Commodore 1551 User Manual page 23

Starting with the top line, here is what it tells us:
The 0 at the left end tells us that the 1551's single drive is drive O. If we had gotten
this directory from a dual disk drive, it might have said" I" instead. The next thing on the
top line of the directory is the name of the diskette, enclosed in quotation marks, and
printed in reverse field. Just as each program has a name, so does the diskette itself,
assigned when the diskette was formatted. The diskette name may be up to 16 characters
long, and serves mainly to help you organize your diskette library. The two character code
to the right of the name is the diskette ID, also created when the diskette was formatted,
and equally useful for individualizing diskettes.
The 2A at the right end of the top line tells us that the 1551 uses version 2 of
Commodore's DOS (disk operating system), and that it, like most Commodore drives,
uses format "A."
The rest of the directory contains one line per program or file, each line supplying
three pieces of information about its subject.
At the left end of each line is the size of that line's file in blocks (or sectors) of 256
characters. Four blocks are equivalent to I K (1024 characters) of RAM (read/write)
memory inside the computer.
The middle of each directory line contains the name of the fi Ie, enclosed in quotation
marks. All characters between the quote marks are part of the name, and must be included
when loading or opening that file.
The right portion of each directory line is a three character abbreviation for the file
type of that entry. As we will see in later chapters, there are many ways to store
information on a diskette, most of which are associated with a distinctive file type.
TYPES OF FILES A V AILABLE
Currently used file types include:
PRG
=
Program files
SEQ
=
Sequential data files
REL
=
Relative data files
USR
='
User (nearly identical to sequential)
DEL = Deleted (you may never sec one of these.)
(Note: Direct Access files, also called Random files, do not automatically appear in
the directory. They are discussed in Chapter
7.)
After all the directory entries have listed, the directory finishes with a message
showing how many blocks of the diskette are still available for use. This number can vary
from 664 on a new diskette to 0 on one that is already completely full.
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