6530 Programmer's Guide

Overview
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6530 Programmer’s Guide
Character input from the keyboard occurs at the cursor location on the
currently displayed page. Each page has its own cursor, and the cursor
for a particular page can be moved without affecting the cursors on other
pages. The cursor location is addressed by row and column positions
relative to the page. The default cursor address is the home location
(row 1, column 1).
When a new page is displayed, the cursor moves to the cursor location
stored for that page. This location may be the same as when the page was
last displayed, a new location set by your application, or the default
home position.
The user can only modify data at the currently displayed page and only at
the current cursor location. Your application program, however, can
select any page for I/O. For example, while the user is displaying and
modifying data on page 1, your application program can read and write
to page 3. However, no I/O can be performed across page boundaries. A
new page must be selected before its contents are accessible.
Your application program uses buffer addresses for writing data to the
currently selected page. Buffer addresses are also row and column
positions within the page. The current buffer address is independent of
the cursor address for that page and may be the same or different on each
page. All explicit cursor movement operations initiated by your program
reference the cursor position on the selected page.
Display memory is organized in the same manner for both protect and
nonprotect submodes. Protect submode adds the additional functionality
of fields. Your application can define any contiguous subset of character
positions on a page as a field. Each field can then be assigned its own
video and data attributes.
The cursor cannot be positioned into a protected field, either from the
keyboard or from your application. An attempt to place the cursor in a
protected field results in the cursor moving to the first position of the
next unprotected field. Because your application uses buffer addressing
for I/O, it can write into any position on the page.