For the scanf function, if the type of input data does not match the definition, the input value will be ignored and executed. At this time, because variables A, B and C are not initialized, the memory addresses they point to are random, so their values are also random. You scanf find ("%d,% d,% d",&; First, & ampb & amp；; c)； Add a printf ("A =% d, B =% d, C =% d \ n ",a, b, c); You can see that the values of a, b and c are not actually entered.