Hi,
I am try to run this code

data test;
c='';
a = .;
b = 7;
if not missing(c) and (a+b)>6 then l = 'A';
run;

and i have an 'Missing value generated' warning in log,

But
data test;
c='';
a = .;
b = 7;
if c^='' and (a+b)>6 then l = 'A';
run;

in this code I have no warning.

Could you please give me some details about that,
Thank you.