text: -- 1 
  SET SERVEROUTPUT ON
  
  begin
      dbms_output.put_line('Hello');
  end;
  
  -- 2 
  begin
      dbms_output.put_line('Atilim University' || chr(10) || 'Library Database');
  end;
  
  -- 3 
  declare
      x number;
      y number;
  begin
      x:=5;
      y:=6;
  
      dbms_output.put_line(x+y);
  end;
  
  -- 4 
  declare
      x number;
      y number;
  begin
      x:=5;
      y:=6;
  
      dbms_output.put_line(to_char(x) || '+' || to_char(y) || '=' || to_char(x+y));
  end;
  
  -- 5
  declare
      x number;
  begin
    x:=0;
    
    if x>0 then
      dbms_output.put_line('Positive');
    elsif x=0 then
      dbms_output.put_line('Zero');
    else
      dbms_output.put_line('Negative');
    end if;
  end;
  
  -- 6
  declare
      bool_var boolean;
  begin
      bool_var := true;
  
      if bool_var = true then
          dbms_output.put_line('True');
      elsif bool_var = false then
          dbms_output.put_line('False');
      else
          dbms_output.put_line('Error');
      end if;
  end;
  
  -- 7
  declare
      price_a number;
      book_a varchar2(30);
  begin
      select book_title, price
      into book_a, price_a
      from book
      where isbn = '975220127X';
    
      dbms_output.put_line('The price of ' || book_a || ' is ' || to_char(price_a) || ' TL.');
  end;
  
  -- 8
  declare
      r_date date;
      d_date date;
      delayed_days number;
  begin
      select return_date, due_date
      into r_date, d_date
      from loan
      where loan_id = '130428';
    
      delayed_days := r_date - d_date;
      
      if delayed_days > 0 then
          dbms_output.put_line('The book is delayed for ' || delayed_days || ' days. You have to pay ' || to_char(2*delayed_days) || ' TL.');
      else 
          dbms_output.put_line('The book is returned on time.');
      end if;
  end;