DATA FILING SYSTEM

Abstract: A data filing system comprises a disk memory for stor­ ing a plurality of files. At the beginning of all the files, a file number area or a file header is provided for storing the number of files stored. The saving and the loading of the da­ ta can be carried out by skipping the file number in the file header to directly reach a selected file. Preferably, the disk is of a sequentially access type floppy disk.

Description: DATA FILING SYSTEM BACKGROUND OF THE INVENTION The present invention relates to a data filing system for a floppy disk and, more particularly, to a data filing system for a sequential access type floppy disk. Conventionally, many kinds of data recording media for a personal computer have been available from a Compact Magnetic Tape (CMT) for a tape recorder to a Mini-Floppy Disk (MFD). The MFD is not inexpensive. Usually, the operators of the personal computers use the CMT because it is reasonable, compact, and highly reliable. However, the CMT cannot provide high speed data transfer capability to thereby need a long time for loading and saving a program, disadvantageously. An improved, sequential access type floppy disk system has been designed, and has been marketed in Japan as part of their MZ 1500 personal computer by Sharp Kabushiki Kaisha. SUMMARY OF THE INVENTION The present invention is concerned with an improved data filing system for a floppy disk data storage medium. The invention is particularly applicable to a sequential access type floppy disk, and is intended in its preferred embodiment to expand its storage capacity as much as possible. Briefly described, in accordance with the present invention, a data storage system comprises disk memory means for storing data as files according to the length of the data, data header means positioned at the beginning of the files for storing the number of the files presently stored in the disk memory means, and file control means responsive to the file number of the file header means for controlling the saving and the loading of the files. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention and wherein: FIG. 1 shows a format of a data storage medium for a data filing system according to the present invention; and FIGS. 2, 3, and 4 show data storage examples in the data format of the medium of FIG.1; FIG. 5 shows a data format of a file number area for the medium of FIG. 1; FIG. 6 shows a data format of a program file for the medium of FIG. 1; FIG. 7 shows a block diagram of an interface circuit of a sequential access type floppy disk for use in the present invention; and FIGS. 8, 9(1), 9(2), 9(3), and 10 show flow charts of the various operations of the data filing system according to the present invention. DESCRIPTION OF THE INVENTION FIG. 1 shows a data format of a medium for the present invention. First, the principle of filing data in accordance with the present invention is explained. Instead of separating a medium into a plurality of blocks each having a predetermined standard size, each file is treated as having an optional length in conformance with the data size of a program file. Such a data filing system is advantageous in that a file gap between blocks not storing data can be minimized, so that the data storage capacity of the medium can be expanded as wide as possible. A gist of the present data fling system is to position a single file called herein a file number area or a file header area at the beginning of the data storage file of the medium. The file number area or the file header area is provided for storing the file number as being presently stored in the medium. Based on the file number stored in the file number area, the data filing is controlled according to the present invention. Therefore, prior to using a new data storage medium, a figure "0" must be registered into the data file number area. This is referred to a data format operation for the medium. FIG. 1 shows a format for use in such a data format operation. With reference to FIG. 1, there is provided a file number area 1 to which the figure "0" should be stored upon its data format formation and usually a file number FN is stored. The data storage medium has a plurality of storage areas 29 between a medium top 8 and a medium end 7. After preparing the data storage format, eah time a single file is stored in the medium, the contents of the file number area 1 are increased by 1. When a new file is stored, the position of storing the file in the medium is determined according to the file number stored in the file number area 1, so that a new file is stored just following the recently-stored file, subsequently. Selecting the file number enables a new file to be stored just following the file selected by the file number (In this case, all the files stored following the newlystored file are made in vain). The data filing system of the present invention will be described specifically. FIG. 2 shows a condition of having stored three program files 2, 3, and 4 in the medium while the file number area 1 stores "3" as the file number FN. To further store a fourth file "D", the contents "3" of the file number area 1 are read-out, first. Second, the three files 2, 3, and 4 referred respectively to "A", "B", and "C in FIG. 2, are skipped through. When a file end flag of the third file 4 is detected which is stored at the last portion of thereof, a file gap for separating the two files is written-in of a predetermined length. The file gap is an area in the data storage which is used mainly to indicate the end of the third file 4 and the beginning of the fourth file 6. Following this file gap 5, the fourth file 6 referred to "D" is stored. At this time, the contents of the file number area 1 remain "3". While the fourth file 6 is being written, If the data length of thid file 6 does not reach the medium end 7, it is meant that this file 6 could be stored in the medium. Next, the file number in the file number area 1 is renewed. On account of the structure of the sequential access type floppy disk, when a head is started, regardless of either the save or the load operation, the head is continued to be rotated until it is positioned at the medium end 7. Therefore, all the operations start at the position of the medium top 8. Referring to the abovedescribed specific example, after the file 6 has been stored, the head is rotated to the medium end 7 and then come back to the medium top 8. During this operation, the previous file number is renewed by "+1", so that a new file number "4" is registered. After the file number is renewed, the head is activated to the medium end 7 at which the file registration ends. By using this period, the presently-stored file 6 can be verified as shown in FIG. 4. Thus, a new file is stored just following the preceding file, subsequently. When the medium end 7 is reached during the file registration, it is detected that no space for storing the file remains in the" medium, so that the registration of the file is cancelled. In such a case, the file number is not renewed. Thus, the files can be stored or registered. The stored files can be accessed or loaded as described below. To load the files, the file name is selected so that the file can be accessed which is stored at any location on the medium. Based on the contents of the file number area 1 and the contents of every information block, it is detected whether the selected file name is stored on the medium. The information block is provided at the beginning of every file. Every file is skipped through until the file name of the information block equals the selected file name. When the number of the skipped files equals the file number as represented by the contents of the file number area 1, it is detected that the selected file to be read-out is absent in this medium. FIG. 5 shows a data format of the file number area 1. FIG. 6 shows a data format of the program file. These formats are examples when an interface of Z-80 Serial Input/Output (SIO), produced by Sharp Corporation, Japan, is used between a Central Processing Unit (CPU) and the floppy disk and a Synchronous Data Link Control Protcol mode is employed to receive/transmit the data. With reference to FIG. 5, a first area 9 is provided for storing the SIO external circuit bit synchronous data data for a predetermined time, e.g., "OOH" data. A second area 10 is provided for storing SIO synchronous characters for a predetermined time, e.g., "7EH". A third area 11 is provided for storing SIO station address for a predetermined time, e.g., "55H". A fourth area 12 is provided for storing the file number or the number of presently storing the files, e.g., "0" to "FFH". A fifth area 13 is provided for storing a CRC character data of 2 bytes. A sixth area 14 is provided for storing the end flag for a predetermined time, e.g., "7 EH". In FIG. 6, an information block 30 storing the file name comprises an area 15 of 1 byte storing the type of program file, an area 16 storing the file name, an area 17 of 2 byte storing the byte size of the file data, an area 18 storing the top address of the data, and an area 19 storing execution address for this file, all as the control data. The storage data 20 is contained in a further area 20. The control data such as the file name and the bit size are counted as a single file and the storage data are counted as another file. FIG. 7 shows a block diagram of the interface circuit. The circuit of FIG. 7 comprises a Z-80 SIO circuit 21, an FM modulation circuit 22, a basic clock generator 23, a crystal oscillator 24, a sequential access type floppy disk 25, an external synchronous circuit 26, and a personal computer 28. A control signal 27 is generated by the Z-80 SIC circuit 21 to switch on the motor and make it ready. The data are transmitted to the sequential access type floppy disk 25 with the FM modulation. The bits of the data read-out from this disk 25 are synchronous by the external synchronuous circuit 26 to be forwarded into the Z-80 SIC circuit 21. The basic clock generator 23 is provided for providing basic clocks determining data transference speed. The reset signal for the external synchronous circuit 26 is generated by a CPU, so that the bit of the file gap is made synchronous. FIGS. 8 through 10 show flow charts of the various operations of the data storage system of the present invention. FIG. 8 is a flow chart of the data format operation as described with reference to FIG. 1. FIGS. 9(1) through 9(3) are flow charts of registering or saving the files. FIG. 10 is a flow chart of accessing or loading the files. As described above, in accordance with the present invention, the storage capacity of the data storage medium can be utilized in its maximum. It become possible to register (save) a plurality of files and access (load) some optional files, advantageously. The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention. There are described above novel features which the skilled man will appreciate give rise to advantages. These are each independent aspects of the invention to be covered by the present application, irrespective of whether they are included within the scope of the following claims.

Claims: CLAIMS: 1. A data storage system comprising: disk memory means for storing data as files according to the length of data; data header means positioned at the beginning of the files for storing the number of the files presently stored in said memory means; and file control means responsive to the file number in the file header means for controlling the saving and the loading of the files. 2. The system of claim 1, further comprising skip means responsive to the file number in said file header means for skipping the previously stored files to directly reach a data blank portion. 3. The system of claim 1, further comprising a frequency modulation circuit, a basic clock generator, and an external synchronous circuit. 4. The system of claim 1, wherein the content of said file header means is renewed each time a new file is stored in said memory disk means. 5. A sequential access data filing system operable to read a data header stored on a storage medium in front of a plurality of files and to determine from said header how many files are stored, the apparatus being further operable in response to said determination automatically to condition itself for recording a further data file at a position on said storage medium following said plurality of stored files. 6. A system as claimed in claim 5, which is operable to store data files of variable length.

Inventors: OKAMOTO, SHINJI
Applicants: SHARP KABUSHIKI KAISHA
Application year: 1984
Main classification: G11B20
IPC codes: G06F3, G06F12, G11B20, G11B27