;ALTERNATE PDP-10 MNEMONICS.
	OPDEF DIP[HRLM]↔OPDEF DAP[HRRM]↔OPDEF CAR[HLRZ]↔OPDEF CDR[HRRZ]
	OPDEF LAC[MOVE]↔OPDEF DAC[MOVEM]↔OPDEF DZM[SETZM]↔OPDEF DOM[SETOM]
	OPDEF FLOAT[FSC 233]↔OPDEF FIXX[FIX 233000]↔OPDEF GO[JRST]
;RETURN FROM AN N-ARGUMENT SUBROUTINE CALL.
	↓P←←17
	DEFINE POP0J<POPJ P,>
	↓POP1J.:↔SUB P,[2(2)]↔GO@2(P)↔DEFINE POP1J<GO POP1J.>
	↓POP2J.:↔SUB P,[3(3)]↔GO@3(P)↔DEFINE POP2J<GO POP2J.>
	↓POP3J.:↔SUB P,[4(4)]↔GO@4(P)↔DEFINE POP3J<GO POP3J.>
	↓POP4J.:↔SUB P,[5(5)]↔GO@5(P)↔DEFINE POP4J<GO POP4J.>
;ACCUMULATOR AND TEMPORARY DATA MANAGEMENT.
	DEFINE ACCUMULATORS(LIST){ACPTR←←2	;DECLARE ACCUMULATORS.
	FOR AC⊂(LIST)<AC←ACPTR↔ACPTR←←ACPTR+1↔>}
	DEFINE SAVAC $(N){LAC[XWD 2,[AC2: FOR I←2,N{0↔}]]↔BLT AC2+N-2}
	DEFINE GETAC (N){LAC[XWD AC2,2]↔BLT N}
;FATAL ERROR MESSAGE.
	DEFINE FATAL(STR){PUSHJ 17,FATAL.↔ASCIZ/STR/}
	FATAL.:OUTSTR[BYTE(7)15,12(21)"FAT"↔"AL - "⊗1↔0]
	OUTSTR @(17)↔INCHRW↔GO .-1↔LIT
	DEFINE CRLF{OUTSTR[BYTE(7)15,12]}
;SAIL LIKE SUBROUTINE LINKAGE.
	%←400000
	DEFINE CAT $(A,B){A$B}	;CONCATENATION.
	.PLEVEL←←0 ↔ .SLEVEL←←0	;PDL COUNT & DEPTH OF SUBR NESTING.
;SUBROUTINE DECLARATION MACROS  -  SUBR & ENDR.
;(Reminder: Right-arrow, "→" is FAIL's macro arg EVAL).
	DEFINE SUBR(NAME,X1,X2,X3,X4,X5)↔{BEGIN NAME↔INTERN NAME
	GLOBAL .PLEVEL↔GLOBAL .SLEVEL↔.SLEVEL←←.SLEVEL+1
	CAT(.SBR,→.SLEVEL)←←.PLEVEL     ↔.PLEVEL←←.PLEVEL+1
	IFDIF<><X1>{DEFARG(X1,→.PLEVEL) ↔.PLEVEL←←.PLEVEL+1
	IFDIF<><X2>{DEFARG(X2,→.PLEVEL) ↔.PLEVEL←←.PLEVEL+1
	IFDIF<><X3>{DEFARG(X3,→.PLEVEL) ↔.PLEVEL←←.PLEVEL+1
	IFDIF<><X4>{DEFARG(X4,→.PLEVEL) ↔.PLEVEL←←.PLEVEL+1
	IFDIF<><X5>{DEFARG(X5,→.PLEVEL) ↔.PLEVEL←←.PLEVEL+1}}}}}
	XWD 777000+.PLEVEL-CAT(.SBR,→.SLEVEL)-1,[SIXBIT|NAME|]
	↓NAME:;}
;DEFINE ARGUMENT NAME MACRO.
	DEFINE DEFARG(NAME,LEVEL){DEFINE NAME{LEVEL-.PLEVEL(17)}}
;SUBROUTINE TERMINATION MACRO.
	DEFINE ENDR{.PLEVEL←←CAT(.SBR,→.SLEVEL)
	.SLEVEL←←.SLEVEL-1↔LIT↔BLOCK 0↔BEND }
;SUBROUTINE CALLING MACROS  -  CALL & SETQ.
	DEFINE CALL(NAME,X1,X2,X3,X4,X5)
	{GLOBAL .SLEVEL,.PLEVEL↔.SLEVEL←←.SLEVEL+1
	CAT(.SBR,→.SLEVEL)←←.PLEVEL
	IFDIF<><X1>{PUSH P,X1↔.PLEVEL←.PLEVEL+1
	IFDIF<><X2>{PUSH P,X2↔.PLEVEL←.PLEVEL+1
	IFDIF<><X3>{PUSH P,X3↔.PLEVEL←.PLEVEL+1
	IFDIF<><X4>{PUSH P,X4↔.PLEVEL←.PLEVEL+1
	IFDIF<><X5>{PUSH P,X5↔.PLEVEL←.PLEVEL+1 }}}}}
	IFDIF<><NAME>{PUSHJ P,NAME }
	.PLEVEL←←CAT(.SBR,→.SLEVEL)↔.SLEVEL←←.SLEVEL-1}
	DEFINE SETQ(VAR,LIST){CALL(LIST)↔DAC 1,VAR}
;STACK ACCESSING MACROS  -  PUSHP & POPP.
	DEFINE PUSHP(ARG){PUSH P,ARG↔.PLEVEL←←.PLEVEL+1}
	DEFINE POPP(ARG) {POP  P,ARG↔.PLEVEL←←.PLEVEL-1}