Commodore Plus 4 - CHAPTER 5 Numbers and Calculations

46 The BASIC Language
Parameter Values Default
Mode 0-4 No default
Clear screen option 0 or 1 0
CLR command option CLR No default
1. You can use the GRAPHIC command to switch to any of these modes:
0 text mode
1 high-resolution mode
2 split-screen high-resolution mode
3 multicolor mode
4 split-screen multicolor mode
GRAPHIC 0 switches from a drawing mode to text/graphic mode, in which
letters are uppercase and you can print all the graphic symbols on the fronts of the
keys. If you want to switch to the alternate text mode, in which letters can be both
lowercase and uppercase and in which you can print only the left-side graphic-key
symbols, first switch to text/graphic mode, and then press the SHIFT and K8
keys together or PRINT CHR$(14).
2. If you want to include a screen-clearing option with the mode choice, add a
comma and 1 after the mode number. If you do not add this option, the computer
switches back to whatever was on the screen the last time it was used in the current
computing session.
3. The GRAPHIC command can also release the 12K area devoted to graphic
modes. The first time you access any one of the graphic drawing modes, a 12K
area is set aside for the^graphics screen and your BASIC program is moved above
it. When you return to a text mode, this area remains set aside for graphic mode
use unless you tell the computer to release it. Just issue a GRAPHIC CLR
command to regain use of this 12K of memory.
Note: If you define a function with DEF FN before you execute a GRAPHIC
command, the function subsequently may not execute properly (when FN is
used). In other words, the function definition is not moved properly. Care must
be taken when defining functions and using graphics in a single program.
Note: A graphics screen actually requires only 10K bytes of memory. The
amount removed from BASIC RAM is 12K because the screen must be located
on 8K boundaries. The screen is located from $2000 to $3FFF; its color/lumi
nance memories are located from $ 1800 to $ 1FFF. This leaves the 2K from $ 1000
to $17FF unused, but unavailable for BASIC.