Tandy TRS-80 Owner Manual & Programming Manual page 61

THIMMING THE FAT
OUT OF
DIRECT ACCESS
f
Jfi€JUM*U*Utf'
off
/ %
bFF!C£/DAT"
record
1
S
APER
1
*office:/dat
Coda,
^&tr/6
MKN$
converts
a
number
to a
coded
string.
Regardless
of
how
long the
number
is,
MKN$
will
always
convert
it
to
a string that
is
five
bytes
long.
For example, change
line
30
to
LSET
a
number
with
more
than
five digits:
30 LSET A$
=
MKN$(12345G7B9)
Erase memory,
KILL
"OFFICE/DAT," and
type
and
RUN
the
program. This
is
what
it
stores
in
your
disk
file:
I
^CfcflCE/mT
9
'
To read
this
program
in,
you need
to
decode
the
string.
LOAD
the "Fielded
INPUT
Program" and
make
these changes
to
it:
10 OPEN
"D"
,
#1
,
"OFFICE/DAT"
,
10
20 FIELD
*i
,
5
AS A*
,
5
AS B$
50
PRINT "RECORD"
R "
:
"
;
CYN(A$)i
B$
and
RUN
it
.
. .
CVN
(in line 50) decodes
A$
to the
number
it
represents.
Note: The Computer
only
sees the
first
9
digits
of
a
number.
It
rounds
the
rent
off.
PROGRAMMING
EXERCISE
#0.3
Write
a
fielded direct
access pro-
gram
which
will
store the popula-
tions of
all
the countries.
Make
each record
contain 15 bytes with
these
two
fields:
1.
country
—
10 bytes
2.
population
—
5 bytes
WBPI^^^H^BOWi^PBBB
--—
5 Jswbu
Ofdc
j*v /23f56>7&7
"OFFICE/
OfiT"
PROGRAMMING
EXERCISE
#9.4
Write a
program
which
will
input
the Hie
you
created
in
Exercise
#9.3.
CHAPTER CHECKPOINT
1.
If
you do
not
specify the record
length,
how
many
bytes
will
each record
contain?
2.
Why
must you
include a
FIELD
line
when
you
LSET
your
data?
3.
Howmanybytes
will
MKN$
convert a
num-
ber
into?
51