Asynchronous Serial Communications Programmer's Reference Manual (32022-90052)

172 Chapter8
Intrinsics Reference
FCONTROL(12, 13)
You may also want to disable echo if the terminal user
is asked to enter data that you do not want to appear on
the screen, such as a password or lockword.
Additionally, it may be necessary to disable echo if you
are connecting certain non-supported devices to an
asynchronous port.
Echo is not reset at FCLOSE, so your program should
always restore the original echo setting before it ends.
If either of these FCONTROL calls is issued against a
terminal connected via DTC Telnet, the call will return
a CCE condition code but the echoing of read data will
continue.
Echo may be changed locally without the remote host’s
knowledge in a VT connection. Applications run on the
remote side will then receive inconsistent information
about echo status. Hence, altering the echo state locally
in a VT connection is discouraged.
Condition Codes
CCE Request granted.
CCG Not returned by this intrinsic.
CCL Request failed because the file number specified did not
belong to this process or the device is not a terminal.
Additional Discussion
Refer to discussions of FCONTROL(26,27) and FSETMODE in this
manual.