There are approximately 3.1 million active registered nurses in the United States. There, a registered nurse is a clinician who has completed at least an associate degree in nursing or a hospital-based diploma program.
An operating system normally also provides the default user interface for the system. The standard look of Windows 98 includes the Start button, the task bar, etc. The Mac OS provides a completely different look and feel for Macintosh computers. Linux is as much a phenomenon as it is an operating system. To understand why Linux has become so popular, it is helpful to know a little bit about its history. The first version of UNIX was originally developed several decades ago and was used primarily as a research operating system in universities.
Gartner reported on 23 December 2008, that Linux on System z was used on approximately 28% of the customer z base and that they expected this to increase to over 50% in the following five years. Of Linux on System z, Red Hat and Novell compete to sell RHEL and SLES respectively. Prior to 2006, Novell claimed a market share of 85% or more.