Tandy TRS-80 - 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