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the screen, pressing this key moves the cursor to the
rightmost column in the next higher row (from the leftmost
column in the top row of the screen, the cursor moves to the
rightmost column in the bottom row of the screen).
To perform this function programmatically, use the follow-
ing escape sequence:
<ESC>D
Roll Text Up
Each time you press the
II
key, the text in display mem-
ory rolls up one row on the screen. The top row rolls off the
screen, the remaining data rolls up one line on the screen,
and a new line of data rolls from display memory into the
bottom line of the screen. If you hold this key down, the text
continues to roll upward until you release the key or until
the final line of data in display memory appears in the top
row of the screen. In the latter case, pressing or continuing
to hold down the key has no further effect. The "roll up"
function is illustrated in figure 4-1a.
To perform this function programmatically, use the follow-
ing escape sequence:
<ESC>S
Roll Text Down
Each time you press the
II
key, the text in display mem-
ory rolls down one row on the screen. The bottom row rolls
off the screen, the remaining data rolls down one line on the
screen, and a new line of data rolls from display memory
into the top line of the screen. If you hold this key down, the
text continues to roll downward until you release the key or
until the first line of data in display memory appears in the
top row of the screen. In the latter case, pressing or continu-
ing to hold down the key has no further effect. The "roll
down" function is illustrated in figure 4-1b.
To perform this function programmatically, use the follow-
ing escape sequence:
<ESCH
Next Page/Previous Page
The data in display memory can be accessed (displayed on
the screen) in blocks that are known as "pages". Generally
speaking, a page consists of 24 lines of data. The current
page is that sequence of lines which appears on the screen
at any given time. The previous page is the preceding 24
lines in display memory. The next page is the succeeding 24
lines in display memory.
If the memory lock function is being used to "lock" some
number of lines on the display screen, then a page consists
of the number of "unlocked" lines on the screen. For ex-
ample, if ten lines of data are "locked" on the screen, the
current page consists of the 14 "unlocked" lines visible on
the screen. The previous page is the preceding 14
"unlocked" lines in display memory. The next page is the
succeeding 14 lines in display memory.
The concept of display "pages" is illustrated in figure 4-2.
------
PREVIOUS
PAGE
DISPLAY
SCREEN
NEXT
PAGE
- - - - - - -
Display Control
DISPLAY
MEMORY
Figure 4-2. Previous Page and Next Page Concepts
Pressing the
6lD
key rolls the text in display memory up so
that the next page of data replaces the current page on the
screen. If you hold the key down, the operation is repeated
until you release the key or until the final line in display
memory appears in the top line of the screen. In the latter
case, pressing or continuing to hold down the key has no
further effect.
To perform the "next page" function programmatically, use
the following escape sequence:
<ESC>U
Pressing the
BiB
key rolls the text in display memory down
so that the previous page of data replaces the current page
on the screen. If you hold the key down, the operation is
repeated until you release the key or until the first line in
display memory appears in the top line of the screen. In the
latter case, pressing or continuing to hold down the key has
no further effect.
To perform the "previous page" function programmati-
cally, use the following escape sequence:
<ESC>V
At the completion of the "next page" or "previous page"
function, the cursor is positioned at the left margin in the
top line of the screen.
4-3
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