有朋友给了我这个铣平面的程序，我是新手这个开头不懂，请高手解释下：
PROC PINGMIAN(REAL CHANG,REAL KUAN,REAL FANHUI,REAL ANJU_Y,REAL ANJU_Z,REAL SHANGMIAN,REAL XIAMIAN,REAL YULIANG，REAL CHISHEN,REAL CHIKUAN,REAL JINGEI_SHEN,REAL JINGEI_PING,REAL YICHUZ,REAL YICHUY,REAL YI_X,REAL YI_Y,REAL ZHUANJIAO)
DEF REAL QUCHU
DEF INT DAOSHU_SHEN
DEF INT DAOSHU_PING
DEF REAL QIDAO_X
DEF REAL ZHUDAO_X
DEF REAL T_R4
DEF REAL KUAN_
DEF INT JISHU_SHEN,JISHU_PING
DEF FRAME FRA_
DEF INT _G6,_G14,_G15,_G10
DEF REAL ZHONG
IF $P_S==0 GOTOF AL1
IF $P_TOOL==0 GOTOF AL2
。。。
谢谢。