Three extensions are considered in this chapter. Two are additions made to the original X Window system. One of those additions extents the Pixmap concept to enable use of more than two colours in a pattern which can be mapped onto a window. The other is the introduction of fonts which are scalable, i.e. can be changed to any size required. Both are now a part of standard X Window system. The remainder is an extension to the manner of executing a X Window program.