Table of Contents
Advertisement
DISPLAY MEMORY FUNCTIONS
I~
INTRODUCTION
This section contains information for controlling the
terminal's display memory functions. The display memory
functions change the position of display data or assign
special attributes to blocks or fields of display data. The
special attributes alter the way data is displayed or
transmitted. These functions consist of the following
groups:
•
Display Control
•
Edit Operations
•
Forms Mode
•
Display Enhancements
•
Alternate Character Sets
The following paragraphs describe how to control the
display memory functions from a computer program. Each
of the display functions can also be entered from the
terminal keyboard or read from a cartridge tape. In
addition to escape sequences, most of the display memory
functions have been assigned to special keys on the
keyboard. Refer to the User's Manual for a description of
keyboard functions.
DISPLAY CONTROL
The display control functions are made up of cursor and
display positioning operations. The individual functions
available are as follows:
•
Cursor Sensing
Absolute
Relative
•
Cursor Positioning
Absolute Addressing
Screen Relative Addressing
Cursor Relative Addressing
Space
Backspace
Set Tab
Clear Tab
Tab
Backtab
Set Margins
Home Up
Home Down
•
Display Positioning
Roll Up
Roll Down
Next Page
Previous Page
Display Lock (Memory Lock)
MEMORY ADDRESSING SCHEME
Display memory positions can be addressed using absolute
or relative coordinate values. Display memory is made up
of 80 columns (0-79) and a number of rows determined by
the memory options installed in the'terminal. There can
be as many as 100 lines of 80 characters (5 screens). The
amount of memory in the terminal can be determined
from byte 0 of the primary terminal status (refer to
Section VI). The types of addressing available are:
o
Absolute
•
Screen Relative
•
Cursor Relative
ROW ADDRESSING. Figure 2-1 illustrates the way the
three types of addressing affect row or line numbers. The
cursor is shown positioned in the fourth row on the screen.
Screen row 0 is currently at row 6 of display memory. In
o
1
2
3
4
5
a.l Absolute: row 6
b.l Screen Relative: row 0
Figure 2-1. Row Addressing
c.l Cursor Relative: row-3
2-1
Advertisement
Table of Contents
