E - error recovery.

e - Error recovery.: If an I/O error occurs on the unit any time after it has been opened, control returns to the user. Normally OPEN sets up the I/O unit so that the program EXITs with an error message if an I/O error occurs. If a program specifies error recovery, it must check for error statuses on all subsequent I/O calls (READ, WRITE, PUTCHAR etc.).
See the "f" option of OPEN to recover from errors that may arise during the OPEN operation itself.