can someone explaine this to me?

Given a macro definition as the following, what is the expansion result of a macro 7. invocation like "RDBUFF oE,BUFFER,LENGTH..80"? (5%) RDBUFF MACRO &INDEV, &BUFADR &RECLTH &EOR,&MAXLTH (&EOR NE IF &EORCK ENDIF CLEAR LOOP COUNTER CLEAR X CLEAR A (&EORCK EQ 1) IF LDCH XT&EOR' SET EOR CHARACTER RMO A, S ENDIF (&MAXLTH EQ LDT #4096 SET MAX LENGTH 4096 ELSE SET MAXIMUM RECORD LENGTH +LDT H&MAXLTH ENDIF SLOOP TD X &INDEV TEST IN PUT DEVICE JEQ SLOOP LOOP UNTIL READY RD X &INDEV" READ CHARACTER INTO REG A (&EORCK EQ 1) COMPR AS TEST FOR END OF RECORD JEQ EXIT LOOP IF EOR ENDIF STCH &BUFADR X STORE CHARACTER IN BUFFER TIXR. T LOOP UNLESS MAXIMUM LENGTH JLT SLOOP HAS BEEN REACHED SEXIT STX &RECLTH SAVE RECORD LENGTH MEND