program hoandoi_ab;
var a,b,c:integer;
begin
readln(a,b);
writeln(a, ' ',b);
c:=a;
a:=b;
b:=c;
writeln(a, ' ',b);
readln
end.
program sln;
uses crt;
var a,b:real;
begin
clrscr;
write('nhap so a');readln(a);
write('nhap so b');readln(b);
write('truoc khi nhap a =',a,'b=',b);
a:=a+b;
b:=a-b;
a:=a-b;
write('sau khi nhap a=',a,'b=',b):10:2;
readln
end.![]()