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n Control codes
SD-lo/l 5 uses many of the non-printing ASCII codes for
control codes. These codes perform a function rather than printing
a character. Let’s try an easy one right now:
NEW
10 LPRINT CHR$(7)
RUN
Where did that noise come from? That’s SD-lo/l 5’s bell. We
will learn more about it in Chapter 8. We just wanted to illustrate
a code that causes SD-lo/l 5 to perform a function.
n The escape code
There’s one ASCII code that we are going to be using more
than all the rest. This is ASCII 27, which is called escape. In
BASIC it is CHR$(27). With all of SD- 10/l 5’s advanced features,
there weren’t enough single ASCII codes to access all of them.
So escape is used to start sequences of control codes that open
a wider range of functions to us.
While you must call this code CHR$(27) in BASIC, we are
going to refer to it as < ESC > in this book. This will make it
much easier to recognize when we use it.
A typical escape code sequence starts with < ESC > which is
followed by one or more CHR$ codes. As an example, the escape
code sequence to turn on emphasized print is:
<ESC> CHR$(69)
In a program, this would look like this:
NEW
10 LPRINT CHR$(27) CHRS(69);
24) LPRINT "TESTING"
RUN
Try this program. It will print the word TESTING in em-
phasized print.
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