SCAN AND READ CONTROL APPARATUS FOR A DISK STORAGE DRIVE IN A COMPUTER SYSTEM

• US 3,848,235 A
• Filed: 10/24/1973
• Issued: 11/12/1974
• Est. Priority Date: 10/24/1973
• Status: Expired due to Term

• Current Assignee: David Otto Lewis, Thomas Howard Miller
• Original Assignee: David Otto Lewis, Thomas Howard Miller
• Inventors: Lewis, David Otto, Miller, Thomas Howard
• Primary Examiner(s): Shaw, Gareth D.
• Assistant Examiner(s): Chapnick, Melvin B.
• Application Number:
  US05/409,215
• Time in Patent Office: 384 Days
• Field of Search: 340/172.5,173RC,174.1H
• US Class Current: 711/111
• CPC Class Codes: G11B 5/596 for track following on disks G11B5/5526, G11B5/5552, G11B5/5565, G11B5/5582 take precedence
• CPC Class Codes: G11C 7/10 Input/output [I/O] data interface arrangements, e.g. I/O data control circuits, I/O data buffers
• CPC Class Codes: Y10S 707/99931 Database or file accessing

Abstract

Control apparatus for controlling a disk storage drive attachment in a computer system whereby records stored on the disk storage media are scanned and read within the same data field. The search key or search argument contained in main storage of the computer system is retrieved and compared with the key in the disk data field being scanned. The storage locations in the scan field not containing the search key are set to hexidecimal FF. The central processing unit (CPU) of the computer system is in a write to disk storage drive mode whereby the search argument is transferred from storage to the disk storage drive attachment as data is read from the disk storage drive. Decode apparatus senses the first hexidecimal FF from storage and switches the operation from a scan mode into a read mode and if a scan low or equal condition resulted from the comparison, the disk data field is read into the storage scan field with one byte of FF between the search key in storage and the newly stored disk data. The one byte of FF still provides an indication of the end of the search key. The operation then switches back to the scan mode and repeats in the manner described, i.e., sequential disk data fields are read into the storage scan field, until a comparison of equal or high results. When a high condition exists, a latch is set to block the storage of disk data in main storage because the storage scan field now contains the disk data field which had been sought, i.e., the one containing the desired index key.

Claims

1. In a computer system including main storage, a central processing unit, a disk storage drive, a disk storage drive attachment for connecting said disk storage drive to said central processing unit, the improvement comprising means for reading bytes of data from a disk data field in said disk storage drive containing data to be entered into said main storage, means for reading bytes of data from a scan field in main storage having a search key with the remaining bytes therein set to a predetermined coded value distinguishable from said search key, compare means for comparing bytes of data read from said scan field with bytes of data read from said disk data field and indicating a compare condition, decoding means responsive to the first byte of said scan field having said predetermined coded value distinguishable from said search key for generating a mode switching signal, and means responsive to said mode switching signal and a compare condition for transferring bytes of data read from said disk data field to said scan field in main storage.

2. The computer system of claim 1 wherein said compare condition is a low compare condition.

3. The computer system of claim 1 where said scan field has a length one byte greater than the length of said disk data field.

4. The computer system of claim 1 where said search key is located at the head of said scan field.

5. The computer system of claim 1 wherein the bytes from said disk data field are transferred into said scan field to be separated from said search key therein by at least one byte having said predetermined coded value distinguishable from said search key.

6. The computer system of claim 1 wherein said predetermined coded value distinguishable from said search key is hexidecimal FF.

7. The computer system of claim 1 further comprising means responsive to said mode switching signal and a compare high condition for inhibiting the entry of bytes from said disk data field into said scan field.

8. In a computer system including a main storage for storing instructions and data, a central processing unit connected to said main storage for retrieving and storing instructions and data in said main storage and including means for executing said instructions and performing arithmetic and logic operations upon said data, a disk storage drive including disk media for storing data records on the surface thereof where said records include index records, each index record having a data field with at least one index key and an index key identification within said data field, a disk storage drive attachment connecting said disk storage drive to said central processing unit and operable in response to signals from said central processing unit and from said disk storage drive for controlling said disk storage drive in seek, read, write and scan modes, the improvement comprising scan field storage positions in main storage with a first group of storage positions thereof set to represent a search key and with the remaining storage positions of said scan field set to a predetermined coded value distinguishable from said search key, and means for perforMing a combined scan and read operation whereby said index key in said disk data field is scanned and compared with said search key in said scan field and upon detecting said storage positions set to said predetermined distinguishable coded value said index key identification is transferred into said remaining storage positions of said scan field.

9. The computer system of claim 8 wherein said search key is positioned at the head of said scan field.

10. The computer system of claim 8 wherein said means for performing a combined scan and read operation blocks entry of said disk data field into said scan field when said index key compares high to said search key.

11. In a computer system including a main storage for storing instructions and data, a central processing unit connected to said storage for retrieving and storing instructions and data in said main storage and including means for executing said instructions and performing arithmetic and logic operations upon said data, a disk storage drive including disk media for storing data records on the surface thereof where said records include index records, each index record having a data field with at least one index key and an index key identification within said data field, a disk storage drive attachment connecting said disk storage drive to said central processing unit and operable in response to signals from said central processing unit and from disk storage drive for controlling said disk storage drive in seek, read, write and scan modes, the improvement comprising a scan field storage positions in main storage with a first group of storage positions thereof set to represent search key at the head thereof and with the remaining storage positions of said scan field set to a predetermined coded value distinguishable from said search key, means in said disk storage drive attachment responsive to predetermined control signals from said central processing unit for initiating a scan and read operation control signal, selectively operable transfer means in said disk storage drive attachment for initiating sequential transfer of the contents of said scan field storage positions to said disk storage drive attachment and for simultaneously initiating sequential transfer of data from said disk data field, selectively operable comparing means responsive to said scan and read operation control signal for sequentially comparing the contents of sand scan field with the contents of said disk data field and providing compare low and compare high indications, decoding means connected to receive the sequential transferred contents of said scan field and responsive to detecting said coded value distinguishable from said search key for generating a switch mode signal, and means responsive to said switch mode signal for stopping said comparing means and for causing said selectively operable transfer means to discontinue transfer of the contents of said scan field and initiate sequential transfer of the remainder of data from said disk data field to said central processing unit for storage in said main storage within said remaining storage positions of said scan field.

12. The computer system of claim 11 wherein the remainder of said disk data field is stored in said scan field and separated from said search key by said coded value distinguishable from said search key.

13. The computer system of claim 11 further comprising means responsive to said switch mode signal and a compare high indication for generating a signal to inhibit the entry of the remainder of said disk data field into the scan field in main storage.