IBM 3164 ASCII Manual page 39

Chapter 3. Keys and messages
Insert line (Ins Ln) key
3-14
If the Insert Character Key option is off and you press this key, you enter the (
insert character state. To exit from this state, you must press either a send .
(Send, Send Message, or Send Line) key, a PA key, a Function key (except
when a Function key has a predefined data stream), the Clear key, the Insert
key, or the Reset key. You can insert characters only when the cursor is
located in an unprotected field having a null character either in the character
location identified by the cursor or in any character location in the field
beyond the cursor. The character formerly occupying the cursor location and
all remaining characters within the field (except for null characters) are shifted
one character location to the right. If the location identified by the cursor at
the time of the insert operation is a null, character shifting does not occur and
the MDT bit is set to 1 .
When you press an alphanumeric key after all characters at or beyond the
cursor in the field (from the current cursor position to the end of the page for
the unformatted page) have been overwritten, or if there are no more null
characters in the field, the audible alarm sounds and WRONG PLACE is
displayed in the operator information area.
When you press an alphanumeric key when the cursor is located at an
attribute character position within a protected field, .the audible alarm sounds
and WRONG PLACE is displayed in the operator information area. If a field
has more than one line of characters, the character at the last position of the
line is shifted to the first character position of the next line.
In echo mode, INSERT is displayed and no other function is performed at
this point. After that, the Insert Character response is sent to the host
whenever an alphanumeric key is pressed.
In character mode, INSERT is displayed and no other function is
performed at this point. After that, when an alphanumeric key is pressed,
the insert operation is performed in the same way as described above and
the I nsert Character response is sent to the host.
If the I nsert Character Key option is on, the space code is inserted but the
cursor does not move. In echo or character mode, the following sequence is
sent to the host.
ESC. P .sp. BS
< - - - - - -
Backspace code
B~
(Press and hold)
A
~
Inserts a line, depending on the options used
When you press this key, the line that contains the cursor is replaced with a
line of null characters. Data in the current line and in the remaining lower
lines (including the null character lines) move down one line.