Apple IIe - Page 226

226 Apple lie Us ers Handbook
GR set low resolution
graphics & text
Besides clearing the screen, the GR command also sets the low
resolution "next color " register to 0. This register stores the
numeric value of the next color to be displayed.
The
four lines of text that appear beneath the graphics mode can
be
replaced with 8 more rows of the graphics mode. This extends
the display resolution to 48 x 40 pixels. This switch can be
accomplished by reading or writing to memory location 49234.
The easiest means
of accomplishing this is by poking the
location .
POKE 49234,0
full screen graphics
To
replace the four lines of text without erasing any graphics
information on the screen, read or write to memory location
49235 . Again, this can be accomplished by poking the location .
POKE
49235 ,0 graphics & text
(no erase)
Before any graphics
information can be plotted on the screen, a
color must be selected. This is accomplished through use of the
COLOR command. The correct syntax of this command is as
follows :
COLOR =x
x represents a number between 0 and 255 . The color correspond-
ing to x modulo 16 is selected. For example , if x = 2 or 18 then
color number two is selected. The colors and their associated
numbers are listed in Table 6-1.