A READERR call has the form
READERR (M)
where M is a logical unit designation as before. It yields the value true if the previous read operation produced a parity error; otherwise it yields the value false.
READERR should not be used for testing the operation of a READ statement. The READ procedure has its own facilities for checking, making multiple attempts in case of errors, and terminating the program if necessary.
WRITERR
A WRITERR call has the form
WRITERR (M)
where M is a logical unit designation as before. It yields the value true if the previous write operation produced a parity error; otherwise it yields the value false.
V. The External Declaration
An external declaration is required for each nonstandard library procedure or procedure compiled separately from the calling program, whether in Algol, Fortran or CODAP. Standard Algol procedures are described in [Section VI]. Note that a CODAP subroutine must take account of the special structure of the Algol calling sequence as described in [Appendix C] or be treated as a Fortran subprogram. The use of Fortran subprograms is described in [Appendix G].