Abstract: A record disk player removably receives for rotation a record disk having an index mark as the sole circumferential position indicator. A spindle in the player has a tachometer with marks angularly displaced a distance equal to the disk storing a predetermined number of bytes on the respective record tracks. A byte counter counts byte periods and is reset by each of the tachometer marks for indicating offset of the marks from the index signal. A register stores the offset as determined by the count in the segment counter at index time. A segment counter counts tachometer pulses for indicating which of the segments are currently being scanned on the record disk. The segment count when coupled with an offset indication provides true rotational position to a byte granularity. The index pulse resets the tachometer counter to zero. The tachometer counter has a modulus equal to the number of groups of bytes (segments) in each of the record tracks.

Abstract: An updatable and expandable directory structure and resultant access procedures emulating a write-once or indelible record medium to a rewriteable record medium as to accessing characteristics. The directory is indexed; one directory header for a first set of files indexes another set of files. Sector clusters or data extents are managed such that random recording from any file proceeds independently of write-once characteristics. The directory is stored on the medium as data is recorded. Each directory entry contains an archival history of recording of a related data file in the medium. Both logical and physical addressing is employable.

Abstract: A data recorder, preferably of the magnetooptic type, employs a rotating record storage disk. The record storage disk has a track starting primary data storing sector circumferentially adjacent to the track starting sector or a small plurality of alternate data storing sectors which are not addressable directly by mechanisms outside of the recorder as are the primary recording sectors. Whenever a one of the primary sectors in a given track is found to be defective, then one of the alternate sectors in that same track receives data from a one of the primary storing records of sectors in the same track. A small number of alternate sectors are selected to extend circumferentially for creating an elapsed scan time over the element of sectors not less than the elapsed time required for the recorder to switch from scanning one track to scanning an adjacent one of the tracks.

Abstract: A data recorder employs a disk record having a spiral track with either magnetically or optically sensible indicia. A normal mode of operation is to repeatedly scan one turn or circumvolution of the spiral track for emulating a circularly closed track. The recorder responds to received commands from a utilization device to tailor the disk access and recovery operations to the received command based upon command parameters and current status of the disk record. Electrical circuit and programming arrangements for effecting the controls are disclosed.

Abstract: Data recording is self-archiving by non-delete recording combined with a directory that grows with each recording in a manner that all previous recordings related to the respective files or data sets are pointed to in the directory. Non-delete recording is applicable to those record media exhibiting indelible characteristics, such as write-once optical media and to rewritable media, such as magnetic recording media of all types. Each directory entry is identified by file or data set name and has one field for each data segment currently a part of the file or data set. Each field has a pointer to its represented data irrespective of when it was recorded. Each directory entry also points to the entry associated with the immediately preceding recording operation on any part of the file or data set such that data changes can be traced using the directory.