Macintosh computers come pre-loaded with OS X. Many corporate servers use the Linux or UNIX operating systems. The operating system (OS) is the first thing loaded onto the computer -- without the operating system, a computer is useless.

Traditionally, a vade mecum (pronounced ‘‘VAHdee MAYkem’’) is a laboratory manual
that guides the student step by step  through complex procedures. Operating systems are
complex mixtures of policy and mechanism, of algorithm and heuristic, and of theoretical
goals and practical experience. This vade mecum tries to unify these diverse points of
view and guide the novice step by step through the complexities of the subject. As a text,
this book is intended for a first course in operating systems at the undergraduate level.

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# 1. What is an operating system?

* 1.1 Key concepts
o 1.1.1 Hierarchies and black boxes
o 1.1.2 Resources and sharing
o 1.1.3 Communication, protocols, data types
o 1.1.4 System overhead
o 1.1.5 Caching
* 1.2 Hardware
o 1.2.1 The CPU
o 1.2.2 Memory
o 1.2.3 Devices

o 1.2.4 Interrupts, traps, exceptions
* 1.3 Software
o 1.3.1 Resource management
o 1.3.2 Spooling
o 1.3.3 System calls
o 1.3.4 Basic command language
o 1.3.5 Filesystem

Mac OS X is a unique operating system in that it represents a rather successful coming together of paradigms, ideologies, and technologies that have usually resisted each other in the past. It is a result of the trials and tribulations of Apple and NeXT, as well as their user and developer communities. Mac OS X is perhaps one of the best examples of how a capable system can result through the direct or indirect efforts of corporations, academic and research communities, the Open Source and Free Software movements, and even individuals.