阅读下述程序,指出宏指令ABC的功能是 ______。 1 ABC MACRO X1,X2,X3 2 LOCAL CONT 3 PUSH AX 4 MOV AX, X1 5 SUB AX, X2 6 CMP AX, 0 7 JGE CONT 8 NEG AX 9 CONT: MOV X3, AX 10 POP AX 11 ENDM 12 DATA SEGMENT 13 XDW 32 14 Y DW 98 15 Z DW 16 DATA ENDS 17 CODE SEGMENT 18 ASSUME CS:CODE,DS:DTAT 19 BEGIN: MOV AX, DATA 20 MOV DS,AX 21 ABC X,Y,Z 22 MOV AH, 4CH 23 INT 21H 24 CODE ENDS 25 END BEGIN