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Circular Scan of VTOC Usage Map

IP.com Disclosure Number: IPCOM000047222D
Original Publication Date: 1983-Oct-01
Included in the Prior Art Database: 2005-Feb-07

Publishing Venue


Related People

Chou, JK Churgovich, DM Howell, DM Troyer, SR [+details]


In a diskette drive, data is stored on the floppy disk in storage locations of a predetermined size referred to as sectors. A Volume Table Of Contents (VTOC) stored at a predefined location in a predetermined number of sectors on the diskette contains records that point to the sector storage location of files stored on the diskette. When the diskette is first loaded into a using system, its VTOC is read into the processor. The processor also generates a usage map of the VTOC to keep track of the allocation of VTOC sectors. For each new allocation, the VTOC usage map is scanned in a circular or wrap-around manner from the last allocation rather than being scanned from the beginning of the map. In the example described herein, each sector has a capacity of 256 bytes. Each VTOC sector can contain two 128-byte record labels.