Radio Shack TRS-80 User Manual page 128

Get
the idea?
Can you
see
the beginning of a simple inventory system for a
small business?
Let's
go one small step {for
mankind)
further.
Suppose you know
the color
of each of the
10
cars,
and
for simplicity,
suppose they
are
coded
1,
2,
3
and
4.
We
might then have a
master
chart that looks
like this:
LICENSE
#
1
2
3
4
10
ENGINE
SIZE
300
200
500
300
20p
300
400
400
300
500
COLOR CODE
3
1
4
3
In the
language of
professional
computer
types,
this
is
called a matrix.
A
matrix
is
just
an
array that has
more
than
one dimension.
(Our
first
array
had
the
dimension
of 1
by
10.)
This array has
a
horizontal
dimension of 2
and
a vertical
dimension
of 10. If
you wanted
to be terribly inefficient
about the matter,
you
could say that
this
is
a 3
by 10
array,
count-
ing the license
number.
If so,
then our original
one would have been a 2
by
10 array
—
but
who
needs
it?
As long
as
we keep our
license
numbers
in
a simple
1
to 10
FOR-NEXT
loop,
and our
DATA
in
proper sequence,
we
can keep our arrays
simpler
and
easier to
handle.
How
then can
we handle
this 2
by 10
matrix?
We
have already used
up our
A
array
ele-
ments
numbered
1
through
10.
Oh,
you want
to
know how many
array
elements
we
have to
work
with?
Very
good!
What was your
name
again? (Let
me mark
that
down.)
Assuming
you
left
our
last
program untouched, type:
126
ENGINE
SHE?
WHAT
ENGINE?'
You
might want to think of
a
matrix
as
a chart
with a certain
number of
columns
of informatjon.
First
you
set
up
the chart,
then
how many
columns of info
can
you
get in
. .
.?
-
•