UNIX 
The foundations of Mac OS X: an explanation.
UNIX, the robust foundation of Mac OS X is an operating system that 's popular among large company- and university computers, called mainframes.
Bell Laboratories developed the first Unix in 1996. 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 X on. By the way: the popular Linux is also a Unix variety.
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?
In UNIX, 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 maces with the Graphical User Interface was introduced in 1984. It started a revolution. In those days, computers were commanded by typing in text commands. Before you could use a computer, you had to learn those commands by heart. But Apple introduced a little box that worked with a mouse, talked and showed pictures and icons.
In the years after the introduction, the Mac OS expanded, until it nearly grew out of its jacket. Apple decided that it was time to build a new system, not to build from scratch, but based on the ancient but bullet-proof UNIX.
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.
TIP
Unix commands in Mac OS X
Using text commands is not something the newbie Mac user interests, but they can be useful. Here are some examples:
To stop all programs at once and shut down your Mac:
sudo halt
Open the cd tray:
drutil tray open
(yes, Unix commands use spaces in between!)
Ping to an IP address (in this case my modem):
Other useful Unix commands
To check and repair the file system
Boot in Single User mode: push Command S while booting up.
Instead of the blue screen you'll see a black screen with the boot processes in Unix language:
"Copyright: "The Regents of the University of Berkeley, California" tells us that we really deal with BSD-Unix. :-)
To repair permissions we type
/sbin/fsck -fy
Then hit the return key once.
You'll screen 'll show you something like this:
localhost / # /sbin/fsck -f
** /dev/rdisk0s3
** Root file system
** Checking HFS Plus Volume.
** Checking Extents Overflow file.
** Checking Catalog file.
** Checking multi-linked files.
** Checking Catalog hierarchy.
** Checking volume bitmap.
** Checking volume information.
** The volume MacintoshHD appears to be OK.
Repeat the fsck command until it gives an 'OK'.
Then use the command 'reboot'. The Mac will restart now.
Telnet / SSH
You can use Terminal to access a server through Telnet protocol or SecureShell (SSH).
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.
CUPS
An alternative way to install printers is through CUPS. This Common Unix Printer Service can be accessed by typing the following address into your browser:
http://localhost:631 .
Select 'Printers'. Here you can see the printers that are already installed. You can use this page to manage them, print a testpage, etcetera:
To add a new printer, select the 'Administration' tab and choose 'Add printer':
Type a name for your new printer. (you can leave the other fields empty):
Now choose how your printer will be connected to your Mac:
Here our printer is connected to a router. That router has IP address 192.168.2.1.
In this case we use LPD/LPR Host or Printer:
Now type the printer's address: lpd://192.168.2.1/LPT1:
Now we choose the right driver:
Note that you can also uploade a PPD file
And then we select the right printer:
And the printer has been added.
Note that this specific configuration is suited for the KPN modem "Experiabox" in the Netherlands. It might not work for you like this, so you might need to experiment to get your own settings right.
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, but the common user can also use free-ware programs like Onyx, Macaroni, Cocktail (shareware) or Yasu.
Make sure that the system utiltiy you use is suitable for Mac OS 10.5 Leopard.
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