User`s guide
FORMAT
When to Format a Device
Formatting is advisable under the following circumstances:
• When you receive a new RK05 disk from Digital.
• When you wish to format an RX02 double-density diskette to single density and
vice versa.
• When you wish to eliminate bad blocks (though formatting does not guarantee
the elimination of every bad block, formatting can reduce the number of bad
blocks).
What the FORMAT Verification Procedure Does
When RT–11 verifies a volume, it writes a 16-bit pattern in each word on each block
in the volume and then reads each pattern. When RT–11 is unable to write and
read a pattern, it reports a bad block. The verification process is similar to the bad-
block scan (see INITIALIZE), except that verification is a data-destructive process.
That is, whereas bad-block scanning only reads data from each block on a volume,
verifying both writes and reads data, destroying any data previously existing on the
volume.
Because the verification process reads and writes data, it can be more effective than
a bad-block scan in establishing the validity of data contained in a block. Verifying
also makes sure that the previous formatting operation was successful.
Confirming Your FORMAT Request
When you issue the FORMAT command, RT–11 displays the prompt:
<dev:>/FORMAT-Are you sure?
The variable <dev:> represents the drive name and unit number of the volume you
want to format. Type Y
RETURN
to continue the format operation. Type N
RETURN
or press
CTRL/C
to abort the operation.
Formatting RX01 and RX02 Diskettes
You can format an RX01 or an RX02 diskette only when you have mounted the
diskette in a double-density diskette drive unit (RX02). Unless you use the
/SINGLEDENSITY option, RT–11 formats diskettes in double-density format. If you
attempt to format a diskette in a single-density drive unit (RX01), RT–11 displays
an error message.
Formatting RK06 and RK07 Disks
When you format an RK06 or RK07 disk, RT–11 lists the block numbers of all the
bad blocks in the manufacturer’s bad-block table and in the software bad-block table.
124 RT–11 Command Descriptions