System Packages Oracle PLSQL

SQL> CREATE OR REPLACE PROCEDURE HelloWorldProcedure AS
  2  BEGIN
  3
  4    htp.htmlopen;                      -- 
  5    htp.headopen;                      -- 
  6    htp.htitle('HelloWorldProcedure'); -- HelloWorldProcedure
  7    htp.headclose;                     -- 
  8    htp.bodyopen;                      -- 
  9    htp.line;                          --
 10    htp.print('Hello world.');         -- Hello world.
 11    htp.line;
 12    htp.bodyclose;                     -- 
 13    htp.htmlclose;                     -- 
 14
 15  END HelloWorldProcedure;
 16  /
Procedure created.
SQL>
SQL>