An APL emulator on System/370

The IBM family of APL systems

“…21 Two product offerings came directly out of this work: the interpreter with microcode assist, which could run only on the System/370 Model 145, and an independent interpreter named APUCMS, which could run on any machine running CMS. Instead, they concentrated on an APL interpreter that would run under CMS and optionally use microcode to enhance its performance.…”

The management of operating system state data

“…However the CBMS could be implemented in microcode. The complexity of the proposed CBMS (and hence of the microprogram required to support it) is considerably less than that of the microprogram which was written to implement an APL compiler and interpreter for the IBM System/370 Model 145 [10,11]. Performance tests on this system have shown that the microcoded system performs the interpretation of its parameters about ten times faster than an equivalent software interpretive system, and generally performs the subsequent instruction execution faster.…”

“…While the CBMS functions described in this paper would not be extraordinarily difficult to microprogram, CB field validation could in principle be arbitrarily complex, so a break-out from microcode into machine language field validation subroutines would be a prudent provision. The implementation in [10,11] has this facility.…”