Commodore Plus 4 - Page 166

184 Some Programming Techniques
3. Many key functions, such as cursor-control and color-change keys, do not
execute immediately. When you press one of these keys, a special reversed-
image symbol is displayed. These symbols stand for keyboard-controlled
functions that do not execute until the quote mode is turned off and the
command is run.
Insert Mode
When you press the INSERT key, you enter insert mode. While you are in insert
mode, some key functions, such as cursor control and color change keys, do not
execute immediately. When you press one of these keys, a special reversed-image
symbol is displayed. These symbols stand for keyboard-controlled functions that
do not execute in insert mode. They will not execute at all unless they are also in
quote mode. In fact, you end up with a syntax error if you leave one of these
function symbols in a command, so be sure to delete them unless they are in
quotes and you want them to remain.
Insert mode ends when you type as many characters as the number of times you
pressed the INSERT key, when you press RETURN, or when you issue the
ESCAPE O sequence. If you want to get rid of the inserted spaces without
pressing RETURN or typing characters, press the DELETE key until the inserted
spaces are deleted. The DELETE key does not actually start deleting right away.
A reversed T is printed in the inserted spaces until they are all filled.
Note that these deferred restrictions do NOT apply when you are in automatic
insert mode, which you enter by pressing ESCape and A and cancel with ESCape
C.
Table 3-1 shows the keys that do not execute in quote mode. This table also
shows the one-character symbols that represent these keys.
You can directly embed the symbols for most of these functions in quote mode
by pressing the indicated keys. The exceptions are the REVERSEd codes. RE-
VERSEd H, I, and N can be entered in quote mode by pressing CONTROL H, I,
and N. For REVERSEd SHIFTed N and M, leave a blank space in the quote
mode text string where you want one of these functions to appear. Then exit
quote mode and cursor back to the blank space in the text string. Once you are in
position, turn on reverse mode (with CONTROL 9) and press the appropriate
SHIFTed key. The symbol from the chart is displayed in the text string, and the
function is deferred until you execute the command that contains the text string.
Clearing the Screen During Program Execution
You can use the CLEAR key to clear the screen during program execution. To
use this key, press SHIFT/CLEAR in quotes in a command such as PRINT or
INPUT, or use the CHR$ code for the CLEAR key, which is 147.