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Commodore 64 Scene Diskmags Assortment
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Escape_1_Nov._Edition_1989-11-18_-.d64
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2023-02-26
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T R A C K 1 8
****************
Track 18 is for Commodore 1540/1541
diskdrive users a very interesting
track.
In this track all the important data
are stored which are used by the drive
for reading or writing files to the
disk.
For example in track 18 are stored
the BAM (which registrates the free
blocks !!!) and the DIRECTORY !!!
It is possible to manipulate this
track trough which you can get special
effects !!!!
It's important to know that each
track, and there are 35, has been
seperated in some sectors.
Every sector exists of 256 bytes.
Byte 0 en 1 are used by the drive.
Bytes 2-255 are free for data.
In fact there are some extra bytes
for example : the checksum ..
But we won't bother you with that !!!
Track 18 has got 19 sectors, numbered
from 0 up to 18. They are used like
this :
Track 18 Sector 0
BAM & Directory Header.
-->
Byte(s) contains description
*****************************
0-1 18-01 Track, sector of the
the following block.
2 65 A, the format (4040)
3 0 Future expansion
4-143 ? BAM, keeps a record
of used/free blocks
144-161 ? Disk name (16 char.)
filled up with shift-
space.
162-163 ? Diskette ID (2 pos.)
164 160 Shift-Space
165-166 50,65 2A, DOS version
167-170 160 Shift-Space
171-255 0 Unused
Track 18 Sector 1 to 18. the Directory.
***************************************
Byte(s) contains description.
******************************
0-1 18-? Track and sector
following block.
2-31 ? File name 1
34-63 ? File name 2
66-95 ? File name 3
98-127 ? File name 4
130-159 ? File name 5
162-191 ? File name 6
194-223 ? File name 7
226-255 ? File name 8
So, there are 18 blocks and in all
of them can be stored 8 filenames.
18 times 8 makes 144 files.
The missing bytes are not used.
Every group of 30 bytes are organised
like this :
Byte(s) contains description
*****************************
0 128+? Filetype
0-DEL, 1-SEQ, 2-PRG,
3-USR and 4-REL.
1-2 ?-? Track and sector o/t
first sector o/t file
3-18 ? File name filled
with Shift-Space.
19-21 ? reservated for REL
files. see manual.
22-25 ? Unused.
26-27 ?-? Only used with '@0'
28-29 X-Y Size of the file.
X+(Y*255).
To change something we need a disk
monitor!!!
I use DISKDOCTER .It's public
domain ,only 13 blocks and it's easy
to use !!!
look for further information in the
following short manual .
D I S K D O C T E R
*******************
After booting it it will ask you
to place the desired disk in the drive
and to press a key. You wil now see
a screen in which you can give the
desired track and sector.
Normally this will be track 18,
sector 0 !!!!
After you made your choise you can
split the screen in 3 parts.
the header
**********
In the upper left corner you will see
the name of the programmer.
Right next to it there is written which
drive you use and the DOS version.
The upper right corner tells you the
actual track and sector.
In the leftbottom you'll see the
place-number o/t cursor.
Next to it are the decimal ,hexa-
decimal and ascii values o/t byte
under the cursor.
Next to that is the orginal ID with
which the disk has been formatted in
dec. , hex. and ascii values.
In the right bottom are the track
and sector to which the the drive will
go shown. We call this the 'LINK'.
The middle part
***************
In this you can see 256 bytes what
makes a complete block.
You can change the bytes!!!
the bottom piece
****************
The insructions you can use are written
in here !!!!
B = choose a new Track and Sector.
+ = next Sector (sector=sector+1).
- = previous Sector (sector=sector-1).
@ = change the value of the byte
under the cursor.
P = get orginal ID (not nessecary)
L = next sector (follow the link).
R = write block to disk (with the
changes)
T = Type a text from the cursor pos.
RETURN = end.
Q = quit the programm.
-->
T R I C K ' S
*************
Use, if you try this tricks, an old
disk. Format this disk and look at it
(in the disk-monitor of course ..). Then save some programms on it and try
the following tricks.
Track 18 Sector 0 Byte 2
****************************
this adres contains a 'A'. If you
change it in a 'B' you can't save
anything anymore on your disk.
A nice protection for your disks!!!
Track 18 Sector 1-18 Byte 0 & 1
**********************************
If you change the link bytes of the
last directory sector so that they
point to the first DIRECTORY sector.
You'll get a never ending DIRECTORY!!
Track 18 Sector 0 Byte 171-255
**********************************
You can place some text in these bytes.
'cause the drive doesn't use them!!
Track 18 Sector 0 Byte 144-166
**********************************
These adresses are containing the
diskname,ID and DOS-type.
You can change these
into whatever you want!!!
Track 18 Sector 1-18 Filenames
*********************************
If there's free space you can type
behind a filename ',8' or ',8,1:' but
you have to skip one shift-space.
If you don't skip a shift-space the
extra entered text will stand between
the quotation marks (your filename
will be larger).
Track 18 Sector 1-18
**********************
You can also put a special sign (like
a color or a clr-home) for your
filename. When you load
this file the sign will be executed.
First type the sign and then
the filename ,it doesn't matter if you
seperate them by a shift-space.
Track 18 Sector 1-18
**********************
In byte 28 and 29 o/t filename you can
simply change the blocks o/t file.
You can change them into a value
between 0 and 65525.
Byte 29 is the size from 0 to 255
blocks, byte 28 is the value times 256
Track 18 Sector 1-18
**********************
Byte 0 o/t filename contains the type
o/t file. You can change these types.
You can also get back a lost file by
changing his type !!!!