The following will display:
Recs
Bytes
Ext
Acc
VECTOR 4 USER'S
MANUAL
VECTOR 4 CP/M TRANSIENT COMMANDS
"""k
•
xxx
d:SAMPLE.IX::C
Bytes
remaining
on
d:
.,Ik
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The
"Recs" column lists the number of records (128 bytes in each) which make
up
the
file;
the
Bytes
column indicates the number of bytes assigned
to
the
file.
This
last
number will usually
be
more
than
the number of records times
128, because
the
number in the "Bytes" column
reflects
the
maximum number
of
bytes
which can
be
stored in
the
allocation units used for the file.
An
allocation
unit
is a
physical
sectioo
of
the
disk surface, of a
size
which
varies depending
on
the type of disk being used. Basically, the larger
the
disk
capacity,
the
larger
the
allocation
unit.
Floppy
disks,
for
example,
use
allocation units of 2 kilobytes each,
where
Vector
Graphic's
largest
current
hard disk, which measures eight inches, uses allocation units of 8 kilobytes.
Since
the
allocation unit is a physical portion of
the
disk,
it
works much
the
same
way
as a
spiral
notebook: even if only two pages in
the
notebook have
text
written
on them, there
are
still
the
same number
of
blank
pages
left
in
the
notebook,
and
the
notebook
takes
up a
certain
amount
of
space
in a
bookcase.
Allocation
units
can
be
combined; several of them make
up
an
Extent,
which is another way
that
the
BnOS looks
at
file management. There
is
at
least
one
extent
per file;
the
number of extents used in a file is listed
in the
"Ext" column.
The
chief
difference
is
that
an
extent
defines the relationship of
data
in a
file;
the
allocation
unit
defines
the
actual
physical
location
on
the
disk
surface.
It
is
really
no
more
complicated
than
reading
a newspaper story
which begins on
Page 1 and continues on p·age
3,
only
to
have the
story
from
Page
3
be
continued on Page
9,
et
cetera.
The story would
be
the
file which
takes up one extent; each page, another
allocation
unit
where
the
extent
is
continued.
But
again,
you
will
probably never have
to
deal with this unless
you
take
up
programming.
The
extent
and
allocation
units
used
by a
file
give
the computer a
larger
division in which
to
begin searching
for
a file when you
enter
a command,
the
way a
file
clerk
would look in a specific drawer of a particular file cabinet
before trying
to
find a single sheaf
of
papers.
This way
the
computer
can
isolate
to
a
fairly
large
area
of
the
disk before
it
starts
loading
the
file a
character
at
a time.
(For
a
more
complete explanation of
how
files
are
stored and
written
to
disk,
refer
to
the Introduction
to
Vector 4 CP/M in this manual.)
Rev. A -
09-01-82
7100-0001
IX-23
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