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Table 1. Functions of 2265 Display Station Keys (Nondestructive Cursor) (Cont)
Key
No Shift
Shift
ERASE DPLY
Erases entire display, places an SOM symbol
Same
(Erase Display)
in upper left corner of display (first display-
able character position), and cursor in second
character position.
ERASE E0L
Erases all characters, beginning with position in
Same
(Erase to End of Line)
which cursor is located and continuing to end
of that line. Cursor does not move.
,
Erase EOS
Erases all characters, beginning with position in
Same
(Erase to End of Screen)
which cursor is located and continuing to end
of screen. Cursor does not move.
TEST
Isolates 2845 data set and initiates internal
Same
"wrap" test.
TAB
Initiates a search for a colon. Search begins
Same
with cursor's present position. When a colon
is detected, cursor is positioned to character
position immediately following colon. No
characters are erased.
If no colon is detected before end of screen
is reached, cursor is positioned to upper
left corner of display (first displayable
character position).
NL symbol has no effect on tab operation.
If no Tab feature is installed, no operation
occurs.
Destructive Cursor Symbol (Feature)
The destructive cursor symbol appears on the screen of
the 2265 as a heavy horizontal bar (-); it marks the
display position that the next character entered will occupy.
Table 2 explains the effect of each keyboard key on the
destructive cursor symbol. When the destructive cursor is
advanced, backspaced, or otherwise moved to a character
position containing a character, the character is erased.
The movement of the destructive cursor symbol and its
position relative to other display characters during the
time data is entered from the 2265 keyboard are described
under "Control Key Functions".
PROGRAMMING NOTE: Whether the nondestructive cursor
symbol or the destructive cursor symbol is being used as a 2265
display position marker, the EOM symbol will appear on the 2265
screen in the position occupied by the cursor when the keyboard
ENTER key is depressed (as in manual input operations) or when
the PRINT key is depressed.
To ensure correct manual input operations when the
nondestructive cursor is used, the EOM symbol should be
deleted from the 2265 screen between message transfers.
This can be accomplished through programming (by issuing
an Erase/Write following a Poll command) or by the
operator at the keyboard (by overwriting the EOM symbol).
End of Message (EOM) Symbol
Whether or not the 2845 is equipped with the Destructive
Cursor Feature, the EOM symbol (_) designates the end
of a message. In appearance it is identical with the
destructive cursor symbol. The EOM symbol is displayed
by depressing the ENTER key or the PRINT key or by
transmitting -the EOM code from the I/O channel to the
2265. The latter course should be avoided since the
presence of both an EOM symbol and a destructive cursor
symbol can be confusing to a viewer and can cause an
operation to be prematurely terminated. However, when
a message is transmitted from the I/O channel to the 1053
Printer, the EOM code should be transmitted as the last
character to denote the end of the message. The EOM
code is printed by the 1053 Printer as an EOM symbol and
it also causes a 1053 carriage return/line feed function.
The differences between an EOM symbol and the
destructive cursor symbol are:
1. The cursor denotes the display position that the next
character entered will occupy. The EOM symbol
denotes only the end of a message.
2. The cursor advances as data is entered and can be moved
about the 2265 screen. The EOM symbol, when dis-
played, remains stationary.
3. The cursor is automatically inserted and is displayed
at all times. The EOM is displayed only when the
ENTER or PRINT key is depressed or when its code
is transmitted from the I/O channel to the 2265.
4. Only one cursor symbol may be validly displayed on
a 2265 screen, whereas it is possible to display
multiple EOM symbols.
While the viewer must rely on operation observation
to distinguish the destructive cursor from an EOM
symbol, the distinction within the 2845 Display Control
is performed electronically.
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