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Taken together, these numbers and their meanings make up
the ASCII code (pronounced ask-key), which stands for the
American Standard Codefor Information Interchange. There are
ASCII codes for all the letters of the alphabet (upper case and
lower case), Oto 9, most punctuation marks, and some (but not
all) of the functions of the printer.
There are a number of different ways to represent an ASCII
code, depending on how you are using it. For example, the
ASCII codes for the upper-case letter “A” are 65 (decimal) or
&H41 (hexadecimal). Or you can just call it “A”. Appendix B
shows all of the ASCII codes.
BASIC uses the CHR$ function to represent ASCII
characters and many functions. To print the letter “A” we
would enter LPRINT CHR$(65). To make the printer’s bell
sound, we would enter LPRINT CHR$(7). In general, we print a
character by entering LPRINT CHR$(ASCII code) to the
printer.
We can also use hex ASCII codes. Although we use only
decimal ASCII codes in this manual, in some applications it will
help if you understand what a hex code is. “Hex” is short for hex-
adecimal and refers to a base-16 number (the numbers we use in
everyday life are base 10). Since the hex system needs 16 digits,
it uses the numerals Othrough 9 and also the letters A through
F. In BASIC programs, you can always tell that a number is in
hexadecimal by the “&H” immediately preceding it. The ASCII
code for the letter “A” (65 in decimal) is &H41 in hex.
■ Control codes
ASCII codes with values of 32 or less do not correspond to
keys on the keyboard. These codes control many of the printer’s
functions, so we call them control codes. To enter a control code
from the keyboard, we have to press two keys at the same time
—
the “control” key and one other. The other key determines
what code is sent – pressing the control (CTRL) key and A
sends ASCII code 1, CTRL B sends ASCII code 2, and so on.
Your printer has a lot of control codes to let you do some
useful things. Let’s try one that we’ve mentioned several times
already:
10 ‘ Demo of ASCII
code
20 LPRINTCHR$(7)
30 END
RUN