Unix is an operating system. An operating system takes instructions
from the user for starting applications and manages the computer
resources, including memory, processor, and the file system. Unix,
Macintosh Windows and Microsoft Windows are operating systems. Unix
(Linux is a version of Unix) and the older DOS are command-line based,
whereas Windows are point and click. A command-line operating system
gives the user far greater control, so it is the superior tool for
computational science and engineering, but it requires some practice
to learn. In this course we try to make the learning curve gentle.
The keyboard is our main user interface. So just a word about
entering commands: Remember, to direct keyboard entries to a window,
you must click on the terminal window before typing into it, unless you
have enabled the ``Auto Raise'' feature. You begin by typing on a
line. To complete a command, you must hit the Enter key. Once
you hit Enter, the command is issued. Before that, you can edit
it. If you make a mistake, use the backspace key to rub out the
previous character(s), or use Ctrl-u to erase the entire line.
Ctrl-u means holding down the Ctrl key while hitting the
u key. Try this a few times with the pwd command.