Chapter 61 Changing - Tandy TRS-80 Owner Manual & Programming Manual

CHANGING
IT
ALL
AOUND
BO
OPEN "0". »lf
"MEMBERS/DAT"
90
GOSUB 430
100 IF
N*="" THEM
CL0SE«1:END
110
WRITE
*1
i
N$t A*.
P*
120
GOTO
90
430 CLS:
PRINT "PRESS <ENTER> WHEN
FINISHED" :PRINT
440 INPUT "NAME OF MEMBER: "iN$
450
IF N$
=
""
THEN 480
4G0 INPUT "ADDRESS
: "
?
A*
470 INPUT "PHONE NUMBER :"!
P$
480
RETURN
Now
finish
it
by
solving
this
Programming
Exer-
cise.
It'll
be
difficult,
but
we
think you can
do
it.
Remember, no
one's
watching.
If
you
get
bogged
down,
refer to
the
answer
in
Appendix
A
for help.
PROGRAMMING
EXERCISE
#6.3
Write
a
program
in
which you
can:
1.
See
the
names,
addresses,
and
phone numbers
of
your
club's
members.
2.
Change
the addresses of
some
of
the
members.
3.
Add new
members.
4.
Delete
some
of
the
members.
All of this
works
quite well
on
a small
scale,
but
how
would
it
work
in a large
file?
What
if
you had
500
members
in
your
"MEMBERS/DAT"
file
and
you wanted
to
change only the address
of
the
453rd
member?
The
process
would
still
be the same.
You
would
have
to
input each
of the
500
members
from one
file
and
then output
them
all
to
another
file.
All of
this
just to
change one
record.
There
must
be
an
easier
way!
The
easier
way
is
called
the direct access
method
of
programming.
It
makes
your
files
easier
and
faster to update, but in
many
cases
it
will
make
them
take
up more
space
in
your
disk.
The
choice
is
yours. We'll talk about
direct access in
the next
chapter.
Note: We've demonstrated
short
example programs.
There
are
many
ways you
could improve them. See
the
"Sample Programs"
in
Appendix C
for ideas.
CHAPTER CHECKPOINT
Why
can
't
you
input
and
output data
to
the
same
buffer at the
same
time?
Can you
input data from a
file
OPENed
for
"O"—
output?
31