Warning about character conversion?
Note, however, that if the INPUT and IF statements are as follows:

2   INPUT @20 TYPE 1. @;  
3   IF TYPE ='1' THEN ...

you will see the following warning:

NOTE: Character values have been converted to numeric  
      values at the places given by: (Line):(Column).  
      3:14   7:19

You've defined TYPE as numeric but used a character constant in the IF expression. The message is the same but it points to a different place.
SAS has trouble trying to ask, "does 1= '1' ?" It warns you that this is troubling.
Then, it does a character to numeric conversion of the character constant to the right of the equal sign.
Now SAS asks, "does 1= 1 ?" This it can do.