In the case of the 5.25 inch flexible disc, the write protection device is a
slot cut in the edge of the protective jacket which can be covered by
small stickers provided with each pack of discs.
Disc files and directories
Everything you store on a disc (information, p r o g r a m s etc.) must be
given a n a m e which we c o m m o n l y refer to as a 'filename', hence the
t e r m 'Disc files'. Each time you store some data in a new file, the
filename, together with the location of the first sector of data, is written
onto a specially reserved sector called a directory. T h e system allocates
a directory sector for every fifteen filenames you create, for example, if
you stored data in a total of 60 different files, four directories would be
created. The directory m a k e s it easy for the read/write heads to quickly
locate a piece of information, and most systems have a facility which
enables you to display the contents of directories to find out exactly
which files are on a disc.
In addition to a list of filenames, each directory, when it holds the
m a x i m u m of fifteen filenames, also holds the sector location of the next
directory.
Figure 2 shows both types of disc with the write protect devices.
Formatting the Disc
Before a disc can be used for storing data it must be put through a
process called
formatting.
As we explained previously, a disc is divided
into a n u m b e r of tracks and a n u m b e r of sectors per track. W h e n a disc
is
formatted
the beginning of each and every sector is m a r k e d so that the
system can recognise it.
In addition to sector marking, formatting has two m o r e important uses:
It enables you to give the disc a n a m e and it reserves a 'system' sector on
track 0 for the storing of certain essential information about the disc
itself. For the m o r e technically minded user, here is a list of items stored
in the O R I C microdisc system sector:
- - T h e
n a m e of the disc (this is the name you gave it during
formatting)
- - The version n u m b e r of the disc operating system under which the
disc was created ( f o r m a t t e d )
- - T h e n u m b e r of sectors currently full of stored data (excluding
directories)
