Operating System and data encryption cryptograpghy modules.

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The Mac uses only plug-in memory modules, its operating system automatically recognizes all the memory present, and all Mac software can share it.

WSJ: Here's How to Survive Shopping for a PC

The Microsoft Windows 8 operating system will bring the Trusted Platform Modules (TPMs, the basis of storage device-based encryption security as well as additional security features) to wider use for enterprise applications.

FORBES: Creating Security from the Inside Out