Commodore Plus 4 - CONTROL; CHAPTER 3 Using Software

BASIC Version 3.5 Commands, Functions, and System Variables 21
and CLEAR—has a unique character-string value that can be called by its CHR$
code. You can use CHR$ values to do anything to the screen output that you can
do by pressing a key, such as changing character colors, turning on reversed-
image mode, or deleting a character.
Printing the CHR$ value to the screen has the same effect as pressing the key.
For example, PRINT CHR$(77) is the same as PRINT "M". This feature of
CHR$ is especially useful when you want to defer the "pressing" of a key. For
example, in a BASIC program the only way to print a message that contains a
quotation mark is to use the CHR$ code for the quotation mark:
PRINT "IBM'S MOTTO IS ";CHR$( 34); "THINK"; CHR$(34)
IBM'S MOTTO IS "THINK"
If you actually press the quotation mark key when you type the line, the
quotation mark opens or closes quote mode:
PRINT "IBM'S MOTTO IS "THINK""
IBM'S MOTTO IS 0
In the second PRINT command example, the computer assumes the quote
before THINK turns off quote mode. The computer also assumes that THINK is
a variable name, which is why the 0 is printed. The only way to print the quotation
mark as a character is to use its character code in a CHR$ function.
The CHR$ function is frequently used in function-key definitions to print a
quotation mark or "press" a RETURN key at the end of the key definition.
Appendix C lists all the CHR$ values. Appendix D contains the standard
ASCII codes that are used by many computers for your reference. To find a
CHR$ value, you can use the ASC function, which finds the code for any key.
CHR$ codes are used in I/O to devices other than the screen as well. The
printable characters are generally the same, but the control functions will be
different with a printer, for example, than with the screen.
Example: PRINT CHR$(S8); A; CHR$(1S9); B Changes the character color to
red, prints the value for A,
changes the character color to
orange, and prints B.
CIRCLE Abbr. cl
CIRCLE color source, center coordinates, x radius, y radius, start arc, end
arc, angle, increment
This graphic mode command draws circles as well as a variety of other shapes.
CIRCLE draws curved shapes such as arcs and ovals. CIRCLE also draws any