program abcxyz;
uses crt;
var a,aa,b,bb,s,ss: longint;
begin
clrscr;
write('nhap mot so bat ki a:'); readln(a);
write('nhap mot so bat ki b:'); readln(b);
aa:=a;
s:=0;
while a<>0 do
begin
  s:=s*10+a mod 10;
  a:=a div 10;
end;
writeln('so doi xung cua   ',aa,'   la:',s:4);
bb:=b;
ss:=0;
while b<>0 do
begin
  ss:=ss*10+b mod 10;
  b:=b div 10;
end;
writeln('so doi xung cua   ',bb,'   la:',ss:4);
writeln('tong doi xung cua hai so a,b la:   ',s+ss);
readln
end.

{Var x,xx,y,yy,s,ss: longint;
Begin
Write('Nhap mot so bat ki x:'); readln(x);
write('nhap mot so bat ki y:'); readln(y);
xx:=x;
s:=0;
while x<>0 do
begin
  s:=s*10+x mod 10;
  x:=x div 10;
end;
writeln('so doi xung cua   ',xx,'   la:',s:4);
yy:=y;
ss:=0;
while y<>0 do
Begin
  zz:=zz*10+y mod 10;
  y:=y div 10;
end;
writeln('so doi xung cua   ',yy,'   la:',zz:4);
writeln('tong doi xung cua hai so x,y la:   ',z+zz);
readln
end.}

Program và uses Crt k cần thiết nhé !