298 Macintosh
User's
Handbook
Disks and Disk Drives
The Mac uses diskettes
to
store
and
recall large
amounts
of
information. This technique
is
required because the compu-
ter has only a limited
amount
of
built-in memory.
In
addition,
each time the computer
is
turned off, the major
portion
of
the
memory
is
erased. Only
about
one third
of
the system's
memory
is
"permanent,"
but
this portion
is
reserved for the use
of
the computer. This situation requires the use
of
diskettes
to
establish a stable means
of
storing information.
The Macintosh
is
designed
to
operate with a custom ver-
sion
of
the Sony
31h
inch diskette. Each diskette
is
housed
within a hard plastic covering. The disk drive records as well as
reads information from the surface
of
the diskette. These types
of
diskettes differ from the more commonly used "floppy
disks"
in three
major
ways. First
of
all, Mac diskettes are more
efficient since they offer more
than
twice the
data
storage
on
a
smaller surface. Also, the plastic cover
on
Mac diskettes makes
them more durable. Finally,
Mac
diskettes are more accurate
because they have a metal center
that
allows the drive
to
hold
the diskettes securely. Each diskette
is
capable
of
storing
about
enough information to fill
150
double spaced, typed pages.
Since the disks are essentially a magnetic means
of
record-
ing information, disks can be erased by magnetic fields. There-
fore, diskettes should always be stored in a safe place. Virtually
all electrical equipment (including the Mac) generates stray
magnetic fields. Therefore, never keep diskettes near electrical
appliances
or
telephones.
The durable construction
of
the Mac's disks makes
them
very reliable. They can be handled, dropped,
or
written
upon
without harming the magnetic medium within. At some point
during normal operation, you may find
that
the Mac will not
accept a certain disk. This
sort
of
error
is
usually referred
to
as
a system
error
and
requires
that
the system
be
restarted. This
problem
is
most likely not due
to
a physical defect in the disk.
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