An operating portion is included in an input/output section of an information read/write device. The operating portion judges whether or not a sector is usable on the basis of medium position information and record position information. A device information storing portion is inserted between a read/write portion and a communication portion. Memory capacity of the device information storing portion is equal to or larger than a data read/write unit. Read/write information on the recording medium is temporarily developed into the device information storing portion, so that information is transferred in blocks of read/write unit that can be handled in an OS.

BACKGROUND OF THE INVENTION 
The present invention relates to a method and a device for preprocessing a 
writable recording medium of a large memory capacity such as an optical 
disc, and for writing information into and reading information out of the 
recording medium. 
Recently, a CD-ROM (compact disc--read only memory) is widely used as an 
information read-out device. The CD-ROM, based on the technique of CD-DA 
(compact disc--digital audio), has advantageous features of large memory 
capacity and low cost. Because of these features, software suppliers use 
the CD-ROMs as media most suitable for supplying application programs to a 
great number of users. The CD-ROM has only the read or reproduction 
function for users. Accordingly, to record information, another 
information read/write device must be used. For this reason, great efforts 
have been made to develop devices capable of recording or writing a great 
amount of information into and reproducing or reading the information from 
the disc. There are a CD-WO (compact disc--write once) and a CD-MO 
(compact disc--magneto optics), standardized under a standard book, called 
an orange book. The former is of the worm type, and already marketed. The 
latter is of the rewritable type, and at a stage just before its practical 
use. 
It is a common practice that information is coded in a state that an error 
correction code is attached to the information before the information is 
recorded into the recording media, such as CDs. A cross interleaved 
reed-Solomon code (CIRC), a kind of the error correction code, includes a 
reed-Solomon code having an excellent ability to correct minute defects 
(referred to as a random error) of 1 or 2 bits caused in the disc 
manufacturing stage, and means for converting a burst error to the random 
error by dispersing, under predetermined rules, data, called interleaved 
data, having an excellent ability to suppress defects (referred to as a 
burst error) continuing for a relatively long time, caused by dust, flaws 
on the disc and by a disturbance in the control device. 
A read/write information unit conversion method is disclosed in Unexamined 
Japanese Patent Publication No. Sho. 63-81661. In this publication, the 
number of the medium read/write units are selected to be equal to the 
number of sectors per track (one turn of the recording medium) on the 
recording medium. With this, a turn wait time present before information 
is transferred to and from the recording medium is eliminated. And the 
execution time of the read/write is reduced. 
In a conventional read/write device, such as a magnetic disc device, or a 
magneto-optical disc device, when a recording medium having no information 
recorded therein is used, the following procedural work is performed. When 
medium position information is correctly read out of the recording medium, 
and it is the medium position information that can be predicted on the 
basis of the previous medium position information, arbitrary information 
is written into the sector containing the medium position information. 
Then, the information is read out of the sector. If the information before 
written is coincident with the read out information, it is judged that the 
sector is usable. When the read out medium position information contains 
an error or when the information before written is not coincident with the 
read out information, it is judged that the sector is defective and 
unusable. The judgment is registered in the recording medium. In this 
case, a substitutive sector, in place of the defective sector, is also 
registered, thereby keeping the continuity in the array of the sectors on 
the recording medium (This work will be referred to as a "certify"). The 
"certify" process must be applied to over the entire surface of the 
recording medium used. Much time is consumed for the "certify" process. 
This "certify" process must be carried out within a limited time by users, 
and is an annoying and to-be-avoided work for users. 
When the "certify" process is applied to the information read/write device, 
such as a rewritable CD-MO using the CIRC, and a defect on the recording 
medium is found, not only the sector containing the defect but also a 
cluster (a group of sectors, and an information read/write unit in the 
read/write device) including the defective sector must be removed. Thus, 
where the large cluster size is used, a remarkable loss of the memory 
capacity is caused. 
The read/write information unit conversion method disclosed in Unexamined 
Japanese Patent Publication No. Sho. 63-81661 is directed to the recording 
medium shaped like a disc. The turn wait time can be removed only when a 
recording medium having a constant number of sectors per one turn is used. 
In other words, the read/write speed of data can be improved only for such 
a recording medium. However, in the case of the rewritable CDs, it is 
desirable to transfer data to and from the recording medium in blocks of 
the cluster. From the view that the read/write unit of the OS is 
approximately one sector, this read/write unit difference problem must be 
solved. 
SUMMARY OF THE INVENTION 
Accordingly, an object of the present invention is to provide a processing 
method and a processing device which improve a read/write processing speed 
for a recording medium of large memory capacity, particularly a rewritable 
CD, thereby providing a flexible read/write operation. Another object of 
the present invention is to provide a processing method and a processing 
device which lessen a load to users by eliminating the "certify" process 
consuming much time. Yet another object of the present invention is to 
provide a processing method and a processing device which judge whether or 
not a sector is usable before data record, and minimizes a loss of the 
memory capacity of the recording medium. Still another object of the 
present invention is to provide a processing method and a processing 
device which can reliably transfer data, even in a small read/write unit 
used in an OS, for example, to and from a recording medium of a large 
read/write unit. A further object of the present invention is to provide a 
processing method and a processing device which are suitable for the 
read/write operation for a recording medium of the large memory capacity. 
In the present invention, in judging whether or not a sector as a unit 
record area on a readable/writable recording medium is usable, the state 
of reading the record position information and the medium position 
information are checked. To be more specific, the following two steps are 
executed: a step for reading record position information written in a 
rewritable state into the sector, with a record position of information 
with an error correction code attached thereto; and a step for reading 
unprogrammable medium position information, formed in advance on the 
recording medium, for indicating a position of the sector. Then, it is 
judged whether or not the sector is usable on the basis of the state of 
reading the record position information and the state of reading the 
medium position information. The record position information and other 
information are written and read out in a state that a high error 
correction ability code, such as the cross interleaved reed-Solomon code, 
is attached to the information. Accordingly, if a sector has a minute 
defect, it is usable in a practical level. 
In the step for judging whether or not the sector is usable, it is judged 
that the sector is unusable when the record position information is 
abnormally read out, and the medium position information are abnormally 
read in succession. That is, it is judged that the sector is usable when 
the record position information is normally read out, and it is judged 
that the sector is usable when the number of the operations of abnormally 
reading the medium position information in succession is smaller than an 
integer n. On the other hand, it is judged that the sector is unusable 
when the number of the operations of abnormally reading the medium 
position information in succession is equal to or larger than an integer 
n. The integer n satisfies the following inequality (1). 
EQU {(defect factor).div.(number of sectors in one cluster)}&lt;(rate of 
occurrence of medium position information error).sup.n ( 1) 
In the inequality (1), 
defect factor=(unusable capacity by defect)/(total record capacity of 
record medium). The integer n is preferably the largest integer of those 
satisfying the inequality (1). 
Such a preprocessing can be carried out at high speed concurrently with 
reading information from the recording medium. Accordingly, in 
transferring data to and from the recording medium, it can be judged 
whether or not a sector is usable whenever occasion calls. Accordingly, 
there is no need of certifying the recording medium. Further, it is judged 
depending on a state of a sector just before information is recorded 
therein. Thus, the preprocessing of the present invention eliminates the 
"certify" processing for virginal recording media. Further, when 
information is actually recorded into the recording medium, it can be 
judged whether or not the sector is usable. Thus, a reliable recording of 
information into the recording medium is realized. 
The preprocessing method of the invention can be executed by an 
input/output device comprising: a read/write portion for inputting data to 
and outputting data from a readable/writable recording medium in blocks of 
the sector as a unit recording area; a code modulating portion for coding 
and decoding the data; and an operating portion for judging whether or not 
the sector is usable depending on a state of medium position information 
indicative of a position of the sector, which is written in advance in the 
recording medium and unprogrammable and is obtained through the read/write 
portion, and a state of record position information, which is rewritable 
into the sector and is obtained through the code modulating portion. When 
the recording medium is a rewritable optical recording medium, the medium 
position information is an absolute time in pregroove, and the record 
position information is any of data within the subcode. The number of the 
operations of abnormally reading the medium position information in 
succession is counted by the operating portion. When a count is equal to 
or larger than the integer n, it is judged that the sector is unusable. 
When data that is scrambled so as to convert a burst error into a random 
error, is written into and read out of a recording medium, the first 
read/write unit for the data transfer to and from the recording medium is 
considerably larger than the second read/write unit of the read/write 
information of an OS. Accordingly, it is desirable that information is 
written into and/or read out of the recording medium in blocks of the 
second read/write unit smaller than the first read/write unit by using an 
information storing portion capable of temporarily storing information and 
having the memory capacity at least equal to the first read/write unit. In 
the information read/write method, when information is read out of the 
recording medium, the following two steps are executed: a step for reading 
out of the recording medium first read/write information which consists of 
the first read/write unit including a record area corresponding to second 
read/write information consisting of the second read/write unit, in blocks 
of at least one first read/write unit, and for developing the read out 
first read/write information into the information storing portion; and a 
step for reading out of the recording medium the second read/write 
information of the first read/write information developed into the 
information storing portion, in blocks of the second read/write unit. When 
information is written into the recording medium, the information 
read/write method comprises: the above-mentioned reading steps; a step for 
replacing the second read/write information with a location corresponding 
to the first read/write information developed into the information storing 
portion; and a step for recording the first read/write information of the 
information storing portion into the recording medium in blocks of the 
first read/write unit. In this case, the recording step is executed at a 
given timing after the replacing step is executed several times when 
information is written into the recording medium. If so done, the number 
of operations to access the recording medium is reduced, thereby realizing 
an efficient and high speed processing. 
Such a processing is preferably executed by an input/output device 
comprising: a first input/output portion for transferring first read/write 
information with at least one first information read/write unit to and 
from the recording medium; a second input/output portion for transferring 
second read/write information with at least one second information 
read/write unit smaller than the first information read/write unit to and 
from the recording medium; and an information storing portion having the 
memory capacity at least equal to the first read/write unit and capable of 
temporarily storing information, the information storing portion 
preferably allowing the first read/write information to be transferred in 
blocks of the second read/write unit between the first input/output 
portion and the second input/output portion. When the input/output device 
is incorporated into the information read/write device, the first 
input/output portion serves as a read/write portion for transferring the 
first read/write information to and from the recording medium, and the 
second input/output portion serves as a communication portion for 
inputting and outputting the second read/write information through a bus. 
Further, if a code modulating portion for coding and decoding information, 
from the information storing portion, to be inputted to and outputted from 
the first input/output portion, is further included, a reliability of the 
input/output information is further improved. For example, information can 
be coded by the cross interleaved reed-Solomon code, and decoded. 
When the input/output device is provided in an information processor, such 
as a host computer, an external storage device containing the recording 
medium is used through the input/output device, the first input/output 
portion allows first read/write information to be inputted thereto and 
outputted therefrom through a bus, and the second input/output portion 
transfers the second read/write information to and from an operating 
system. In many computers, the first and second input/output portions may 
be realized in the form of a device driver operating under control of an 
operating system (OS). 
If the first input/output portion outputs the first read/write information 
at a given timing, the access to the recording medium is efficiently done, 
improving a processing speed. An information handling end command of an 
operating system or a command to eject the recording medium may be used as 
the given timing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A write/read device using a rewritable CD as an information recording or 
storing medium and a computer using the read/write device as an external 
input/output device thereof will be described for explaining the present 
invention. 
Device Outline 
FIG. 1 shows an outline of the combination of an information read/write 
device 10 and a host computer 20. The information read/write device 10 
includes an input/output section 12, which accepts a CD as an information 
recording or storing medium 11, for inputting and outputting data to and 
from the information recording medium 11, and a medium control mechanism 
19 for controlling a rotation of the recording medium 11 and the operation 
of positioning an optical head. The host computer 20 contains an operating 
system (OS) 21 for operating the computer, a device driver 23 which 
receives data from the OS 21 and sends data to the information read/write 
device 10, to thereby to be able to control the information read/write 
device 10, a memory 22, such as a RAM, and an application 24 operating on 
the basis of the OS 21. The host computer 20 further includes a timer 25 
with a clock function. The device driver 23, the timer 25, and a 
device/driver information storing part 26 as a part of the memory 22 make 
up an input/output control portion 27 of the computer. The device driver 
used for the input/output generally functions as a buffer for the 
interaction between the file handled by the OS and the file handled by the 
information read/write device. It is a common practice that the 
specification of the device driver, when it is used, is different for each 
information read/write device. 
The host computer 20 and the information read/write device 10 are connected 
by means of a bus 30, for example, SCSI. The host computer 20 and the 
information read/write device 10 are provided with bus interfaces 19 and 
29, respectively. Data and control instructions are transferred between 
the host computer and the information read/write device, through these 
interfaces. The input/output section 12 contained in the information 
read/write device 10 includes a communication portion 13 which receives 
data through the medium control mechanism 19 from the computer and sends 
data to the computer, a device information storing portion 14 for 
temporarily storing data transferred through the communication portion 13, 
a code modulating portion 15 for coding and decoding the data transferred 
to and from the computer into the data transferred to and from the 
recording medium, a read/write portion 16 for writing the coded data into 
and read the same from the recording medium 11, an operating portion 17 
for determining the results of the certify, and a control portion 18 for 
controlling those portions. 
To write data into the recording medium, the following procedure is taken 
in the input/output section 12. Before-code-modulation data, which is 
edited or formed through the communication with the computer and stored in 
the device information storing portion 14, is coded and modulated into 
coded data using CIRC by the code modulating portion 15, the coded data 
are converted into read/write data through the read/write portion 16, and 
the read/write data are stored into the recording medium 11. To read data 
out of the recording medium, the reverse procedure is taken. The 
read/write data are read out of the recording medium 11, restored to the 
coded data through the read/write portion 16, the coded data are modulated 
and coded into the before-code-modulation data by the code modulating 
portion 15, and the result is sent to the host computer 20. 
Data Structure 
The structure of the read/write data to be written into and read out of the 
recording medium 11 will be described with reference to FIGS. 2(a) to 
2(f). As shown in FIG. 2(a), a memory area of the recording medium 11 is 
segmented into a plural number of segmental areas each having the unit of 
a cluster 61. In the recording medium 11, one cluster 61, inclusive of 
additional information described later, has the data size of 76K bytes. 
The clusters to be inputted to and outputted from the recording medium 
will be referred to as "physical clusters". As shown in FIG. 2(b), one 
physical cluster 61 contains a logical cluster 70 of 64K bytes, which 
consists of a plural number of sectors 71, before-data additional 
information 62 located preceding to the logical cluster 70, and after-data 
additional information 63 located succeeding to the logical cluster 70. 
The before-data additional information 62 consists of a Link1 sector 64, a 
RunIn1 sector 65, and a RunIn2 sector 66. The after-data additional 
information 63 consists of a RunOut1 sector 67, a RunOut2 sector 68, and a 
Link2 sector 69. The input/output section 12 stores the plural number of 
sectors 71 in the logical cluster 70 into the recording medium 11 by using 
read/write data, which is dispersed and arrayed (scrambled) in the memory 
area of two successive sectors. For this reason, the sectors for the 
scramble must be located before and after the logical cluster 70, and the 
physical cluster 61 including the RunIn1 sector 65, RunIn2 sector 66, 
RunOut1 sector 67, and RunOut2 sector 68 is used to perform input and 
output. The physical cluster 61 further includes the Link1 sector 64 and 
the Link2 sector 69 that are located before and after the cluster, in 
order to absorb a nonuniformity of the rotation speed of the recording 
medium 11 and a variation of the sector positions caused by jitter of the 
read/write portion. 
FIGS. 3(a) to 3(d) show diagrams showing how to scramble the information in 
the form of sectors. Assuming that one sector before the scramble is 
carried out, consists of 2352 bytes, the whole data before the scramble 
are arranged in the order of sectors m, m+1, m+2, m+3, . . . (see FIG. 
3(a). When the data are scrambled, the data of the sector m is dispersed 
into sectors m, m+1 and m+2 (see FIG. 3(b)). The data of the sector m+1 is 
dispersed into sectors m+1, m+2 and m+3 (see FIG. 3(c)). As a result, the 
sector m after the scramble contains data located at a position in the 
three sectors m, m-1 and m-2 of the whole data before the scramble (see 
FIG. 3(d)). The remaining sectors are scrambled in similar ways. As the 
result of scrambling the data in the sector, if a burst error extending 
over the sector is caused, all the information of the sector are not lost 
and there is a possibility that the error is removed by using the CIRC, 
for example. Therefore, a reliability of data to be written into and read 
out of the recording medium is remarkably improved. 
The inputting and outputting of the scrambled and recorded data to and from 
the recording medium is incomplete when only a sector of the scrambled 
data is inputted and outputted. To make the input and output of the 
scrambled data, the sector and the sectors before and after the sector as 
well must be inputted and outputted. The same thing is true for the 
sectors located at the ends of the logical cluster 70. To scramble the 
data at the ends of the logical cluster 70, the RunIn1 sector 65 and the 
RunIn2 sector 66, and the RunOut1 sector 67 and the RunOut2 sector 68 are 
required. Thus, the scramble technique can secure a reliability of data. A 
sector contains the information of the sectors before and after the 
sector. Accordingly, when a sector to be read out of the recording medium 
is a sector m, three sectors including the data of the sector m (i.e., 
sector m, sector m+1 and sector m+2) must be read out. Similarly, when a 
sector to be written is a sector m, three sectors including the data of 
the sector m (i.e., sector m, sector m+1 and sector m+2) must be written 
into the recording medium. As described above, the information of the 
sectors m-2, m-1 and m must be written for the sector m, and the 
information of the sectors m-1, m and m+1, for the sector m+1. 
Accordingly, in writing and reading data to and from the recording medium 
11, one sector as referred to above is handled as a data write unit or 
block, and it is desirable to write and read data in blocks of the data 
write unit. 
Returning to FIG. 2, the logical cluster 70 consists of a plural number of 
sectors 71. The sector 71 consists of 98 number of EFM frames 72, as shown 
in FIG. 2(c). Here, EFM is the abbreviation of eight to fourteen 
modulation (8-14 modulation), which is one of various modulations. In the 
EFM, data of 8 bits is converted into a data pattern of 14 bits. One group 
(EFM frame) 72 of the information modulated by the EFM, as shown in FIG. 
2(d), consists of a synchronizing signal 73 used for sampling, and a 
subcode 74, and a series of data 75 with parities 76 following the 
subcode. A group of 98 number of EFM frames 72 is handled as one unit (98 
EFM frames). This constitutes one sector. 
When the subcodes 74 of 98 number of the EFM frames 72 are combined, the 
whole subcode having the structure as shown in FIG. 2(e) is constructed. 
The subcode 74 consists of a control bit 75, an address bit 76, subcode 
data 77, and a CRC (cyclic redundancy check code; a cyclic code for 
detecting an error of the subcode data) 78. The subcode data 77, as shown 
in FIG. 2(f), consists of a track number 79, an index 80, a current 
position 81 in a track, 0 data 82, and an absolute position 83. An error 
detection of the subcode data 77 is performed by the CRC 78. Since the 
subcode data are dispersed into 98 number of the sectors 71, it can 
reliably be read out unless a considerably large burst error is caused. 
Processing by Information Read/Write Device 
FIG. 4 is a diagram showing processes executed by the information 
read/write device 10. At the time of writing data and reading data out of 
the recording medium, the information read/write device 10 executes a 
preprocess 101 and an input/output process 102 for writing data into and 
reading data out of the recording medium, and for reprogramming data 
stored in the recording medium. 
Preprocess 
This process eliminates the "certify", which is used in the information 
read/write device, such as a magnetic disk device and a magneto-optical 
disc. The conventional device carries out a process, called "certify". 
This process checks a virgin recording medium every sector as to if it is 
normal in the information read/write capability before information is 
first written into the recording medium. More exactly, in the certify 
process, it is read out medium position information on the recording 
medium, and is judged if the medium position information can exactly be 
read out, and if it can be predicted on the previous medium position 
information. Next, arbitrary information is written into the sector 
containing the medium position information, and the same is read out of 
the sector. When the written information is coincident with the read out 
information, it is determined that the sector is normal in the read/write 
capability. When the medium position information contains a read out error 
and/or when the written information is not coincident with the read out 
information, it is determined that the sector is defective. In this case, 
the defective sector is registered as a defective area in the recording 
medium, and at the same time, another sector in place of defective sector 
is registered. With this registering operation, the continuity of the 
sectors can be secured in the read/write of data even if the recording 
medium contains detective sectors. The "certify" process consumes much 
time since it must be applied to the entire surface of the recording 
medium used. When the "certify" process finds a defective sector on the 
recording medium, the defective sector and the whole cluster containing 
the defective sector as well must be removed. Therefore, where the cluster 
size is large, if a defective sector is found, the memory capacity of the 
recording medium is remarkably reduced. 
In the present embodiment, the information read/write device 10 shown in 
FIG. 1 concurrently carries out the preprocess 101 for finding defective 
sectors and the input/output process 102, as shown in FIG. 4. Accordingly, 
there is no need of the "certify" process. One can load a virgin recording 
medium into the information read/write device, and immediately write 
information into and read the same out of the recording medium. In order 
that the defective finding process may be carried out concurrently with 
the input/output process, the preprocess in the present embodiment is 
arranged such that the check of the defective sector is made on the basis 
of the presence or absence of record position information and a rate of an 
occurrence of a read-out error of the medium position information, whereby 
a state of the recording medium can be grasped reliably and for a short 
time. To be more specific, the input/output section 12 of the information 
read/write device 10 forcibly reads data from the recording medium 11 
through the read/write portion 16, and decodes the data by the code 
modulating portion 15. It is determined whether or not the record position 
information is present on the basis of any of the information indicative 
of the record position in the decoded subcode data 77. As described above, 
the subcode data 77 is dispersed into 98 number of the EFM frames, and the 
CRC is used for error detection. Therefore, the data can reliably be read 
out unless a considerably large burst error is caused. Since the data are 
necessarily contained in the EFM frames, if the memory area under check 
contains this record position information, it is determined that it is a 
memory area where information has already been stored, and the memory area 
may be used for the read/write of information. In the input/output section 
12 of the present embodiment, the operating portion 17 uses the absolute 
position 83 of the subcode data for determining the presence or absence of 
the record position information. If required, another position 
information, such as the track number 79 or the current position 81 in the 
track, may be used for the same purpose. Any other modulation than the EFM 
data may be used as a matter of course, and it is possible to check as to 
if the record position information is present or absent by using position 
information comparable with the subcode data. 
The medium position information is directly provided in the recording 
medium in order to indicate the current positions on the recording medium. 
In the present invention, an absolute time in pregroove (ATIP) in a 
pregroove shown in FIG. 5 is used for the medium position information. 
This information is separated by the read/write portion 16 which directly 
receives data from the recording medium 11, and supplied to the operating 
portion 17. The term "pregroove" means grooves 84, shaped like guide 
rails, previously cut in the surface of the recording medium 11. 
Information indicative of the positions of the grooves 84 on the recording 
medium 11 are written in the form of ATIP 85 in the grooves 84 during the 
processing of manufacturing the recording medium 11. No error correction 
is made on the ATIP 85. Therefore, the burst error, if present, leads to 
an error of information read out of the recording medium. One ATIP is 
recorded for one sector. While in this embodiment, the ATIP 85 is used for 
the medium position information, any other means than the ATIP 85, if it 
is previously written in the recording medium, may be used for the same 
purpose. Further, it is evident that the recording medium applicable to 
the present invention is not limited to the circular recording medium 
shown in FIG. 5. 
Before proceeding with description of the methods of operating the record 
position information and the medium position information, the relationship 
between the record position information and the medium position 
information will be described with reference to the following table. 
TABLE 1 
______________________________________ 
read state 
absolute 
record 
position 
position compa. of judgement 
infor. infor. present 
state of medium 
(ATIP) (subcode) 
invention 
certify 
______________________________________ 
recorded normal normal information 
information 
is readable 
is readable 
minute error normal information 
information 
fault occurs is readable 
is readable 
large error error information 
information 
fault occurs occurs is not is not 
readable 
readable 
not normal error information 
information 
recorded occurs is readable 
is readable 
minute error error save information 
fault occurs occurs is not 
readable 
large error error information 
information 
fault occurs occurs is not is not 
readable 
readable 
______________________________________ 
In preparing Table 1, two types of the recording media, one having 
information recorded or stored therein and the other having no information 
recorded or stored therein were used. The medium position information 
(ATIP) and the record position information (subcode) were written into 
these recording media. In the table, the states of writing information 
into the media and evaluations on the results of the writing by the 
present invention and by the "certify" process executed in the 
conventional information read/write device are comparatively tabulated. 
In a case where the preprocessing is applied to the recording medium having 
information stored therein in the information read/write device of the 
present embodiment, when a read error occurs in both the medium position 
information and the record position information, it is judged that 
information of the sector cannot be corrected and hence use of the sector 
is prohibited. When neither the medium position information or the record 
position information can be read out, it is judged that after information 
is stored, the recording medium has flaws formed in and dust attached to 
the surface thereof after information is stored or recorded therein, and 
as a result, a large defect exists in the recording medium. In this case, 
there is no assurance that when data are written thereinto, the written 
data can be read out in a normal state. The same thing is true for the 
"certify" processing when it is applied to the recording medium in the 
conventional information read/write device. In a case where the medium 
position information, when read out, contains an error, but the record 
position information, when read out, contains no error, a minute defect is 
present in the recording medium, but the stored data are normally read 
out. In this case, the preprocessing of the present embodiment and the 
conventional "certify" processing certify that it can be used for the 
read/write of data. 
When the preprocess of the information read/write device in the present 
embodiment is applied to the recording medium having no information 
written thereinto, a read error is contained in the read out record 
position information since the recording medium has no information written 
thereinto. Therefore, the recording medium having the medium position 
information written thereinto is used for checking it for the read/write 
of data. When the medium position information is incorrectly read out of a 
sector, the "certify" processing simply judges that a sector cannot be 
used for the read/write of data. In this case, as already referred to, not 
only the sector suffering from a defect but also the whole cluster 
including the defective sector must be removed. In a recording medium 
having a high rate of occurrence of medium position information error, 
which will be described later, a read error of the medium position 
information frequently occurs. Accordingly, in this recording medium, a 
memory area, which is judged to be a read/write impossible area, is 
extremely large. 
On the other hand, in the information read/write device of the present 
embodiment, only when a read error of the medium position information 
successively occurs a preset number of times in a sector on the recording 
medium, it is judge that the sector is unusable. With such a judgement, 
sectors containing minute defects are allowed to be used for the 
read/write of data. As seen from the judgement on the recording medium 
having information stored therein, the error correction ability of the 
record position information is considerably high. Further, the error 
correction is likewise applied to other data stored in the recording 
medium. Actually, it is possible to write data into the sector. Thus, the 
sectors containing minute defects are allowed to be used for the 
read/write of data. Further, the preprocess of the present embodiment 
specifies the sector suffering from an instable read/write of data, viz., 
the sector that may have a large defect, on the basis of the fact that a 
read error successively occurs in the medium position information. Also in 
the preprocess of the present embodiment, it is judged that such a sector, 
together with the cluster including the sector, is unusable, and another 
cluster is substituted for the cluster containing the defective sector. 
That is, the preprocess of the embodiment determines whether a sector is 
usable or unusable on the basis of the number of successive failures of 
reading the medium position information out of the sector of the recording 
medium. The number n (n: integer) of successive read failures is defined 
by the following inequality (1). 
EQU {(defect factor).div.(number of sectors in one cluster)}&lt;(rate of 
occurrence of medium position information error).sup.n (1) 
In the above inequality, the defect factor is a ratio of a memory capacity 
that can actually be used, viz., except the memory capacity lost by a 
defect, to the whole memory capacity of a recording medium. In the present 
embodiment, the defect factor is a ratio of unusable clusters to usable 
clusters on the recording medium since data are written and read out every 
cluster. Incidentally, even if only one defective sector is contained in a 
cluster, the defective-sector contained cluster is unusable. Usually, a 
media supplier determines the specifications of recording media. 
Accordingly, a defect factor specified by the media supplier may be used. 
The error occurrence rate of the medium position information is a ratio of 
the number of sectors in which a read error of the medium position 
information probably occurs, to the total number of the sectors on the 
recording medium. In this embodiment, the error occurrence rate is that of 
ATIP since ATIP is used for the medium position information, and is 
approximately 0.1. 
The inequality (1) is derived from the following basic idea. The defective 
sector is a memory area having large flaw or various flaws gathered 
therein. Because of this, the medium position information containing 
errors are successively read out of such a memory area. As a consequence, 
the number of successive read errors of the medium position information 
can be used for judging as to whether a sector is usable or unusable. 
The left side of the inequality (1) is the division of a defect factor by 
the number of sectors in one cluster, and hence describes a probability of 
the presence of defective sectors. The right side of the inequality (1) 
describes a probability that a read error of the medium position 
information successively occurs n times. Since the right side is larger 
than the left side in the inequality, if a sector in which medium position 
information causes successively the read out error n times, is recognized 
as a defective sector, the defective sector on the recording medium can be 
recognized without failure. 
It is most preferable to select the maximum value of those of n which 
satisfy the inequality (1) for the integer n. By so doing, a maximum 
memory area that can be used by a user is secured. Further, since the 
right side is larger than the left side in the inequality (1), there is 
prevented such an unwanted situation that a defect in a sector of the 
recording medium grows by oxidation with time to have a defect size large 
enough to damage the sector to such an extent that the sector cannot be 
used for the read/write of data. In other words, in the preprocess of the 
present embodiment, judgement as to whether or not a sector is defective 
is made at an early stage. It is evident that the maximum value of n 
satisfying the inequality (1) may be substituted by n of which the value 
is smaller than the maximum value. The value of n may be determined in 
consideration with a durability of the recording medium and ambient 
conditions where it is used. 
The integer n for different numbers of sectors in one cluster and defect 
factors is shown in Table 2. 
TABLE 2 
______________________________________ 
number of sectors 
defect in one cluster 
factor 4 8 16 32 
______________________________________ 
10% 64 MB 1 1 2 2 
5% 32 MB 1 2 2 2 
1% 6.4 MB 2 2 3 3 
0.5% 3.2 MB 2 3 3 3 
0.1% 0.6 MB 3 3 4 4 
______________________________________ 
defect capacity when total capacity of the recording medium is 640 MB 
For ease of explanation, Table 2 shows some specific values for several 
sectors in one cluster and defect factors. However, n can be calculated 
for other values. In an example where the number of sectors in one 
cluster=32 and the defect factor=1%, defect sector existence 
probability=3.125.times.10.sup.-4. This value is smaller than a 
probability that a read error of the medium position information 
successively occurs three times=1.times.10.sup.-3. Accordingly, if n=3, it 
exceeds an existence probability of the defective sector on the recording 
medium. Hence, the present invention can realize a defective sector 
discriminating method of extremely high reliability. 
A process carried out in the operating portion 17 is illustrated in the 
form of a flowchart in FIG. 6. In a step 105, it is determined whether or 
not an error is present in reading of the record position information 
(subcode) of an intended sector. If the record position information 
(subcode) is correctly read out, it is determined, in a step 106, that the 
sector is a usable area (information storing area). If it is determined in 
the step 105 that an error is present in reading of the record position 
information (subcode) of an intended sector, it is determined, in a step 
107, whether or not an error successively occurs n times or more in the 
medium position information (ATIP) to be accessed for read. If the number 
of successive errors is (n-1) or smaller, it is determined, in a step 108, 
that data are not yet recorded in the sector to be accessed for read, but 
the sector is a usable area (memory area having never had information 
written thereinto). If it is determined, in the step 107, that an error 
successively occurs n times or more in the medium position information 
(ATIP) to be accessed for read, it is determined, in a step 109, that the 
sector is defective and unusable. The above-mentioned processing flow in 
the operating portion 17 may be realized by a software technique or a 
hardware technique. 
In the preprocess in the present embodiment, the judgements of the steps 
107, 108 and 109 indicate the states of the sector being accessed. These 
judgements are each sent in the form of an area message to the 
input/output process 102. In response to the message, in the input/output 
process 102, information is read from the sector or information is written 
into the sector or a substitutive sector if the sector is defective. 
In the information read/write device, as of the present embodiment, which 
employs the data structure capable of dealing with some measure of burst 
error, such as the code of high error correction ability, such as CIRC, 
and the scramble, judgement on the defective sectors of the recording 
medium can easily be made by the preprocess as described above. In the 
preprocess, there is no need of repeating the read/write operation, 
whereas in the conventional "certify" process, the read/write operation 
must be repeated. In this respect, time saving is realized for users. 
Further, the preprocess in the present embodiment removes the defective 
sectors, to thereby secure a reliability of the read/write of data while 
minimizing the number of the sectors rendered unusable. Reduction of the 
memory capacity by the preprocess is less than that by the "certify" 
process. Thus, the present invention succeeds in providing an information 
read/write device of high reliability. 
In the present embodiment, even if the sector to be accessed is a sector 
having no information recorded therein, data can be written into and read 
out of that sector. The reason for this is that a read or reproduction 
clock signal is generated from the ATIP. 
Input/Output Process 
Data from the host computer 20 is written into the recording medium 11 
having undergone the preprocess as described above by the input/output 
section 12 of the information read/write device 10 in the present 
embodiment. Further, the written data are read out by the input/output 
section. In the host computer 20, the application 24 transfers data to and 
receives data from the information read/write device 10, through the OS 21 
and the input/output control portion 27 including the device driver 23. In 
the host computer 20, the application 24b directly transfers data to and 
receives data from the information read/write device 10 through the 
interfaces, not through the OS 21, viz., the input/output control portion 
27. 
Input/Output Process in the Information Read/Write Device 
In the input/output section 12 of the information read/write device in the 
present embodiment, data from the host computer to be written or recorded 
into the recording medium 11 is received by the communication portion 13, 
and temporarily stored in the device information storing portion 14 while 
leaving the data format unchanged. The data stored in the device 
information storing portion 14 is transferred as before-code-modulation 
data to the code modulating portion 15. In turn, the code modulating 
portion 15 codes and modulates the data into coded data using the CICR. 
The coded data are converted into scrambled read/write data through the 
read/write portion 16, and then is written into the recording medium 11. 
In a data reproduction or read mode, the reverse procedure is taken. The 
read/write data read out of the recording medium 11 is scrambled into the 
coded data in the read/write portion 16. The coded data are modulated and 
decoded into before-code-modulation data which is accepted by the 
computer, in the code modulating portion 15. The result is temporarily 
stored in the device information storing portion 14. The data stored in 
the device information storing portion 14 is then transferred through the 
communication portion 13 to the host computer, such as a computer. 
Through such an input/output path, the CIRC is attached as an error 
correction code to the data, and the scramble is applied to the data. A 
high reliability of the bit error rate of 10.sup.-12 can be gained as in 
other computer devices. In writing the data from the read/write portion 16 
into and reading the data out of the recording medium 11 into the 
read/write portion 16, it is desirable to handle the data in blocks of 
cluster. For example, when data are actually written enbloc into the 
recording medium 11, the data to be written enbloc must continuously be 
written into the recording medium in synchronism with the recording 
medium. Accordingly, the following inequality (2) must hold. 
EQU (transfer rate from host computer to communicatin portion)&gt;(recording rate 
to recording medium) (2) 
The transfer rate (time required for transferring data of a preset length) 
of data from the host computer depends largely on assignment of jobs, for 
example, in the host computer. The transfer rate as defined by the 
inequality (2) does not always satisfy every situation when data are 
recorded in the information read/write device. For this reason, in the 
information read/write device 10, the device information storing portion 
14 capable of temporarily storing data to be recorded enbloc, viz., at 
least the data of one cluster, is used in the input/output section 12. 
In the information read/write device 10 in the present embodiment, the 
device information storing portion 14 of a large memory capacity is used 
in the input/output section 12. The information read/write device 10 
receives from the host computer the data of one cluster as a data write 
unit for the transfer of data when it is written into the recording medium 
11 by the device information storing portion 14. After the receiving 
operation of the data is completed, the information read/write device 10 
starts the writing operation of the data into the recording medium 11. 
With provision of the device information storing portion 14, the data 
stored in the recording medium 11 can be rewritten independently of the 
transfer rate of the host computer. Accordingly, a stable information 
read/write device is realized. 
The device information storing portion 14 may have a memory capacity of two 
clusters or larger. Where the device information storing portion 14 of two 
clusters or larger is used, when data of larger than one cluster is 
recorded, an apparent transfer rate when viewed from the host computer is 
further improved. When the device information storing portion 14 of four 
clusters in memory capacity, for example, is used, the device information 
storing portion 14 receives the data up to four clusters from the host 
computer and stores the data therein independently of a write execution 
time taken when the read/write portion 16 actually writes data into the 
recording medium 11. When the device information storing portion 14 
receives data from the host computer, a message describing that the 
writing of data into the recording medium is completed may be sent to the 
host computer. With this, data transfer between the host computer and the 
communication portion is completed, the OS 21 or the device driver 23, or 
the application 26b is released from the data transfer processing. Then, 
the computer may immediately start to carry out the next job. With 
provision of the device information storing portion of a memory capacity 
larger than the data write unit for the data transfer in writing data into 
the recording medium 11, the information read/write device is capable of 
transferring data to and from the computer at high speed. 
A reprogrammable memory, such as a RAM, is most suitable for the device 
information storing portion 14. If required, any other reprogrammable data 
storing media may be used for the same. 
Sector Rewriting Method 
A rewriting process of sectors will be described with reference to the data 
structure shown in FIGS. 2(a) to 2(f) and the relationship between the 
sectors and the logic cluster in the device information storing portion 14 
shown in FIG. 7. The sector rewriting processing is carried out where the 
cluster is transferred in blocks of the data write unit. The processing 
flow is shown in FIG. 8. It is assumed that the first sector of all the 
information in the k-th physical cluster 61 on the recording medium 11, 
viz., the logical cluster 70, is a (k, 1) sector 71. To write information 
into the (k, 1) sector 71, in a step 110, data are read out in blocks of 
the physical cluster 61 from the recording medium, and all the information 
of the logic cluster substantially constituting the data in the physical 
cluster 61 are loaded into the device information storing portion 14. In 
the next step 112, the communication portion 13 receives the data of a (k, 
1) sector to be recorded from the host computer in blocks of a data unit 
for the data transfer when the computer outputs data, e.g., a data unit of 
a sector. In a step 115, the data of the (k, 1) sector, which is received 
by the communication portion 13, is developed into one sector in the 
device information storing portion 14. In a step 116, the information of 
the whole logic cluster including one rewritten sector, which contain 
additional information attached to the head and the tail of the 
information, is written into the recording medium 11. In this case, the 
information is written every physical cluster 61. To reproduce or read out 
the (k, 1) sector 71, in the steps 110 and 112, all the information of one 
cluster are read out of the recording medium. In a step 113, the execution 
of reading out (k, 1) sector 71 is recognized. In a step 117, the 
information of the (k, 1) sector 71 is read out of the device information 
storing portion 14, and sent through the communication portion 13 to the 
host computer 20 in blocks of the data unit for the data transfer in the 
computer, e.g., every sector. 
In the input/output process as of the present embodiment, no problem arises 
even if the read/write unit for the data transfer to and from the 
recording medium is different from that for the data transfer from the 
host computer. Accordingly, in the device based on the input/output 
process, the information read/write device is operable while being 
compatible with any of the host computers of different read/write units. 
As described above, the device information storing portion 14 serves as a 
useful storage portion when data are inputted to and outputted from the 
recording medium 11. With provision of the device information storing 
portion 14 which allows data to be inputted thereto and outputted 
therefrom in blocks of the read/write unit for the data transfer to and 
from the recording medium, data can quickly be inputted to and outputted 
from such a recording medium based on the scrambled recording device, 
which is insensitive to the burst error. Further, normal read/write of 
data is ensured also in such a case where the read/write unit for the data 
transfer to and from the recording medium is different from that for the 
data from the host computer. Further, the device information storing 
portion 14 has a multiple of functions, as mentioned above. This 
contributes to cost reduction of the information read/write device. 
How an area message generated in the preprocess is used in the input/output 
process is illustrated in the form of a flowchart in FIG. 9. The process 
of the step 110 to read data every cluster as shown in FIG. 8 will be 
described for more detail. To start, in a step 120, data of one sector is 
detected and read out. More exactly, data are detected and read out every 
2 kilo bytes. In this case, the preprocess, which is described in 
connection with the flowchart of FIG. 6, determines whether the sector is 
usable or unusable, and the result of the determination is sent as an area 
message. In a step 121, if the area message states that the sector is an 
information recorded area (based on the judgement in the step 106), 
control returns to the step 120 and repeats the process till data of one 
cluster is read out in a step 122. If the area message states that the 
sector is a virginal area having no information recorded therein (based on 
the judgement in the step 108), the sector is a usable area. Control flows 
to a downstream process for rewriting or writing anew data into the 
section. If the area message states that the sector is an unusable area 
(based on the judgement in the step 109), a substitutive cluster is set in 
a step 123, and the process to rewrite data or write data anew is carried 
out. When data are rewritten or written anew, the preprocess employed in 
the information read/write device in the present embodiment makes an 
access to a sector to which the data are to be rewritten or written, and 
quickly determines whether or not the sector is usable. Accordingly, a 
reliability of the read/write operation is remarkably improved without 
unnecessary consumption of time. A user can carry out the read/write 
process for a virginal recording medium having no information recorded 
therein without carrying out the "certify" processing. As a result, an 
extremely efficient work environment is provided for users. 
Input/Output Process in the Computer 
As shown in FIG. 1, the host computer 20 includes the input/output control 
portion 27. The input/output control portion 27 mainly includes the device 
driver 23, and has a write cache function in addition to the file 
buffering function. The write cache function is provided for realizing a 
high speed file access. In writing data, the data are temporarily stored 
in a memory, for example. At the end of storing the data, a write end 
signal is sent to the OS 21. Thereafter, at a proper time, the data are 
actually sent to the information read/write device 10 and recorded into 
the recording medium 11. In the input/output control portion 27 of the 
present embodiment, a part of the memory 22 in the computer is used for 
forming the device/driver information storing part 26. This device/driver 
information storing part 26 is used for the write cache. 
The device/driver information storing part 26, like the device information 
storing portion 14 in the information read/write device 10, has a memory 
capacity of one cluster or two or more clusters in association with the 
read/write unit for the data transfer to and from the recording medium 11. 
If data, which is delivered in blocks of the read/write unit for the data 
transfer to and from the recording medium 11, is temporarily stored in the 
device/driver information storing part 26 in the computer by way of the 
input/output section 12 and the device driver 23, the read/write portion 
16 may handle the input/output of data by a process similar to that for 
the device information storing portion 14. Further, the device information 
storing portion 14 in the information read/write device may be used as a 
write cache since the device driver 23 is connected to the device 
information storing portion 14, through the bus 30 and the communication 
portion 13. 
In a case where the device driver 23 uses the device/driver information 
storing part 26 in the computer as a write cache, and data are transferred 
in blocks of the read/write unit between the device/driver information 
storing part 26 and the input/output section 12 in the information 
read/write device, the bus 30 is used for transmitting and receiving data 
in blocks of the read/write unit. In a case where the device driver 23 
uses the device information storing portion 14 in the information 
read/write device as a write cache, or where the application 24b, which 
directly communicates with the information read/write device, not through 
the OS 21, is operating, data are transmitted or received in blocks of the 
read/write unit for data transfer by the OS 21 or the application 24b, 
e.g., a data unit of a sector. 
Details of Read/Write Operation 
The operation of rewriting the data recorded in the recording medium will 
be described in more detail with reference to FIGS. 10 to 11. The 
device/driver information storing part 26 in the computer and the device 
information storing portion 14 in the information read/write device have 
substantially the same functions in rewriting the recorded contents of the 
recording medium. In the description to follow, the device information 
storing portion 14 may be either of the device information storing portion 
14 per se and the device/driver information storing part 26. Rewriting 
process description will be given on the basis of the data read/write unit 
by the OS. The same process is correspondingly applied to a software, such 
as the application 24b, which directly communicates with the information 
read/write device without using the OS. 
In a case shown in FIG. 10, all the information of OS read/write 
information 91, which consists of a proper number of OS read/write units 
90, are contained in medium read/write information 97 of a medium 
read/write unit 70. Between the read/write portion 16 and the recording 
medium 11, data are transferred in blocks of the cluster unit 61. The 
medium read/write unit for the transfer of the data handled in the device 
information storing portion 14 and the like may be that of the data not 
yet scrambled. Accordingly, data can be transferred in blocks of a data 
unit having the size capable of containing the logical cluster 70 except 
the before-data additional information 62 and the after-data additional 
information 63 shown in FIG. 2. 
In a data reproduction or read mode, the medium read/write information 97 
containing the OS read/write information 91, which is to be accessed for 
read by the OS 21, is read out of the recording medium 11 through the code 
modulating portion 15, in blocks of the medium read/write unit 70. The 
medium read/write information 97 reproduced or read out from the recording 
medium 11 is stored into the device information storing portion 14. Then, 
the OS read/write information 91, which is to be accessed for read by the 
OS 21, is picked out of the information stored in the operating portion 
17, and sent to the OS 21. 
In a data record or write mode, the medium read/write information 97 
including the OS read/write information 91 is read out of the recording 
medium in blocks of the medium read/write unit, through the code 
modulating portion 15, and stored in the device information storing 
portion 14. Then, the OS read/write information 91 is received from the OS 
21, and written over the medium read/write information 97 in the device 
information storing portion 14. In other words, the medium read/write 
information 97 is updated. Finally, the updated medium read/write 
information 97 is read out of the device information storing portion 14, 
and recorded or written into the recording medium, through the code 
modulating portion 15. 
In a case shown in FIG. 11, all the information of OS read/write 
information 91, which consists of a proper number OS read/write units 90, 
are contained in a plural number of medium read/write units 70. A first 
loading method for loading the plural number of the medium read/write 
units 70 covering all the OS read/write information 91 into the device 
information storing portion 14 or a second loading method for loading the 
medium read/write units 70 unit by unit into the device information 
storing portion 14 is selectively used depending on the memory capacity of 
the device information storing portion 14. The first loading method or the 
second loading method may be selected in use on the basis of the memory 
capacity of the device information storing portion 14 and other device 
environments. Further, a third loading method, which is a compromise 
between the first and second loading methods, may be used in which two or 
more medium read/write units 70 are loaded into the device information 
storing portion 14. 
In the first loading method, in a data read mode, a first medium read/write 
unit 70a of the medium read/write information 97 containing first OS 
read/write units 90a of the OS read/write information 91 being accessed 
for read by the OS 21, and a second medium read/write unit 70b of the 
medium read/write information 97 containing second OS read/write units 90b 
of the OS read/write information 91 being accessed for read by the OS 21 
are read out of the recording medium, through the code modulating portion 
15, and then loaded into the device information storing portion 14. Then, 
the first OS read/write units 90a and the second OS read/write units 90b 
of the OS read/write information 91 being accessed for read by the OS 21 
are picked up from the information stored in the device information 
storing portion 14, and sent to the OS 21. 
In a data write mode, the first medium read/write unit 70a containing the 
first OS read/write units 90a of the OS read/write information 91 being 
not yet rewritten, and the second medium read/write unit 70b containing 
the second OS read/write units 90b of the OS read/write information 91 
being not yet rewritten are read out of the recording medium, through the 
code modulating portion 15, and loaded into the device information storing 
portion 14. Then, the OS read/write information 91 to be rewritten are all 
received from the OS 21, and written, for updating, over the medium 
read/write information 97 in the device information storing portion 14. At 
this time, the first OS read/write units 90a of the OS read/write 
information 91 is written, for updating, into the locations of the first 
medium read/write unit 70a in the medium read/write information 97 in the 
information storing portion. The second OS read/write units 90b of the OS 
read/write information 91 is written, for updating, into the locations of 
the second medium read/write unit 70b of the medium read/write information 
97 in the information storing portion. Finally, the updated medium 
read/write information 97 is read out of the device information storing 
portion 14, and written into the recording medium, through the code 
modulating portion 15. 
In the second loading method, in a data read mode, the first medium 
read/write unit 70a of the medium read/write information 97 containing the 
first OS read/write units 90a of the OS read/write information 91 being 
accessed for read by the OS 21 is read out of the recording medium, 
through the code modulating portion 15, and loaded into the device 
information storing portion 14. The first OS read/write units 90a of the 
OS read/write information 91 being accessed for read by the OS 21 are 
picked up from the information stored in the device information storing 
portion 14, and sent back to the OS 21. Then, the second medium read/write 
unit 70b of the medium read/write information 97 containing the second OS 
read/write units 90b of the OS read/write information 91 being accessed 
for read by the OS 21 is read out of the recording medium, through the 
code modulating portion 15, and loaded into the device information storing 
portion 14. The second OS read/write units 90b of the OS read/write 
information 91 being accessed for read by the OS 21 are picked up from the 
information stored in the device information storing portion 14 and sent 
back to the OS 21. 
In a data record or write mode, the first medium read/write unit 70a of the 
medium read/write information 97 containing the first OS read/write units 
90a of the OS read/write information 91 being not yet rewritten is read 
out of the recording medium, through the code modulating portion 15, and 
loaded into the device information storing portion 14. The first OS 
read/write units 90a of the OS read/write information 91 to be rewritten 
is received from the OS 21, and written, for updating, over the first 
medium read/write unit 70a of the medium read/write information 97 in the 
device information storing portion 14. Thereafter, the updated first 
medium read/write unit 70a of the medium read/write information 97 is read 
out of the device information storing portion 14, and written into the 
recording medium, through the code modulating portion 15. Then, the second 
mediumread/write unit 70b of the medium read/write information 97 
containing the second OS read/write units 90b of the OS read/write 
information 91 being not yet rewritten is read out of the recording 
medium, through the code modulating portion 15, and loaded into the device 
information storing portion 14. The second OS read/write units 90b of the 
OS read/write information 91 to be rewritten is received, and written, for 
updating, over the second medium read/write unit 70b of the medium 
read/write information 97 in the device information storing portion 14. 
The updated second medium read/write unit 70b of the medium read/write 
information 97 is taken out of the device information storing portion 14, 
and loaded into the recording medium through the code modulating portion 
15. 
In the above-mentioned loading methods, no problem arises even if the 
read/write unit for the data transfer to and from the recording medium is 
different from the OS read/write unit for the data transfer to and from 
the OS. Accordingly, the system using any of the loading methods accepts 
any type of OSs whose read/write units are different, and is normally 
operable even when the specification of the recording medium is altered 
and the medium read/write unit thereof is changed. The second loading 
method or the third loading method as a compromise between the first and 
second loading methods, effectively operates when the memory capacity of 
the information storing portion is limited. When using the loading method, 
similar useful effects can be obtained even in such a system with the 
information storing portion of a small memory capacity or a system which 
cannot use the information storing portion because its manufacturing cost 
is limited. A user who uses the information read/write device based on any 
of these loading methods can use the device while being insensible of the 
read/write unit of an OS used. In these respects, the device simple in 
construction and low in cost can be constructed. 
A case where an arbitrary number of OS read/write information are 
successively recorded into the medium read/write information 97 by 
operating the information storing portion in a write cache mode is shown 
in FIG. 12. In this case, record commands of four OS read/write 
information 91a to 91d are successively accepted. 
When a record command of the first OS read/write information 91a is 
received from the OS 21, the medium read/write information 97 containing 
the first OS read/write information 91a being not yet rewritten is read 
out of the recording medium through the code modulating portion 15, and 
loaded into the device information storing portion 14. Then, the first OS 
read/write information 91a being not yet rewritten are all received from 
the OS 21, and written over the medium read/write information 97 in the 
device information storing portion 14, so that the written information 97 
is updated into medium read/write information 97'. In this state, the 
device waits for the next command. The recording method under discussion, 
unlike the recording method already state, does not take such a processing 
that the updated medium read/write information 97' is immediately read out 
of the device information storing portion 14 and recorded into the 
recording medium. In the present recording method, in response to the next 
record command, check is made as to whether or not the information is 
recorded in the recording medium. 
Next, a record command of the second OS read/write information 91b arrives 
from the OS 21. At this time, the medium read/write information 97' 
containing part of all the second OS read/write information 91b being not 
yet rewritten has been stored in the device information storing portion 
14. Accordingly, there is no need of reading it out of the recording 
medium through the code modulating portion 15. Since the medium read/write 
information 97' resulting from updating the first OS read/write 
information 91a is not yet written, the first OS read/write information 
91a is lost if the read-out from the recording medium is carried out. For 
this reason, in the process of this instance, a process in which the 
read-out from the recording medium is successively repeated is not carried 
out except a special case. Subsequently, the second OS read/write 
information 91b to be rewritten are all received, and written over the 
medium read/write information 97' in the device information storing 
portion 14, so that the information 97' is updated into medium read/write 
information 97". In this state, the device waits for the next record 
command. Thus, as in the previous case where the first OS read/write 
information 91a is received, a process that the medium read/write 
information 97" is recorded into the recording medium through the code 
modulating portion 15, is not carried out. 
A process similar to the process upon receipt of the record command of the 
second OS read/write information 91b is carried out in response to a 
record command of the third OS read/write information 91c and a record 
command of the fourth OS read/write information 91d. 
When those processings based on the record commands have been completed, 
the medium read/write information in the device information storing 
portion 14 is successively updated by the first OS read/write information 
91a, second OS read/write information 91b, third OS read/write information 
91c, and fourth OS read/write information 91d, so that medium read/write 
information 97"" is constructed. For the medium read/write information 
97"", a record command for medium read/write information, which is 
different from the medium read/write information stored in the device 
information storing portion 14, close of a file, end of an application, 
preset elapsing times, and the like are taken out in the form of timings. 
The timings will be described in detail in the present specification. The 
medium read/write information 97"" is recorded into the recording medium 
through the code modulating portion 15. As a result, the OS read/write 
information containing all the first to fourth OS read/write information 
91a to 91d are updated in the recording medium. This recording method will 
be referred to as an ex post facto recording method. 
FIGS. 13(a) and 13(b) show the ex post facto recording method in the form 
of a flow of data between the OS 21 and the device information storing 
portion 14 with respect to time and a flow data between the device 
information storing portion 14 and the code modulating portion 15 with 
respect to time. FIG. 13(a) shows a flow of data when the ex post facto 
recording method is not used. FIG. 13(b) shows a flow of data when it is 
used. 
In FIG. 13(a), at time t1, the information read/write device receives a 
record command for the first OS read/write information 91a from the OS 21, 
and reads the corresponding medium read/write information 97 from the 
recording medium through the code modulating portion 15, and loads it into 
the device information storing portion 14. At the end of the read-out 
operation, at time t2 the information read/write device receives the first 
OS read/write information 91a and writes over the medium read/write 
information in the device information storing portion 14, so that the 
medium read/write information is updated into the medium read/write 
information 97'. When the updating operation ends at time t3, the medium 
read/write information 97' is read out of the device information storing 
portion 14, and recorded into the recording medium through the code 
modulating portion 15. When the recording operation ends at time t5, the 
information read/write device sends a record end message to the OS 21. At 
time t7, the device receives a record command of the second OS read/write 
information 91b from the OS 21, reads the corresponding medium read/write 
information 97' from the recording medium through the code modulating 
portion 15, and loads it into the device information storing portion 14. 
At the completion of the read-out operation, at time t10 the second OS 
read/write information 91b is received and written over the medium 
read/write information in the device information storing portion 14, so 
that it is updated into medium read/write information 97" At time t11, the 
updating operation ends. Then, the medium read/write information 97" is 
read out of the device information storing portion 14 and recorded into 
the recording medium through the code modulating portion 15. At time t14, 
the recording operation ends. Then, the device sends a record end message 
to the OS 21. A similar processing is successively applied to the third OS 
read/write information 91c and the fourth OS read/write information 91d. 
At time t23, the contents of the four OS read/write information are 
updated into medium read/write information 97"" which in turn is recorded 
into the recording medium. 
When the ex post facto recording method is used, the process till time t3 
is the same as that of the previous case as shown in FIG. 13(b). At time 
t3, the medium read/write information is updated in the device information 
storing portion 14. Then, the information read/write device immediately 
sends a record end message to the OS 21. In response to this, the OS 21 
sends a record command for the second OS read/write information 91b at 
time t4. In response to this command, the information read/write device 
receives second OS read/write information 91b and updates the medium 
read/write information 97 since the medium read/write information 97 
containing a data area corresponding to the second OS read/write 
information 91b is present in the device information storing portion 14. 
At time t6, the updating operation ends. Then, the device sends a record 
end message to the OS 21. Upon receipt of the message, the OS 21 issues a 
record command for the third OS read/write information 91c at time t8. A 
similar process is carried out for the third OS read/write information 91c 
and the fourth OS read/write information 91d. At time t13, the medium 
read/write information 97 in the device information storing portion 14 is 
updated by the first to fourth OS read/write information 91a to 91d into 
medium read/write information 97"". Thus, when the ex post facto recording 
method is used, the updating operations of the four OS read/write 
information is halved. The time saving effect by the ex post facto 
recording method is more effective as the number of OS read/write 
information increases. Further, there is a high probability that the data 
to be updated are closely located. Then, the opportunity to reduce the 
process time by the ex post facto recording method is very frequent. 
After the OS 21 receives a record end message at time t13, the recording 
operation for the recording medium starts at predetermined timing. Through 
the recording operation, the medium read/write information resulting from 
the updating by the first to fourth OS read/write information is recorded 
into the recording medium through the code modulating portion 15. 
Thus, when the ex post facto recording method is used, the process in the 
route including the device information storing portion 14, the code 
modulating portion 15 and the recording medium 11, viz., the read/write 
process of the medium read/write information 97', 97", 97'" and 97"" as 
shown in FIG. 13(a) can be omitted. Therefore, the time taken for the 
updating is remarkably reduced. Thus, the record executing time is 
considerably reduced. When a record command from the OS is issued to the 
same medium read/write information, the record execution time is 
remarkably reduced. When the medium read/write unit is large, the time 
taken for the read/write process of FIG. 13(a) increases in proportion to 
the size of the medium read/write information. When the ex post facto 
recording method is applied to a device whose medium read/write unit is 
large, like the information read/write device 10, the process time 
reduction effect by the ex post facto recording method is considerably 
large. The reduction of the number of the read/write commands leads to the 
reduction of the number of the operations of writing information to the 
recording medium. As a result, a reliability of the recording medium is 
improved. 
When the ex post facto recording method is employed for the information 
read/write device, it is preferable to use an information storing portion 
large enough to store several medium read/write units. By so doing, a more 
quick response to the read/write command from the OS is realized. 
In the above-mentioned embodiment, four OS read/write information are 
written over the same medium read/write information and stored. When more 
than four OS read/write information are written over the medium read/write 
information and stored, the process time reduction effect is further 
enhanced as described above. 
The process effect that has been described with reference to FIGS. 10 to 13 
is obtained in both the information read/write device 10 and the host 
computer 20, as described above. If the device/driver information storing 
part 26 and the device driver 23 in the host computer 20 are used for the 
process of updating the information, the process speed is further 
improved. FIG. 14 shows a flow of data in a case where the device driver 
23 and the device/driver information storing part 26 in the input/output 
control portion 27, which is contained in the host computer, are used for 
the updating process, and the above-mentioned read/write information unit 
conversion method and the ex post facto recording method are employed. In 
the figure, the operation of the device driver 23 in this device is 
described in the form of a flow of data between the OS 21 and the device 
driver 23, and a flow of data between the device driver 23 and the 
information read/write device 10 (corresponding to the bus 30). In the 
case shown in FIG. 14, three record commands for the first to third OS 
read/write information 91a to 91c are successively issued. 
In FIG. 14, at time t31, the device driver 23 receives an information 
handling start command from the OS 21, and recognizes that information in 
the information read/write device 10 is to be written and read out. 
Thereafter, at time t32, the OS 21 issues a record command for the first 
OS read/write information 91a toward the device driver 23. Upon receipt of 
the record command for the first OS read/write information 91a, the device 
driver 23 operates according to the read/write information unit conversion 
method, and at time t33 issues a read command for the related medium 
read/write information 97 toward the information read/write device 10. In 
response to the read command, the information read/write device 10 reads 
out the medium read/write information 97 in blocks of the medium 
read/write unit, from the recording medium. At time t34, the device 
transfers the medium read/write information 97 to the device driver 23 by 
way of the bus 30, and sends an end procedure to the device driver 23. 
Then, the device driver 23 stores the medium read/write information 97 
containing a data area corresponding to the first OS read/write 
information 91a being not yet rewritten in the device/driver information 
storing part 26, in the state of the medium read/write unit, and at time 
t35 receives the first OS read/write information 91a to be rewritten, from 
the OS 21. Then the device driver updates the medium read/write 
information 97 into medium read/write information 97' in the device/driver 
information storing part 26. At time t36, the overwriting and storing 
process ends, and the device driver 23 issues a first write end procedure 
to the OS 21. 
In response to this, at time t37, the OS 21 issues a record command for the 
second OS read/write information 91b to the device driver 23. In response 
to this command, the device driver 23 immediately receives the second OS 
read/write information 91b to be rewritten from the OS 21, and carries out 
the overwriting and storing process in the device/driver information 
storing part 26 since the medium read/write information 97 to be rewritten 
has been present in the device/driver information storing part 26. At time 
t38, the overwriting and storing process ends, the device driver 23 issues 
a second record end procedure to the OS 21. 
At time t39, a record command for the third OS read/write information 91c 
is issued from the OS 21 to the device driver 23. In response to this 
command, the device driver 23 immediately receives the third OS read/write 
information 91c to be rewritten from the OS 21 since the related medium 
read/write information 97 to be rewritten has been present in the 
device/driver information storing part 26. In the device/driver 
information storing part 26, the overwriting and storing process is 
carried out and medium read/write information 97'" is produced. At time 
t40, the overwriting and storing process ends, the device driver 23 issues 
a third record end procedure to the OS 21. 
Thereafter, the OS 21 recognizes that the operations by all the record 
commands have been completed, and at time t41, it issues an information 
handling end command to the device driver 23. This information handling 
end command, issued by the OS 21, is used for informing the device driver 
23 that no further read/write process for the information will be carried 
out. In this instance, this command is used as the predetermined timing to 
record information into the recording medium. The information handling 
start command issued at time t31 and the information handling end command 
issued at time t41 are used within the host computer 20, and not directed 
to the information read/write device 10. These information handling start 
command and the information handling end command are issued at time 
positions to start and to leave off the read/write process of information. 
Therefore, it is most suitable for the timing at which information is 
recorded. The device driver 23, at time t41, receives the information 
handling end command, and at time t42, issues a record command to the 
information read/write device 10, so as to cause the device to write 
medium read/write information into the recording medium. At the same time, 
the device driver 23 transfers the medium read/write information 97'", 
which is stored in the device/driver information storing part 26, through 
the bus 30 to the information read/write device 10. Upon receipt of the 
record command, the information read/write device 10 receives the medium 
read/write information 97'", and writes it into the recording medium. At 
the completion of the recording of the information, at time t43, the 
information read/write device sends an end procedure to the device driver 
23. 
As described above, by using the device/driver information storing part 26 
in the memory of the host computer, the information handling end command 
computer may be used as host computer may be used as the predetermined 
timing. By using the timing, information may be written into the recording 
medium by the ex post facto recording method. With the recording of 
information into the recording medium by the information handling command, 
when a power source of the information read/write device is different from 
that of the host computer, and the former power source is turned off, 
displayed characters in the host computer can give a user warning. In 
other words, a good data protection is secured. Also when the recording 
medium is removed from the information read/write device, the displayed 
characters give the user warning. With this function, when the user 
mistakenly understands that information has been recorded into the 
recording medium, and removes the recording medium from the information 
read/write device or turns off the power switch, the display in the host 
computer arouses the user's attention. After seeing the display, the user 
restores the information read/write device to its original state, and can 
use the information still alive in the memory of the host computer. 
Since the number of the read/write commands issued to the information 
read/write device is reduced, a high speed file access is realized. 
While in the present embodiment, three record commands are successively 
issued from the OS to the device driver, more than three record commands 
may be successively issued, and the record command and the read command 
may be used in a mixed way. 
Input/Output Process by an Application 
A process in which the application shown in FIG. 1 inputs and outputs data 
to and from the recording medium 11 by using the information read/write 
device 10, will be described. The application includes an application 24a 
for inputting and outputting data through the OS, and the application 24b 
which directly accesses the information read/write device 10, not through 
the OS, and inputs and outputs data to and from the recording medium. 
A case where the application 24a writes data into and reads data from the 
recording medium 11 by using the information read/write device 10, will be 
described. When the application 24a desires to use specific information, 
viz., in a data read mode, the application issues a read command to the 
device driver 23, through the OS 21. In response to this command, the 
device driver 23 converts the OS read/write unit to the medium read/write 
unit by using the read/write information unit conversion method, in the 
device/driver information storing part 26. As a result, the device driver 
23 issues a read command to the information read/write device 10 so as to 
read out medium read/write information of the converted medium read/write 
unit. The information read/write device 10 receives the read command by 
the communication portion 13, and the control portion 18 controls the 
blocks to read out the medium read/write information from the recording 
medium 11, and sends the read out information to the device driver 23 in 
the host computer 20, through the communication portion 13. In turn, the 
device driver 23 sends OS read/write information to the OS 21 by using the 
read/write information unit conversion method, in the device/driver 
information storing part 26. The OS 21 transfers this information to the 
application 24a. By the process flow, one read command of the application 
24a is executed. 
When the application 24a desires to store specific information into the 
recording medium 11, viz., in a data write mode, the flow of information 
is reversed. An information record command and information are transferred 
to the device driver 23 through the OS 21. Then, the device driver 23 
records information into the recording medium 11 through the communication 
portion 13 in the information read/write device 10, by the read/write 
information unit conversion method using the device/driver information 
storing part 26, and the ex post facto recording method. 
The application 24b directly writes information into and reads information 
from the recording medium, not through the OS and the device driver. When 
the application 24b desires to use information, viz., in a data read mode, 
it issues an information read command to the communication portion 13 in 
the information read/write device 10. In response to this command, the 
control portion 18 converts the read/write unit of the application 24b to 
the medium read/write unit by the read/write information unit conversion 
method that is operated in the device information storing portion 14 of 
the information read/write device. The read/write unit may be exactly 
equal to the OS read/write unit. The program per se of the application 24b 
runs under control of the OS 21, and hence it can know the OS read/write 
unit. When the application 24b releases the information read/write device 
and another application uses the information read/write device 10, the 
application 24b is placed to a read/write impossible state. To avoid this, 
it is preferable to set the read/write unit to be exactly equal to the OS 
read/write unit. After the information read/write unit of the application 
24b is converted, the control portion 18 controls other blocks to read the 
medium read/write information at the medium read/write unit, from the 
recording medium 11, and loads it to the device information storing 
portion 14. The control portion 18 converts the read/write unit of the 
read out medium read/write information 97 to the information read/write 
unit of the application 24b, and sends the read out information at the 
converted read/write unit to the application 24b, through the 
communication portion 13, and ends the read process. 
When the application 24b desires to store specific information, viz., in a 
data write mode, the application 24b directly delivers an information 
read/write command and information to the communication portion 13 in the 
information read/write device 10. The control portion 18 in the 
information read/write device 10 converts the read/write unit of the 
application 24b to the medium read/write unit by the read/write 
information unit conversion method using the device information storing 
portion 14, and writes information into the recording medium 11 by 
controlling other blocks. 
As described above, in the information read/write device 10, the device 
information storing portion 14 capable of storing data of the medium 
read/write unit is included in the input/output section 12. With provision 
of the device information storing portion 14, the read/write unit of data 
is converted and recorded in the device information storing portion. 
Therefore, if a user uses an application which directly accesses the 
information read/write device, not through the OS and the device driver, 
and inputs and outputs data to and from the recording medium, no problem 
arises and a recording medium of large read/write unit, such as the CD 
rewritable at high processing speed, can be used. The data written or read 
out under control of the OS is not destroyed even if the power source of 
the information read/write device is turned off or the recording medium is 
removed therefrom. In other words, a good data protection is secured. When 
data are written or read out not using the OS, the data are left in the 
device information storing portion in the information read/write device. 
Therefore, the data can be protected even if the recording medium is 
mistakenly removed from the information read/write device. 
Timing of Record 
A time point of reading out OS read/write information for different medium 
read/write information or of issuing a record command, a time point of 
issuing an information handling end command used within the host computer, 
and the like may be used as the timing to write information updated or 
prepared at the medium read/write unit by the read/write information unit 
conversion method and the ex post facto recording method into the 
recording medium. In a case where the device/driver information storing 
part 26 necessary for using the read/write information unit conversion 
method and the ex post facto recording method secures its memory capacity 
of the minimum medium read/write unit in the memory 22 when the host 
computer 20 is started up, for example, four medium read/write units are 
secured for the device/driver information storing part 26, how information 
is inputted to and outputted from the information read/write device 10 
will be described. 
An information handling end command as the predetermined timing in the ex 
post facto recording method may be used in both the read/write operation 
using the OS 21 and the device driver 23 and the read/write operation 
without using them. However, before the information read/write end command 
is issued, there is a case that the entire memory area of the 
device/driver information storing part 26 is filled with the medium 
read/write information, which is not recorded in the recording medium, 
viz., a buffer full is set up. If the information read/write end command 
alone is used as the predetermined timing in this full buffer state, no 
response is possible to an information read/write command for the medium 
read/write information, not present in the device/driver information 
storing part 26. Accordingly, after the buffer full state, when a 
read/write command for the medium read/write information, not present in 
the device/driver information storing part 26, is received from the OS 21, 
an instant that the read/write command is received (a buffer full timing) 
is also used as the predetermined timing, and the medium read/write 
information in the device/driver information storing part 26 is recorded. 
As a result, the memory area of the device/driver information storing part 
26, which is occupied by the medium read/write information recorded in the 
recording medium or transferred to the information read/write device 10, 
may be used for storing the mediumread/write information to be read out by 
a read/write command from the OS 21. 
Art eject command issued from the information read/write device 10 may be 
used as timing, and the information that is stored in the device 
information storing portion 14 or the device/driver information storing 
part 26, is recorded into the recording medium. When the application ends 
its operation, it closes the file under control of the OS. This is true 
for most of the applications. Accordingly, if this command is used as the 
timing, the data that have been formed or rewritten are read out of the 
device information storing portion 14 or the device/driver information 
storing part 26, and recorded into the recording medium. Some of the 
applications do not issue file close commands. In such applications, the 
data that have been formed or updated are left while not recorded. This 
problem may be solved in a manner that the data of the device information 
storing portion 14 or the device/driver information storing part 26 are 
recorded into the recording medium in response to an eject command for 
ejecting the recording medium. By so doing, such an unwanted situation 
that the data formed or updated during the operation of the application 
disappears while not recorded can be avoided. 
The timer 25 is included in the input/output control portion 27. By using 
the timer, preset elapsing times may be written as timings into the 
recording medium. A situation that a read/write command has not been 
issued for a long time from the OS 21, and an information handling command 
has also not been issued for a long time, rarely takes place. However, 
this is very dangerous situation in keeping the recorded data. To avoid 
this, intervals of times the read/write commands are received from the OS 
21 are measured by the timer 25. When a read/write command is not issued 
for a preset time from the OS 21, the medium read/write information, which 
is stored in the device/driver information storing part 26 and not yet 
recorded into the recording medium, is transferred to the information 
read/write device 10 and recorded into the recording medium 11. 
If the buffer full timing and a time elapsing from the final read/write 
operation are used for the given timings, in addition to the information 
handling end command, a stability and a reliability of the information 
read/write device are remarkably improved. 
It is evident that the data structure and the number of bytes of the 
cluster, for example, are not limited to those mentioned above. In the 
above-mentioned embodiment, the information storing portions are included 
in the information read/write device and the host computer, respectively. 
However, even if an information storing portion is included in either of 
them, the information of different read/write units may smoothly be 
converted as described above. 
As described above, where the preprocess of the present invention is used, 
it is possible to determine whether or not a sector is usable by using the 
medium position information previously recorded in the recording medium 
and the record position information protected by a strong error correction 
code, and by making use of a difference of the easiness of read error 
occurrence between those position information. Further, the occurrence of 
unusable sectors may be controlled to be a proper quantity for a recording 
medium used, by properly selecting a defect factor of the recording medium 
and an error rate of the medium position information. Where the preprocess 
is used, a process can be carried out while judging whether or not a 
sector is usable, without certifying the recording medium. Accordingly, a 
user can effectively use the recording medium of large memory capacity in 
good work environment, not bothering with the "certify" process consuming 
tremendous time. 
The information storing portion for temporarily storing information of the 
read/write unit equal to or larger than that of the recording medium is 
used in the present invention. With provision of the information storing 
portion, the read/write process can stably be carried out in the 
information read/write device, independently of external factors, such as 
the transfer rate of the host computer. 
It should be understood that the above described embodiment may variously 
be changed, modified and altered within the present invention. For 
example, the present invention is applicable to a mini disc, usually 
abbreviated as MD, which uses the CIRC as basic structure. 
Further, by using the information storing portion, the read/write unit of 
the data recorded in the recording medium is easily converted into the 
read/write unit of the data received from the OS, for example, and vice 
versa. Accordingly, the device can deal with all the read and write 
commands from the OS. When a plural number of recorded information are 
temporarily stored in the information storing portion, and then are 
recorded at given timing, a further improvement of the processing speed is 
secured. In a device where the read/write operations are repeated several 
times, the execution time for these write operations is omitted, and hence 
the information recording speed is further improved. 
When the information storing portion is provided outside the information 
read/write device, for example, in the host computer, the information 
updating speed is improved. Further, when the power source of the 
information read/write device is turned off or the recording medium is 
removed therefrom, there is eliminated the information being left 
unrecorded. In this respect, an excellent data protection is secured in 
the information read/write device. When an instant that an information 
handling end command, synchronized with the OS, is used for the given 
timing to record information into the recording medium, a further 
reduction of the record execution time and a safety of process are 
secured. 
Also, it is evident that the processing method and the input/output device, 
which use the information storing portion, are applicable to normal 
read-only CDs, in addition to rewritable CDs. Accordingly, rewritable CDs 
and read only CDs can be driven by a single information read/write device. 
In other words, a user can use the information read/write device without 
bothering the type of CDs used such as a rewritable CD or read only CD.