Information recording disc and system

An information recording disc having at least two bands of information provided thereon. Each of the bands contain at least one track with one of the at least two bands being a read-only area band or a write area band along the one track of the one band. Another of the at least two bands is a mixed area band having at least one read-only area and at least one write area at different portions along the track of the mixed area band. An information system utilizes the disc for writing and reading information to and from the disc.

BACKGROUND OF THE INVENTION 
The present invention relates to an information recording disc implemented 
as a disc type recording medium and, more particularly, to an information 
recording disc adapted to handle efficiently both large amounts of 
previously recorded data and additional information recorded thereon by a 
user. 
One representative type of conventional optical disc is a CD-ROM (compact 
disc read only memory), which is a disc type recording medium. This type 
of disc is manufactured as follows: While an original disc is being cut, 
data signals are recorded thereon by use of a pit pattern of tiny bumps 
and dents. When finished, the original disc is copied so as to produce at 
low cost large quantities of optical discs containing the same data. 
Recent developments in this field include writable optical discs whose 
contents may be deleted or overwritten with new data. 
Where optical discs are used as the medium for providing users with 
programs or data, it takes too much time and cost to record the data on 
each disc one at a time for the individual users. Meanwhile, it is not a 
good practice of maintaining software resources if the user is to use and 
handle two discs separately: one being an optical disc cut from the 
original disc and containing the prerecorded program and/or data, and the 
other an optical disc on which the user records his own information. 
One solution to the above dual disc disadvantage is proposed in Japanese 
Patent Laid-Open No. 62-173630. The disclosure envisages one optical disc 
comprising both read-only prerecorded data areas and data write areas, the 
latter being the domain in which the user may write his own data. 
On the above optical disc, data is prerecorded on the read-only areas using 
the pit pattern of tiny bumps and dents when the disc is cut from its 
original. This prior art method of recording data makes it easier to copy 
optical discs containing data. The method also allows the user to record 
his own data onto the data write areas on the disc. Thus the time and the 
cost required for manufacture of the optical discs are reduced, and the 
discs produced in this manner are easy to maintain. 
The above-described conventional optical disc has inner and outer 
concentric band type areas on the surface thereof. The inner areas are the 
read-only prerecorded data areas (ROM), and the outer areas are the data 
write areas (RAM) to which data may be added later. When writing and 
reading data to and from this optical disc, the system must use the 
predetermined read-only and data write areas. Thus, it is difficult to use 
one optical disc for different purposes depending on application programs. 
Further, where an application program handles large amounts of data, it is 
important to improve the throughput or the optical disc system. With the 
prior art disc, however, it takes time to move the pickup over the surface 
thereof for access to data. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide an 
information recording disc having a mixed area band including at least one 
read-only area and at least one write area located close to one other 
thereon along a track of the band, the read-only area containing a large 
amount of prerecorded data, and the write areas containing user-input 
data, the division status of these areas being minutely defined by area 
division control information for data control, wherein the system gains 
easy access to any of the data due to the reduced number of times it needs 
to gain access thereto. 
It is another object of the present invention to provide an information 
recording disc on which the area division control information is located 
close to the read-only and/or write areas so that the time it takes the 
system to access any data is reduced. 
In carrying out the invention and according to one aspect therefor, there 
is provided an information recording disc comprising a mixed band area 
constituted by fan-shaped read-only areas having the same sector number in 
the radial direction and by fan-shaped write areas having a sector number 
different from that of the read-only areas. 
According to another aspect of the invention, the data prerecorded to the 
read-only areas uses a pit pattern. Further, the disc having the mixed 
area divided into a read-only area and a write area has the information 
about the disc division status written to an inner concentric portion 
thereof. Additionally, the disc has the information about the disc 
division status written to the beginning of an alternate write area of 
each band area thereof. 
According to a further aspect of the invention, there is provided an 
information recording disc containing as mixed area division information 
the number of the sector acting as the boundary between the read-only area 
and the write area within the mixed area. Further, the mixed area division 
information may be provided as a flag per track which shows each sector to 
be either the read-only area or the write area. 
According to another aspect of the invention, there is provided an 
information recording disc having each of the band areas thereof assigned 
an attribute, the attribute of a given band area showing that band area to 
comprise both a read-only area and an additional write area. 
According to the present invention, when reading data from a recording 
medium, the system first gains access to inner tracks containing bad 
sector alternate information and band area division information. For a 
band area having a mixed area attribute, the division information is read 
from the specific location in which that information is written, at least 
before data starts being read from within that band area. Where the 
division information is located in the beginning of the alternate write 
area of each band area, that information is read along with the bad sector 
alternate information. Where the mixed area division information is 
recorded, no write operation is performed onto the read-only area. 
These and further objects, features and advantages of the present invention 
will become more obvious from the following description when taken in 
connection with the accompanying drawings which show for purposes of 
illustration only, several embodiments in accordance with the present 
invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawings, FIGS. 1(A)-1(C) are views showing how an 
information recording disc 10 is divided in accordance with the present 
invention and has data written to the divided areas thereof, while FIG. 2 
is a block diagram of a system utilizing such an information recording 
disc. In FIG. 2, a host system 20 includes application programs or 
software 21 and a disc driver software 22 constituting a software portion, 
while a hardware portion is constituted by a disc drive unit 23 and an 
optical information recording disc 10. Under control of the host system 
20, the disc drive unit 23 writes and reads data to and from the optical 
disc 10 and exchanges data with the disc driver software 22. The 
application software 21 may illustratively be an information retrieval and 
display program. The information contained on the optical disc 10 is 
accessed via the disc driver 22. 
As shown in FIG. 1(A), the optical disc 10 is divided into "n" (n: natural 
number) band-shaped areas (called band areas). Each band area is assigned 
to a read-only area, a write area or a read/write mixed area. A disc 
structure table 11 is located in the innermost concentric portion of the 
disc, the table containing the location, size and attribute of each of the 
band areas. 
In FIG. 1(A), the band areas are numbered 1 through "n" from the innermost 
concentric portion outward. An area 12 with band No. 1 is assigned as a 
read-only area (ROM), an area 13 with band No. n-1 is assigned as a write 
area (RAM), and an area 14 with band No. "n" is assigned as a mixed area 
(ROM and RAM). The mixed area is divided into a read-only area and a write 
area, with a sector acting as the boundary therebetween. 
FIG. 1(B) is a view depicting the contents of the disc structure table 11. 
The disc structure table 11 is written on track 0 (innermost track) and 
contains the location, size and attribute of each band area. According to 
FIG. 1(B), band area No. 1 begins on track 1, is 10 tracks wide, and has 
the attribute of a read-only area. 
FIG. 1(C) is a view illustrating how the first track of each area shown in 
FIG. 1(B) is divided. In FIG. 1(C), one track comprises "s"+1 sectors (s: 
natural number). As indicated, all sectors of band area No. 1 are assigned 
a read-only area; all sectors of band area No. n-1 are assigned a write 
area; and band area No. "n" is divided into a read-only area and a write 
area, with a sector acting as the boundary therebetween. 
One advantage of the optical disc 10 is that if a large capacity database 
is created in the read-only area of a read/write mixed area, with the 
reference history of or the related information on the database contained 
in the write area thereof, a database having a learning capability may be 
constructed through access to data within the same tracks. Another 
advantage is that each band area may be used for any of diverse purposes, 
with a data retrieval program held in the read-only area of each band area 
and the user data written in the write area thereof. 
A further advantage of the optical disc 10 is that an optical disc with its 
read-only areas formed using the pit pattern is conducive to having large 
quantities of copies thereof manufactured with ease, each copy containing 
large amounts of data. According to the invention, an application program 
and/or a database may be prerecorded on large quantities of discs, and the 
discs may be later customized by individual users adding their own data 
thereto. 
FIG. 3 is a set of views depicting how data is divided and recorded on an 
information recording disc according to another embodiment of the 
invention. FIG. 3(A) is a view showing the contents of a disc structure 
table recorded on track 0. As shown in FIG. 3(A), the content of the 
record corresponding to each band area include, in addition to that shown 
in FIG. 1, information indicating the location of a read-only area. As 
depicted in FIG. 3(B), band area No. "n" indicates that nine sectors 
numbered 0 through 8 make up the read-only area and that the other sectors 
numbered 9 through s-1 constitute the write area. Given that sector 
configuration, the information on the read-only area location is given as 
0-8 as shown in FIG. 3(A). 
As described, the innermost concentric portion of the same medium contains 
the information about how read-only and write areas are divided. Having 
the disc drive unit reference this information protects the data in the 
read-only area from being destroyed by unauthorized access from an 
application program. 
With the disc structure table located in the innermost concentric portion 
of the disc, the optical pickup device is allowed to start acquiring the 
band area division information and read/write mixed area information 
immediately after returning to its home position in the innermost portion 
of the disc. 
FIG. 4 is a set of views illustrating how data is divided and recorded on 
an information recording disc according to a further embodiment of the 
invention. FIG. 4(A) shows the contents of a disc structure table recorded 
on track 0. In FIG. 4(A), the contents of the record corresponding to each 
band area include, in addition to that shown in FIG. 1, the information 
indicating the location of a read-only area. As depicted in FIG. 4(B), 
band area No. "n" indicates that four sectors numbered 0 through 3 make up 
a read-only area, another four sectors numbered 4 through 7 constitute a 
write area, another four sectors numbered 8 through 11 represent another 
read-only area, and so on. That is, the sectors are divided in units of 
four to form alternated read-only areas and write areas four sectors wide 
each. Given that sector configuration, the information about the read-only 
area locations is given as 1/0 sector attribute flags, as shown in FIG. 
4(A). When set to 0, a flag indicates a read-only area; when set to 1, the 
flag denotes a write area. 
As a result, the effects of the invention described in connection with FIG. 
3 are supplemented by the ability to divide read/write mixed band areas as 
desired according to the application program or the database structure. 
As one variation of the above-mentioned embodiment, the mixed area 
information and the band division information need not be contained 
together in the disc structure table. As long as the two kinds of 
information are located close enough to each other, the advantage of data 
retrieval without track access remains unchanged. As another variation, 
the disc structure table may be located close to the home position of the 
optical pickup device, regardless of the home position being in the 
innermost or outermost concentric portion of the disc. As long as the 
pickup device has its home position located close to the disc structure 
table, the advantage of acquiring data of that table without track access 
remains unchanged. As a further variation, either the disc drive unit or 
the disc driver program may take on the task of controlling band area 
division information or of protecting read-only areas from data 
destruction. This is possible as long as the information control or data 
protection feature thus provided remains the same from the viewpoint of 
the application program in question. 
FIG. 5 is a set of views depicting how data is divided and recorded on an 
information recording disc according to another embodiment of the 
invention. FIG. 5(A) shows the contents of the record with band area No. 
"n" in the disc structure table recorded on track 0. In FIG. 5(A), the 
record contents include a band starting track number, an intra-band user 
area track count and an alternate area track count. To band area No. "n", 
as shown in FIG. 5(B), are assigned 990 tracks which are numbered 14,000 
through 14,989 and which constitute a read/write mixed user area, and 10 
tracks which are numbered 14,990 through 14,999 and which make up an 
alternate area. The starting track of the alternate area (track No. 
14,990) contains read/write mixed area division information; the remaining 
tracks (Nos. 14,991-14,999) retain alternate area information. The 
division information was described earlier and any repetitive description 
thereof will be omitted. As described, the starting track number is 
14,000, the intra-band user area track count is 990, and the alternate 
area track count is 10, all recorded as shown in FIG. 5(A). 
If any error is detected in the data written in a band area, the disc drive 
unit writes correct data in an alternate area for recovery from the bad 
sector. If the application program requests recovery from a bad sector, 
the disc drive unit must read the corresponding alternate area 
information. In that case, the disc drive unit needs to acquire beforehand 
the alternate area information on each band area. If the division 
information is located close to the alternate area information (in FIG. 5, 
on the starting track of the alternate area), the two kinds of information 
may be read without track access. 
With the above embodiment, the division information is recorded on the 
starting track of the alternate area. Alternatively, the division 
information may be located in the starting sector and the effects of the 
invention still remain the same. 
FIG. 6 is a set of views showing how data is divided and recorded on an 
information recording disc according to still another embodiment of the 
invention. FIG. 6(A) illustrates the contents of the record with band area 
No. "n" in the disc structure table, along with the recording status of 
track 14,000 which is the starting track of band area No. "n". First, the 
sectors numbered 0 through 3 constitute a read-only area. A flag set to 1 
is attached as a sector attribute flag to each of the first four sectors 
(the flags identifying the read-only area). A band attribute is also 
provided, indicating a read/write mixed area. 
FIG. 6(B) depicts how data is added to the write area shown in FIG. 6(A). 
As indicated, the data added to the sectors 4 through 7 sets the 
corresponding sector attribute flags to 1 each. Thus, these sectors are 
turned into an additional read-only area and in this manner, the 
information recorded later is protected from destruction by write 
operations that may be attempted by the application program. 
FIG. 6(C) illustrates how the data having been written as shown in FIG. 
6(B) is subjected to subsequent processing. As shown in FIG. 6(C), the 
band attribute is changed to indicate a read/write mixed area indicated as 
read/re-write. This makes it possible to write or change data, as needed, 
in the sectors numbered 8 through s-1 
FIG. 7 is a view showing how a database is illustratively constructed 
according to the invention. The database of FIG. 7 is basically a map 
database supplemented by diverse kinds of information. With reference to 
FIG. 7, the read-only areas on the optical disc constitute a ROM (read 
only memory) formed using a pit pattern; the write areas make up an MO 
(magneto-optical) memory in which data may be recorded or altered in a 
magneto-optical manner. 
First, a source vendor records blank map information into a read-only area. 
At this point, as shown in FIG. 6(A), the band attribute identifying a 
read/write mixed area is provided; the blank map information is given a 
read-only area flag. 
Next, a value added re-selling (VAR) vendor adds traffic information to the 
blank map information provided on the disc by the source vendor. As 
depicted in FIG. 6(C), the MO area to which the information was added is 
turned into a ROM before the disc is returned to the user. 
The map database thus offered is later supplemented by the individual user 
adding such incidental information as user branch-related information, 
branch names, branch sales and others. The user-added information may be 
altered as needed. 
The map database thus constructed allows traffic information, branch 
network information and other information to overlap with the blank map 
when reproduced on a display unit. Because the information added to the 
blank map is located on or close to the tracks containing the blank map 
information, the efficiency of data retrieval is enhanced. 
FIG. 8 is a set of views depicting how data is divided and recorded in 
units of tracks on an information recording disc according to a further 
embodiment of the invention. FIG. 8(A) shows the contents of the record 
with band area No. "n" in the disc structure table, along with the 
recording status of track 14,000 which is the starting track or band area 
No. "n". First, the sectors numbered 0 through 3 constitute a read-only 
area. The sector attribute flags of the first four sectors are set to 1 
each (the flags identifying the read-only area). The flags are recorded in 
an initial value recording area formed using a pit pattern. A band area 
attribute identifying a read/write mixed area is provided. Where the disc 
of FIG. 8 is to be read, the division information written in the initial 
value recording area is referenced because no track division information 
is recorded in a changed value recording area. 
FIG. 8(B) illustrates recording status in which information is added to the 
write area of FIG. 8(A). As indicated, the data written to the sectors 
numbered 4 through 8 causes the corresponding sector attribute flags to be 
set to 1. The changed flags are written in the changed value recording 
area. The sectors are then included in the read-only area. Where the disc 
of FIG. 8(B) is to be read, the track division information contained in 
the changed value recording area is referenced, and the division 
information held in the initial value recording area is ignored. As a 
result, the subsequently added information is protected against 
destruction by write operations that may be attempted by the application 
program. 
The above-described arrangement allows the track division information to be 
formed beforehand using the pit pattern. This makes it easy to copy discs 
containing read/write mixed areas. When user data is added to the write 
areas, the track division information may be changed accordingly. 
The embodiments mentioned above are optical discs having their surfaces 
formed using pit patterns of bumps and dents. Alternatively, magnetic disc 
media may be utilized and still the advantage of an enhanced track access 
speed in reading and writing information remains the same as long as the 
media contain prerecorded data. 
There may exist on the recording medium one or multiple read/write mixed 
band areas and the effects of the invention remain the same. 
Where the host system is to write or read information to or from an optical 
disc formed according to the invention, the disc is divided into 
appropriate areas in accordance with the purpose of the application 
program in question. In this manner, both the read-only and the write 
areas may be used as needed on the disc. 
With the mixed area division information located close to such disc 
structure description information as band division information and bad 
sector alternate information, a read-only area may be separated from a 
write area without resorting to the timing-consuming track access. 
Since data may be prerecorded in read-only areas using the pit pattern, it 
is easy to copy optical discs containing large amounts of data. 
The division information comprises flags identifying the read-only and 
write areas of the applicable tracks. This arrangement inhibits 
inadvertent overwrite operations onto any prerecorded read-only area, and 
permits the choice of a large capacity disc memory for user-specific 
usage. 
As described, the read-only and write areas located close to one another 
make it possible to reduce the number of times large amounts of data are 
accessed for update. The division information for controlling the area 
configuration is minutely defined so that relevant control information is 
acquired before the host system gains access to data. This boosts the 
throughput available when the application program handles large amounts of 
data on disc. Because the division control information is located close to 
the read-only and write areas, the access time required to get the 
information is also reduced. 
While we have shown and described several embodiments in accordance with 
the present invention, it is understood that the same is not limited 
thereto but is susceptible of numerous changes and modifications as known 
to those skilled in the art and we therefore do not wish to be limited to 
the details shown and described herein but intend to cover all such 
changes and modifications as are encompassed by the scope of the appended 
claims.