Open System Services System Calls Reference Manual (G06.29+, H06.08+, J06.03+)

Files termcap(4)
Cursor Motions
If the terminal has a fast way to home the cursor (to the upper left-hand corner of the screen), this
can be given as the ho capability. Similarly, a fast way of getting to the lower left-hand corner
can be given as the ll capability; this way can involve going up with the up capability from the
home position, but an application should never do this itself (unless ll does), because it can make
no assumption about the effect of moving up from the home position. Note that the home posi-
tion is the same as cursor address (0,0): to the top left corner of the screen, not of memory.
Therefore, the \EH sequence on Hewlett-Packard terminals cannot be used for the ho capability.
Area Clears
If the terminal can clear from the current position to the end of the line, leaving the cursor where
it is, this should be given as the ce capability. If the terminal can clear from the current position
to the end of the display, this should be given as the cd capability. cd must be invoked only from
the first column of a line. (Therefore, it can be simulated by a request to delete a large number of
lines, if a true cd capability is not available.)
Insert/Delete Line
If the terminal can open a new blank line before the line containing the cursor, this should be
given as the al capability; this action must be invoked only from the first position of a line. The
cursor must then appear at the left of the newly blank line. If the terminal can delete the line that
the cursor is on, this should be given as the dl capability; this action must be used only from the
first position on the line to be deleted. Versions of al and dl that take one parameter and insert or
delete the indicated number of lines can be given as the AL and DL capabilities.
If the terminal has a settable scrolling region (like the DEC VT100 terminal), the command to set
this can be described with the cs capability, which takes two parameters: the top and bottom lines
of the scrolling region. The cursor position is, therefore, undefined after using this capability. It
is possible to get the effect of insert or delete line using this capability — the sc and rc (save and
restore cursor) capabilities are also useful. Inserting lines at the top or bottom of the screen can
also be done using the sr or sf capability on many terminals without a true insert/delete line
feature, and sr and sf are often faster even on terminals with insert/delete line features.
Terminals with the "magic cookie" glitches (the sg and ug capabilities), rather than maintaining
extra attribute bits for each character cell, instead deposit special cookies, or garbage characters,
when they receive mode-setting sequences, which affect the display algorithm.
Some terminals, such as the Hewlett-Packard 2621 terminal, automatically leave standout mode
when they move to a newline or when the cursor is addressed. Applications using standout mode
should exit standout mode on such terminals before moving the cursor or sending a newline. On
terminals where this is not a problem, the ms capability should be present to indicate that this
overhead is unnecessary.
If the terminal has a way of flashing the screen to indicate an error quietly (a bell replacement),
this can be indicated by the vb capability; this action must not move the cursor.
If the cursor needs to be made more visible than normal when it is not on the bottom line (to
change, for example, a nonblinking underline into an easier-to-find block or blinking underline),
indicate the vs capability. If there is a way to make the cursor completely invisible, indicate the
vi capability. The ve capability, which undoes the effects of both of these modes, should also be
specified.
If your terminal correctly displays underlined characters (with no special codes needed), even
though it does not overstrike, then you should specify the ul capability. If overstrikes can be
erased with a blank, indicate that by specifying the eo capability.
527186-023 Hewlett-Packard Company 11−59