In order to get a foundation from which to build a better understanding of Xt, it is important to discuss a few concepts prior to diving in. This chapter is intended to get everyone on the same playing field. Perhaps the most problematic part of the C language for many are these things called pointers. The C language provides the asterisk as an operator for getting the value. The opaque pointer is allowed to assume the role of a pointer to int, pointer to float, or pointer to whatever, as in the following code fragment: If this brief review of pointers and structures isn't enough, refer to one of the zillion books written on the C language. It gives great flexibility to get at the low levels of the machine, but with that comes the ability to crash the system.