Bài 3:

var s1,s2:string;
begin
   write('Nhap ho ten nguoi thu nhat: '); readln(s1);
   write('Nhap ho ten nguoi thu hai: '); readln(s2);
   if s1>s2 then write(s1) else 
   if s1=s2 then write(s2) else write(s2);
   readln
end.

Bài 4: 

var i:byte;
    a,b:string;
begin
   write('Nhap xau: '); readln(a);
   b:='';
   for i:=1 to length(a) do
   if a[i]<>' ' then b:=b+a[i];
   write('Ket qua la: ',b);
   readln
end.

Câu 3:

uses crt;

var st1,st2:string;

d1,d2:integer;

begin

clrscr;

write('Nhap ho ten cua nguoi thu nhat:'); readln(st1);

write('Nhap ho ten cua nguoi thu hai:'); readln(st2);

d1:=length(st1);

d2:=length(st2);

if d1>d2 then writeln(st1);

if d1=d2 then writeln(st2);

if d1<d2 then writeln(st2);

readln;

end.

Câu 4:

uses crt;
var s:string;
      i:integer;
begin
clrscr;
writeln('Nhap vao 1 chuoi bat ki: ');
readln(s);
for i:= 1 to length(s) do
      if s[i] = ' ' then delete(s,pos(' ',s),1);
writeln(s);
readln;
end.