Should be x, y is an integer of integer variable x= 1.2, then x =1; Y=( 1+3.8)/5.0 (note that x= 1 is calculated at this time) is rounded, and then y=0 outputs d*y in the format of %f (note that D is a double type and Y is an int type, and the two are multiplied, and d*y is a double type, where Y is converted from int by type coercion.