1. In a computing environment, a method for calling a 16-bit code from a 32-bit subroutine, in which at least one stack frame in a memory stack is allocated to the 32-bit subroutine, comprising the computer implemented steps of: defining a consecutive series of 64K byte boundaries in the stack; providing means for accessing variables and data objects spanning any 64K byte boundary defined in the stack from below the 64K byte boundary; building a parameter list in the stack in 16-bit form; and allocating stack space for data to be used by the 16-bit code.