1012890_0_0_6869.c 1012890_0_0_6869.c(6) : error C2065: “cin” : 未声明的标识符 1012890_0_0_6869.c(24) : error C2065: “cout” : 未声明的标识符 1012890_0_0_6869.c(27) : error C2065: “endl” : 未声明的标识符