An assembler language subroutining system
Horace G. Brown, Jackie A. Campbell · ITNOW · 1969
A programmer writing a large System 360 assembler language program has to consider the problems imposed by the characteristics of the machine, as well as those of the program specification. The basic problem is one of addressability, and the following points arise The system described below offers a solution based on a set of three macros, which jointly absorb these responsibilities. One of these macros is used to enter a subroutine, and the other two define the beginning and end of the subroutine. DO is used to transfer control to the subroutine defined by the operand. The coding generated is as follows routinename IN (no operand) Any subroutine entered via a DO macro must commence with IN and transfer is to the location following the IN macro. All instructions and areas comprising the subroutine must come after the IN statement. There may be only one IN statement, and hence only one entry-point to a subroutine.