All our inputs are characters. What the system can do is convert the input characters into corresponding characters according to your format control requirements. If there is a statement: scanf("%d",&a); Enter 45, and the system will convert the string "45" into an integer. This is all done automatically.

If you want to make a human judgment, it is very simple:

while(c=getchar())

if(c>='0'&&< ='9') It is an integer;

else if(c=='.') It is a real number;

esle It is character data;

This is the case in C language. If it is used in other object-oriented programming, it is also based on this principle, but an exception will be thrown when the input type is incorrect.