Code chạy Pascal:

var s,s1,tg:string;
i:longint;
function dn(x:string):string;
begin
dn:='';
for i:=1 to length(x) do
dn:=x[i]+dn;
end;
begin
write('nhap xau:');
read(s);
while s[1]=' ' do
delete(s,1,1);
while s[length(s)]=' ' do
delete(s,length(s),1);
while pos(' ',s)<>0 do
delete(s,pos(' ',s),1);
tg:=dn(s);
writeln('xau khi xoa dau cach:',s);
write('xau khi dao nguoc:',tg);
readln;
end.

uses crt;

var S : string; i : byte;

begin

clrscr;

write('Nhap xau S : '); readln(S);

while S[1] = ' ' do

    delete(S, 1, 1);

while S[length(S)] = ' ' do

    delete(S, length(S), 1);

i := 1; while i < length(S) do

    if (S[i] = ' ') and (S[i + 1] = ' ') then

        begin

            delete(S, i, 1);

            i := i;

        end

    else i := i + 1;

write('Xau dao nguoc : ');

for i := length(S) downto 1 do write(S[i]);

end.