can call itself the most reliable operation system on the planet.
There are several varieties like HP-UX, SGI, Sun Solaris, IRIX and at the University of Berkeley developed version Free BSD. And this is the operation system Apple based Mac OS on.
By the way: the popular Linux is also a Unix variety!

Command line or GUI
Unix is commanded by text commands of two or more letters, or in this case by a Graphical User Interface. Apple called this interface 'Aqua'. The GUI makes sure you do not have to remember any text based commands and gave Unix the user friendliness of the Apple Macintosh.

Why Unix?
UNIX is stable. It's system software rarely crashes. But when it does, it cannot take the whole system down. The old Mac OS, (today called 'Classic') was much more sensitive. A crash once a week used to be quite normal, however mostly caused by Microsoft (!) software. An Apple system without MS software crashed a lot less.

The Macs with the Graphical User Interface was introduced in 1984. It started a revolution.
In those days, computers were commanded by typing in text commands (MS-DOS). Before you could use a computer, you had to learn those commands by heart.
But then, Apple introduced a little box that worked with a mouse, talked and showed pictures and icons.

In the years after the introduction, the MacOS expanded, until it nearly grew out of its jacket. Apple decided that it was time to build a new system. Not one to build from scratch, but based on the ancient, but bullet-proof UNIX.

Typing instead of mousing

So, for who likes text interfaces, you can command the Mac with text-commands now in the Terminal program:

A simple command you can try is 'ls'. It shows the contents of your home folder:

Short lists of UNIX commands are to find on thousands of UNIX and Linux websites.

Log files
Unix monitors the events within its system very carefully. You can look at these 'log files' with the help of the 'Console' program.

Another advantage of Unix: system maintenance by the system itself.
If your Mac is working 24/7 and doesn't fall asleep (except display) than the System can maintain it.
In the OS there are a lot of non-visible files, which can take a lot of space on your hard disc, slowing it down. These files are removed daily, weekly or monthly, or at reboot.
Off course the die-hard users out there can do this manually from the Terminal.

Disclaimer: MacMiep is independent. This means she writes what she wants, based on 25+ years of Mac-experience. She doesn't get paid for stories (positive or negative) on this website.