7.0. The Stack In this chapter, the stack and operations manipulating the stack are discussed. Since the stack is external to the REXX language, there are large differences between implementations with respect to the stack. These differences are attempted described in the latter part of this chapter. Another goal of this chapter is to try to describe both the “real” standards and some of the most commonly used de facto standards related to stack operation. Where something is not a part of any defined standard, this is clearly labeled. Also, some liberties have been taken in order to create a coherent vocabulary on a field where very little standardization has taken place.