~
If
you want
to
copy a file from one drive to another and rename it at the same
time use the
PIP
program.
3-26
3.7.4
SAVE
(Save
an
area
of
memory)
First
of
all, remember
that
this
is
completely different to the SAVE command
in BASIC. The only feature they have in common
is
that
they store programs
on
disk,
but
there the resemblance ends.
It
enables blocks
of
memory to be
saved as a file
on
a disk. Normally only programmers will use this command,
but
there
is
one case where
it
may be useful
to
even BASIC programmers which
is
described below.
The format for the SAVE command
is
very simple.
SAVE n filename
The filename consists
of
a drivename (if necessary), filename and extension,
in the usual way.
The
'n'
parameter denotes the number
of
"memory
pages" to be saved and
must have a space either side
of
it. The value
is
specified in decimal notation.
One page consists
of
256 bytes
of
data, so the basic method
of
calculating n
is
to
divide the number
of
bytes you want to save by 256
and
round the answer
up
to
the next integer.
For
instance,
if
you want
to
save 300 bytes the number
of
pages (n) would be 2 because 300 divided by 256
is
greater than)1lle but less
than
two.
A frequent use
of
SAVE
is
to write
to
disk a program which has been patched
using the
DDT
program (see section 3.10). When the program
is
loaded with
DDT
the address
of
the next available byte
is
shown as NEXT. You can calcu-
late the number
of
pages
to
SAVE in the following way:
1)
Round the value shown as
NEXT
up
to
the next highest page. Taking as
an
example
if
2C5A were returned by NEXT in DDT, this would give
2DOO
(remembering
that
you are working in hexadecimal notation).
2)
Drop the zeros from the end
of
the rounded value
and
calculate the value
of
the remaining digits in decimal.
In
the example 2D becomes
45
decimal.
3)
Since
DDT
loads programs
at
the beginning
of
the first page
of
memory,
subtract 1
to
allow for this, giving 44 in the example.
If
the file
we
have just patched
is
called FREDDY.COM and lives
on
the D:drive,
the command given
to
write it back to disk will be
C>SAVE
44 D:FREDDY.COM
3-27
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