This section briefly explains the commands to be found in the Controls sub-menu of the Network menu. All of them are common "control character" functions found on almost all service computers.
Especially on TCP/IP connections, which involve massive buffering on the service computer side, the control characters may take a little while to take effect. In pathological cases, such as /usr/ucb/yes on Berkeley UNIX, the delay could be five minutes or more. Furthermore, the service computer may put itself into states where none of these characters work at all, or where they have a different effect from that advertised.
FLUSH OUTPUT*
The currently running program will appear to complete normally, but no more output from that program will be seen. Rather like throwing away the last section of your newspaper before reading it.
ZAP PROGRAM
Like Interrupt, but even more nasty and hateful to the program running on the other computer.
END OF FILE
Sends an end of file indication. This means different things in different contexts. For instance, end of file should be sent after typing in a mail message on UNIX. Rather like writing for a newspaper and putting a mark at the end of your article for your editor to see.
ERASE WORD
Erase the word right before the cursor in the current line of typing, as if you'd backspaced to the end of the preceding word.
ERASE LINE*
Like Erase Word, but the whole line of typing gets erased, as if you'd backspaced all the way to the beginning of the line.
LITERAL
The next character typed will be interpreted as a text character instead of like a control character, even if it is one. If you can think of a newspaper analogy, then maybe you should be writing this instead of me.
BREAK*
The meaning depends on context. On a modem connection, it may hang up the phone or change the baud rate on the service computer's modem. On a TCP/IP connection, it may be just the same as an Interrupt. In either case, it might also be specially interpreted by the currently running program as a meaningful command-type keystroke. Imagine a newspaper which is printed in a lot of different colors and languages - oh, never mind.
Those controls marked with an asterisk (*) are implemented in a standard OS-independent way on TCP/IP terminal connections; on modem connections, and for controls for which no TCP/IP standard exists, the characters sent are extracted from the operating system description for the computer. On Manual Phone connections, only Interrupt, Flush Output, Break, and Zap Line are allowed, and they are not guaranteed to work. On Manual TCP/IP connections, control characters not marked with an asterisk won't work unless the connection is to a known computer, i.e., was picked from the list of computers rather than having its name or address typed in.
