Update Sequence Number (USN)
Provides a persistent log of all of the changes made
to the files on the system. As users add, delete, and
modify files and directories, the Windows NT File
System (NTFS) makes an entry in the USN. Each
volume has a separate USN. The main use of the
USN for administrators is to check the changes made
to one or more files. Using the USN is more efficient
than relying on time stamps and the administrator
receives more information as well.
Upper Memory Block (UMB)
The area of memory between 640 KB and the 1 MB
boundary. IBM originally set aside this area of
memory for device ROMs and special device
memory areas. Various memory managers,
including the one supplied with Windows, let you
load applications and device drivers in this area to
free more memory in the lower 640 KB area.
URI
See Uniform Resource Identifier
URL
See Uniform Resource Locator
User Account Control (UAC)
A Windows security feature that increases security
by reducing the chance that an application can perform
any act on the user??™s behalf, without the user??™s
knowledge. This feature first appeared as part of
Windows Vista. The operating system displays a
dialog box asking permission to perform the
required task.
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