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Pathway/iTS System Management Manual (G06.24+)

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HP NonStop Pathway/iTS System Management Manual—426748-002
F-1
F
Setting the DISPLAY-PAGES
Parameter
This appendix explains how to calculate the DISPLAY-PAGES parameter of the
SET TERM and SET PROGRAM commands.
Screen Caching
The DISPLAY-PAGES parameter specifies the depth of the terminal’s screen caching.
The 6520, 6530, and 6540 terminals and terminal emulators have screen caching
capability to increase performance. Performance is improved because screen caching
prevents a screen from being built a second time after the initial building of the screen.
For example, when the first DISPLAY BASE operation for Screen A is executed, all the
terminal escape sequences needed to build the screen are written to the terminal. The
terminal stores the screen image and field definitions in its memory. When the next
DISPLAY BASE operation for Screen A is done, only a few escape sequences—
enough to display the stored screen—are written to the terminal. Such screen caching
results in a significant savings in terminal process time.
Terminal Memory Organization
The value of the DISPLAY-PAGES parameter affects how the terminal’s fixed amount
of RAM (random access memory) is used. RAM is divided into two separate areas: the
screen-image area and the field-attribute entries area. There is one screen-image area
associated with a screen definition and approximately two field-attribute entries
associated with each field definition. A field-attribute entry is an entry in a table that the
terminal maintains to record field characteristics (for example, brightness or blinking
versus non-blinking).
The DISPLAY-PAGES parameter determines how much terminal memory is used for
the screen-image area compared to how much is used for the field-attribute entries
area. The more memory assigned to one, the less available to the other.
Figure F-1 on page F-2 illustrates a terminal’s RAM organization with a DISPLAY-
PAGES setting of 3. The RAM space reserved in the screen-image area stores the
image of Screen A, Screen B, and Screen C. The remainder of the RAM is used to
store the field-attribute entries for each screen field.
Note. For more information on the SET TERM and SET PROGRAM commands, including
syntax descriptions, see Section 10, TERM Commands, and Section 11, PROGRAM
Commands.