Abstract: A computer architecture is disclosed which permits intersegment program calls with associated selective allocation of data segments of varying lengths. The calling program controls selective allocation of segments to the called program but the called program controls the lengths of the segments being allocated. In this way, recursive calls to the same program cannot affect the function or data of other programs or of the same program in a previous call. Also allocation of data segments can be postponed until execution resulting in more flexible execution of programs written without knowledge of the details of other co-executing programs.