Chapter
5
BASIC
CONCEPTS
This chapter describes the different ways BASIC handles and
manipulates data. By understanding how BASIC does this, you
can build more efficient programs.
Elements
of
a Program
A program is a group of instructions that performs a certain
task.
It
is made up of
1
or more numbered lines.
Each line can contain a maximum
of
255
visible characters. Of
the
255
characters, BASIC automatically reserves
1
space for
each digit in the line number and another space for the space fol-
lowing the line number.
If
you enter more than
255
visible char-
acters, BASIC truncates the line.
Here is a sample program line:
10 PRINT
"one"
A
line
number
is always the first element
of
a program line. In
BASIC line numbers must be in the range
0
to
65529.
In the
sample program line, the line number is
10.
A BASIC
statement
follows the line number. A statement tells
BASIC to perform a specific operation. In the sample program
line, the statement
is
PRZNT
"om".
This statement tells BASIC
to print, or display, the word
om
on the screen.
You
can have more than
1
statement on a program line by plac-
ing a colon between each statement. For example:
20 FOR
X
=
1
TO
5:PRINT
"one":NEXT
X
This program line has
3
statements. They are:
1.
FORX
=
1TO5
2.
PRINT "one"
3.
NEXTX
You
can add explanations, or
remarks,
to
your program lines. A
remark is preceded by a single quotation mark to separate it
from the statements. Here
is
a program line with a remark:
20
FOR
X
=
1
TO
5:PRINT "one":NEXT
X
'loop
43
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