XNF xnf2ver XNS XOFF XON XON/XOFF Xopen xor XPC XperCASE XPG XPG3 XPL xpm XPOP
| Xpress Transport Protocol xref XRemote XRN XSB XScheme XSI XSL XSLT XT Xt XT bus architecture xterm XTI XTP
| XTP Forum XTRAN XUI XUL Xv++ XVGA XView XVT XWIP xxgdb XXX Xy-pic xyzzy
|