Răspuns:
Program SumaCifrelor;
var n,r,s : integer;
f : text;
begin
assign(f,'DATE.IN');
reset(f);
readln(f,n);
close(f);
if n<=999999999 then begin
while n<>0 do
begin
r:=n mod 10;
s:=s+r;
n:=n div 10;
end;
end;
assign(f,'DATE.OUT');
rewrite(f);
write(f,s);
close(f);
end.
Explicație: