* INVARIANCE RULE : 
* IF LEN(string1)<=N1 and LEN(string2)<=N2 THEN
* PADR(string1,N1)-PADR(string2,N2)=PADR(string1-string2,N1+N2)
CLEAR
c='1'
b=0hFF
? PADR(C-C,10)=PADR(C,3)-PADR(C,7)
? PADR(B-B,10)=PADR(B,3)-PADR(B,7)