A B C D E F G H I J
K L M N O P Q R S T
U V W X Y Z 0...9

XA
XAPIA
XBASE
X_CONSORTIUM
XENIX
XGA
XMP
XMS
XNS
X/OPEN
XPG
XSI
X_TERMINAL
XTI
XTP
X-WINDOWS
X_WINDOW_SYSTEM
X.21
X.25
X.200
X.400
X.500
X.700
X.800