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