X; X-1; X11R4; X11R5; X11R6; X.12; X2; X.208; X.209; X.21; X.214; X.215; X.216; X.217; X.219; X.224; X.225; X.226; X.227; X.229; X.25; X.28; X.29; X.3; X3J16; X3T10; X.400; X.409; X.500; X.680; X.75; x86; x86 processor socket; XA; Xaw; Xbase; xbeeb; xbm; XC; X client; X Consortium; Xcoral; xdbx; X-Designer; X.desktop; XDL; XDR; XDS 940; xDSL; Xemacs; XENIX; Xeon; XEROX Corporation; Xerox Data Systems Model 940; XEROX Network Services; XEROX PARC; Xerox Star; XFree86 Project, Inc.; Xfun; XGA; XGA-2; XHTML; Xi; XIE; Xilinx, Inc.; Xilinx Netlist Format; X Image Extension; Xlib; xlisp; xls; XML; XMM; XMODEM; XMODEM-1K; xmosaic; XMS; XNF; xnf2ver; XNS; XOFF; XON; XON/XOFF; Xopen; X/Open; X/open Portability Guide; X/Open System Interface; xor; XPC; XperCASE; XPG; XPG3; XPL; xpm; XPOP; Xpress Transport Protocol; X protocol; xref; XRemote; XRN; XSB; XScheme; x-scm; X server; XSI; XSL; XSLT; XT; Xt; XT bus architecture; xterm; X terminal; XTI; XTP; XTP Forum; XTRAN; XUI; Xv++; XVGA; XView; XVT; X-Windows; X Window System; XWIP; xxgdb; XXX; Xy-pic; xyzzy;