The CHECK attribute specifies error-checking options that are to
  be enabled during program execution.

  Syntax:

     CHECK [[( {identifier},...  )]]

  An identifier specifies an option to be enabled.   If  you  omit
  the list of options, all available positive options are enabled.

     ALL                 Enables all forms of checking.

     NONE                Suppresses all checking code.

     [NO]BOUNDS          Verifies that an index expression is within
                         the bounds of an array's index type and that
                         character-string sizes are compatible with
                         the operations being performed and that
                         schema types are compatible.

     [NO]CASE_SELECTORS  Verifies that the value of a case selector
                         is contained in the corresponding case
                         label list.

     [NO]DECLARATIONS    Verifies that schema definitions yield
                         valid types and that uses of GOTO from
                         one block to an enclosing block are correct.

     [NO]OVERFLOW        Verifies that the result of an integer
                         computation does not exceed the machine
                         representation.

     [NO]POINTERS        Verifies that the value of a pointer
                         variable is not NIL.

     [NO]SUBRANGE        Verifies that values assigned to variables
                         of subrange types are within the subrange;
                         verifies that a set expression is assignment
                         compatible with a set variable.

  See the "HP Pascal Language Reference Manual" for  the  complete
  description of using the CHECK attribute.