basic.echo
Toggles terminal echo.
Syntax
echo {off|on|num.expression}
Description
toggles terminal echo on or off.
Typically, terminals attached to the system operate in 'echo plex' or 'full duplex' mode. Characters typed at a terminal are sent directly to the computer and must be 'echoed' back to the terminal before they are displayed on the screen.
'echo off' stops this echoing; that is, characters entered at the terminal are not seen on the screen. However, the characters are sent to the computer and processed as usual; also, any output that originates within the computer is displayed on the screen.
'echo on' returns to the normal mode of full duplex echoing.
An expression that returns zero is equivalent to 'echo off'. Any other value returned is equivalent to 'echo on'.
Example
crt 'enter password ' :
echo off
input password
echo on
The password does not display as it is being typed in. Once the password is
accepted, 'echo' is enabled.
secure = userrec<5>
echo secure >= 6
Echo is disabled if the 'secure' variable is 5 or less. Echo is
enabled for 6 or more.
echo off
...
input string
On systems being run in 'half duplex', there is no need to echo the
character to the terminal display. The terminal has already taken care of
display. This proves invaluable when terminals are connected through networks
or complicated multiplexing.
See Also
User Comments
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