Chapter
3:
Programming the
VIC
20
Computer 101
data input from the keyboard and data output
to
the display. There are also
more complex input/ output statements that control
data
transfer between
the computer and peripheral devices such as cassette units, diskette units,
and printers. These more complex input/ output statements are described in
Chapter
8.
Since
we
have already encountered the
PRINT
statement,
we
will
discuss this statement first.
PRINT
STATEMENT
You can use the word
PRINT
or a question mark to create a PRINT
statement.
Why use
PRINT
instead of DISPLAY
or
some abbreviation of the
word display? The answer
is
that
in the early sixties, when the BASIC
programming language was being created, displays were very expensive and
generally unavailable on medium- or low-cost computers. The standard
computer terminal had a keyboard and a printer. Information was printed
where today it
is
displayed; hence the use of the word "print" to describe a
statement that causes a display.
The
PRINT
statement will display any data. Text must be enclosed in
quotes.
For
example, the following statement will display the single word
"TEXT":
113
PRmT
"TEXT"
or
113
?"TEXT"
To display a number, you place the number,
or
a variable name, after
PRINT. This may be illustrated as follows:
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A:I.,.,10
213
?5
.•
A:I.
The statement
at
line
20
displays the number 5 and then the number
10
on
the same line.
You can display a mixture of text and numbers by listing the informa-
tion to be displayed after PRINT.
Use
commas to separate individual items.
The following
PRINT
statement displays the words
"ONE",
"TWO",
"THREE",
"FOUR",
and "FIVE", followed by the numeral for each
number:
113
?"OHE",1,"TWO",2,"THREE",3,"FOUR",4,"FIVE",5
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