System and method for formatting high density storage media

Claim 2

In a computer system having at least one high density data storage medium, said data storage medium having a large number of data storage subdivisions and requiring lengthy format times, a system for formatting said medium on a time-distributed basis, said formatting system comprising: means for maintaining a record of status information for each of said subdivisions, said status information including an indication of whether or not said subdivision has been formatted; means for determining when said com­puter system is disk-idle; means responsive to said disk-idle determining means and to said status information record maintaining means for selecting an unformatted one of said subdivisions when said computer system is disk-idle; and means for formatting an unformatted one of said subdivisions responsive to one of (a) selection by said selecting means of said unformatted one of said subdivisions upon a deter­mination by said determining means that said com­puter system is disk-idle, and (b) a need by said computer system for access to a formatted one of said subdivisions when said status information record maintaining means indicates that no formatted subdivisions exist.

Claim 3

The formatting system of claim 1 wherein said status information record maintaining means comprises means for storing a table on said medium, said table indicating the status of each of said subdivisions.

Claim 4

The formatting system of claim 1 wherein said disk-idle determining means comprises: means for measuring the passage of time; means for detecting when said computer system seeks access to said data storage medium; and means responsive to said time passage measuring means and to said access detecting means for making a determination of disk-idleness when a predetermined period of time passes without said computer system seeking access to said data storage medium.

Claim 5

The formatting system of claim 1 wherein: said data storage medium is a magneto-­optic data storage medium having magnetic domains aligned in one of two directions representing logical 0 and logical 1 and having a magnet for apply­ing a bias magnetic field, alignment of said magnetic domains being substantially fixed at room temperature, said magnetic domains aligning themselves with said bias magnetic field at temperatures above a threshold temperature, said data storage medium further having associated therewith means for generating a beam of coherent electromagnetic radiation for heating said medium to said threshold temperature for aligning said domains as desired and for reading data repre­sented by the alignment of said domains; and said formatting means comprises: mears for aligning said bias magnetic field in the direction representing logical 0; means for causing said coherent beam generating means to generate a first coherent beam of electromagnetic radiation focused on said selected one of said subdivisions for heating said selected one of said subdivisions above said threshold tempera­ture, thereby causing each magnetic domain in said subdivision to represent a logical 0, said subdivision thereby being erased; means for aligning said bias magnetic field in the direction representing logical 1; means for modulating said beam for writing a predetermined pattern of logical bits into said subdivision; means for causing said coherent beam generating means to generate a second coherent beam of electromagnetic radiation having a first, pre­determined polarization and for reflecting said second beam from said magnetic domains in said subdivision, said beam after reflection from one of said magnetic domains having a second polarization indicative of the alignment direction of said magnetic domain, for reading said subdivision; means for comparing data read from said subdivision with said predetermined pattern; means for recording in said status information record maintaining means that said sub­division is formatted if said data read from said subdivision compares with said predetermined pattern and for recording that said subdivision is bad if said data does not compare; and means for re-erasing said subdivision if said data compares with said predetermined pattern.

Claim 6

The formatting system of claim 4 wherein said formatting means further comprises means for assigning an alternate subdivision in place of a bad subdivision and for recording said assignment in said status information record maintaining means.

Claim 7

For use in a computer system having at least one high density data storage medium, said data storage medium having a large number of data storage subdivisions and requiring lengthy format times, a method for formatting said medium on a time-distributed basis, said formatting method comprising the steps of: maintaining a record of status infor­mation for each of said subdivisions, said status information including an indication of whether or not said subdivision has been formatted; determining when said computer system is disk-idle; selecting an unformatted one of said subdivisions when said computer system is disk-idle; and formatting an unformatted one of said subdivisions responsive to one of (a) selection of said unformatted one of said subdivisions upon a determination that said computer system is disk-idle, and (b) a need by said computer system for access to a formatted one of said subdivisions when said status information record indicates that no formatted sub­divisions exist.

Claim 8

For use in a computer system having at least one high density data storage medium, said data storage medium having a large number of data storage subdivisions and requiring lengthy format times, a method for formatting said medium on a time-distributed basis, said formatting method comprising the steps of: maintaining a record of status infor­mation for each of said subdivisions, said status information including an indication of whether or not said subdivision has been formatted; determining when said computer system is disk-idle; selecting an unformatted one of said subdivisions when said computer system is disk-idle; and formatting an unformatted one of said subdivisions responsive to one of (a) selection of said unformatted one of said subdivisions upon a determination that said computer system is disk-idle, and (b) a need by said computer system for access to a formatted one of said subdivisions when said status information record indicates that no formatted sub­divisions exist.

Claim 9

The formatting methods of claim 6 wherein said status information record maintaining step comprises storing a table on said medium, said table indicating the status of each of table on said medium, said table indicating the status of each of said subdivisions.

Claim 10

The formatting method of claim 6 wherein said disk-idle determining step comprises: measuring the passage of time; detecting when said computer system seeks access to said data storage medium; and making a determination of disk-idleness when a predetermined period of time passes without said computer system seeking access to said data storage medium.

Claim 11

The formatting method of claim 1 wherein: said data storage medium is a magneto-­optic data storage medium having magnetic domains aligned in one of two directions representing logical 0 and logical 1 and having a magnet for applying a bias magnetic field, alignment of said magnetic domains being substantially fixed at room temperature, said magnetic domains aligning themselves with said bias magnetic field at temperatures above a threshold temperature, said data storage medium further having associated therewith means for generating a beam of coherent electromagnetic radiation for heating said medium to said threshold temperature for aligning said domains as desired and for reading data repre­sented by the alignment of said domains; and said formatting step comprises: aligning said bias magnetic field in the direction representing logical 0; causing said coherent beam generating means to generate a first coherent beam of electro­magnetic radiation focused on said selected one of said subdivisions for heating said selected one of said subdivisions above said threshold temperature, thereby causing each magnetic domain in said sub­division to represent a logical 0, said subdivision thereby being erased; aligning said bias magnetic field in the direction representing logical 1; modulating said beam for writing a predetermined pattern of logical bits into said subdivision; causing said coherent beam generating means to generate a second coherent beam of electro­magnetic radiation having a first, predetermined polarization and for reflecting said second beam from said magnetic domains in said subdivision, said beam after reflection from one of said magnetic domains having a second polarization indicative of the alignment direction of said magnetic domain, for reading said subdivision; comparing data read from said sub­division with said predetermined pattern; recording in said status information record maintaining means that said subdivision is formatted if said data read from said subdivision compares with said predetermined pattern and recording that said subdivision is bad if said data does not compare; and re-erasing said subdivision if said data compares with said predetermined pattern.

Claim 12

The formatting method of claim 9 wherein said formatting step further comprises assigning an alternate subdivision in place of a bad subdivision and recording said assignment in said status informa­tion record.

Claim 13

In a computer system having at least one high density data storage medium, said data storage medium having a large number of data storage subdivisions ard requiring lengthy format times, a system for formatting said medium on a time-­distributed basis, said formatting system comprising: means for maintaining a record of status information for each of said subdivisions, said status information including an indication of whether or not said subdivision has been formatted; means for determining when said com­puter system is disk-idle; means responsive to said disk-idle determining means and to said status information record maintaining means for selecting an unformatted one of said subdivisions when said computer system is disk-idle; and means for formatting an unformatted one of said subdivisions responsive to selection by said selecting means of said unformatted one of said subdivisions upon a determination by said determining means that said computer system is disk-idle.

Claim 14

In a computer system having at least one high density data storage medium, said data storage medium having a large number of data storage subdivisions ard requiring lengthy format times, a system for formatting said medium on a time-­distributed basis, said formatting system comprising: means for maintaining a record of status information for each of said subdivisions, said status information including an indication of whether or not said subdivision has been formatted; means for determining when said com­puter system is disk-idle; means responsive to said disk-idle determining means and to said status information record maintaining means for selecting an unformatted one of said subdivisions when said computer system is disk-idle; and means for formatting an unformatted one of said subdivisions responsive to selection by said selecting means of said unformatted one of said subdivisions upon a determination by said determining means that said computer system is disk-idle.

Claim 15

The formatting system of claim 11 wherein said status information record maintaining means comprises means for storing a table on said medium, said table indicating the status of each of said subdivisions.

Claim 16

The formatting system of claim 11 wherein said disk-idle determining means comprises: means for measuring the passage of time; means for detecting when said computer system seeks access to said data storage medium; and means responsive to said time passage measuring means and to said access detecting means for making a determination of disk-idleness when a predetermined period of time passes without said computer system seeking access to said data storage medium.

Claim 17

The formatting system of claim 11 wherein: said data storage medium is a magneto-­optic data storage medium having magnetic domains aligned in one of two directions representing logical 0 and logical 1 and having a magnet for apply­ing a bias magnetic field, alignment of said magnetic domains being substantially fixed at room temperature, said magnetic domains aligning themselves with said bias magnetic field at temperatures above a threshold temperature, said data storage medium further having associated therewith means for generating a beam of coherent electromagnetic radiation for heating said medium to said threshold temperature for aligning said domains as desired and for reading data repre­sented by the alignment of said domains; and said formatting means comprises: means for aligning said bias magnetic field in the direction representing logical 0; means for causing said coherent beam generating means to generate a first coherent beam of electromagnetic radiation focused on said selected one of said subdivisions for heating said selected one of said subdivisions above said threshold tempera­ture, thereby causing each magnetic domain in said subdivision to represent a logical 0, said subdivision thereby being erased; means for aligning said bias magnetic field in the direction representing logical 1; means for modulating said beam for writing a predetermined pattern of logical bits into said subdivision; means for causing said coherent beam generating means to generate a second coherent beam of electromagnetic radiation having a first, pre­determined polarization and for reflecting said second beam from said magnetic domains in said subdivision, said beam after reflection from one of said magnetic domains having a second polarization indicative of the alignment direction of said magnetic domain, for reading said subdivision; means for comparing data read from said subdivision with said predetermined pattern; means for recording in said status information record maintaining means that said sub­division is formatted if said data read from said subdivision compares with said predetermined pattern and for recording that said subdivision is bad if said data does not compare; and means for re-erasing said subdivision if said data compares with said predetermined pattern.

Claim 18

The formatting system of claim 14 wherein said formatting means further comprises means for assigning an alternate subdivision in place of a bad subdivision and for recording said assignment in said status information record maintaining means.

Claim 19

For use in a computer system having at least one high density data storage medium, said data storage medium having a large number of data storage subdivisions and requiring lengthy format times, a method for formatting said medium on a time-distributed basis, said formatting method comprising the steps of: maintaining a record of status infor­mation for each of said subdivisions, said status information including an indication of whether or not said subdivision has been formatted; determining when said computer system is disk-idle; selecting an unformatted one of said subdivisions when said computer system is disk-idle; and formatting an unformatted one of said subdivisions responsive to selection of said unfor­matted one of said subdivisions upon a determination that said computer system is disk-idle.

Claim 20

For use in a computer system having at least one high density data storage medium, said data storage medium having a large number of data storage subdivisions and requiring lengthy format times, a method for formatting said medium on a time-distributed basis, said formatting method comprising the steps of: maintaining a record of status infor­mation for each of said subdivisions, said status information including an indication of whether or not said subdivision has been formatted; determining when said computer system is disk-idle; selecting an unformatted one of said subdivisions when said computer system is disk-idle; and formatting an unformatted one of said subdivisions responsive to selection of said unfor­matted one of said subdivisions upon a determination that said computer system is disk-idle.

Claim 21

The formatting method of claim 16 wherein said status information record maintaining step comprises storing a table on said medium, said table indicating the status of each of table on said medium, said table indicating the status of each of said subdivisions.

Claim 22

The formatting method of claim 16 wherein said disk-idle determining step comprises: measuring the passage of time; detecting when said computer system seeks access to said data storage medium; and making a determination of disk-­idleness when a predetermined period of time passes without said computer system seeking access to said data storage medium.

Claim 23

The formatting method of claim 11 wherein: said data storage medium is a magneto-­optic data storage medium having magnetic domains aligned in one of two directions representing logical 0 and logical 1 and having a magnet for applying a bias magnetic field, alignment of said magnetic domains being substantially fixed at room temperature, said magnetic domains aligning themselves with said bias magnetic field at temperatures above a threshold temperature, said data storage medium further having associated therewith means for generating a beam of coherent electromagnetic radiation for heating said medium to said threshold temperature for aligning said domains as desired and for reading data repre­sented by the alignment of said domains; and said formatting step comprises: aligning said bias magnetic field in the direction representing logical 0; causing said coherent beam generating means to generate a first coherent beam of electro­magnetic radiation focused on said selected one of said subdivisions for heating said selected one of said subdivisions above said threshold temperature, thereby causing each magnetic domain in said sub­division to represent a logical 0, said subdivision thereby being erased; aligning said bias magnetic field in the direction representing logical 1; modulating said beam for writing a predetermined pattern of logical bits into said subdivision; causing said coherent beam generating means to generate a second coherent beam of electro­magnetic radiation having a first, predetermined polarization and for reflecting said second beam from said magnetic domains in said subdivision, said beam after reflection from one of said magnetic domains having a second polarization indicative of the alignment direction of said magnetic domain, for reading said subdivision; comparing data read from said sub­division with said predetermined pattern; recording in said status information record maintaining means that said subdivision is formatted if said data read from said subdivision compares with said predetermined pattern and recording that said subdivision is bad if said data does not compare; and re-erasing said subdivision if said data compares with said predetermined pattern.

Claim 24

The formatting method of claim 19 wherein said formatting step further comprises assigning an alternate subdivision in place of a bad subdivision and recording said assignment in said status information record.

Claim 25

In a computer system having at least one high density data storage medium, said data storage medium having a large number of data storage subdivisions and requiring lengthy format times, a system for formatting said medium on a time-­distributed basis, said formatting system comprising: means for maintaining a record of status information for each of said subdivisions, said status information including an indication of whether or not said subdivision has been formatted; and means for formatting an unformatted one of said subdivisions responsive to a need by said computer system for access to a formatted one of said subdivisions when said status information record maintaining means indicates that no formatted subdivisions exist.

Claim 26

In a computer system having at least one high density data storage medium, said data storage medium having a large number of data storage subdivisions and requiring lengthy format times, a system for formatting said medium on a time-­distributed basis, said formatting system comprising: means for maintaining a record of status information for each of said subdivisions, said status information including an indication of whether or not said subdivision has been formatted; and means for formatting an unformatted one of said subdivisions responsive to a need by said computer system for access to a formatted one of said subdivisions when said status information record maintaining means indicates that no formatted subdivisions exist.

Claim 27

The formatting system of claim 21 wherein said status information record maintaining means comprises means for storing a table on said medium, said table indicating the status of each of said subdivisions.

Claim 28

The formatting system of claim 21 wherein said disk-idle determining means comprises: means for measuring the passage of time; means for detecting when said computer systems seeks access to said data storage medium; and means responsive to said time passage measuring means and to said access detecting mears for making a determination of disk-idleness when a predetermined period of time passes without said computer system seeking access to said data storage medium.

Claim 29

The formatting system of claim 21 wherein: said data storage medium is a magneto-­optic data storage medium having magnetic domains aligned in one of two directions representing logical 0 and logical 1 and having a magnet for apply­ing a bias magnetic field, alignment of said magnetic domains being substantially fixed at room temperature, said magnetic domains aligning themselves with said bias magnetic field at temperatures above a threshold temperature, said data storage medium further having associated therewith means for generating a beam of coherent electromagnetic radiation for heating said medium to said threshold temperature for aligning said domains as desired and for reading data repre­sented by the alignment of said domains; and said formatting means comprises: means for aligning said bias magnetic field in the direction representing logical 0; means for causing said coherent beam generating means to generate a first coherent beam of electromagnetic radiation focused on said selected one of said subdivisions for heating said selected one of said subdivisions above said threshold tempera­ture, thereby causing each magnetic domain in said subdivision to represent a logical 0, said subdivision thereby being erased; means for aligning said bias magnetic field in the direction representing logical 1; means for modulating said beam for writing a predetermined pattern of logical bits into said subdivision; means for causing said coherent beam generating means to generate a second coherent beam of electromagnetic radiation having a first, pre­determined polarization and for reflecting said second beam from said magnetic domains in said subdivision, said beam after reflection from one of said magnetic domains having a second polarization indicative of the alignment direction of said magnetic domain, for reading said subdivision; means for comparing data read from said subdivision with said predetermined pattern; means for recording in said status information record maintaining means that said sub­division is formatted if said data read from said subdivision compares with said predetermined pattern and for recording that said subdivision is bad if said data does not compare; and means for re-erasing said subdivision if said data compares with said predetermined pattern.

Claim 30

The formatting system of claim 24 wherein said formatting means further comprises means for assigning an alternate subdivision in place of a bad subdivision and for recording said assignment in said status information record maintaining means.

Claim 31

For use in a computer systems having at least one high density data storage medium, said data storage medium having a large number of data storage subdivisions and requiring lengthy format times, a method for formatting said medium on a time-distributed basis, said formatting method comprising the steps of: maintaining a record of status infor­mation for each of said subdivisions, said status information including an indication of whether or not said subdivision has been formatted; and formatting an unformatted one of said subdivisions responsive to a need by said computer system for access to a formatted one of said sub- divisions when said status information record indicates that no formatted subdivisions exist.

Claim 32

For use in a computer systems having at least one high density data storage medium, said data storage medium having a large number of data storage subdivisions and requiring lengthy format times, a method for formatting said medium on a time-distributed basis, said formatting method comprising the steps of: maintaining a record of status infor­mation for each of said subdivisions, said status information including an indication of whether or not said subdivision has been formatted; and formatting an unformatted one of said subdivisions responsive to a need by said computer system for access to a formatted one of said sub- divisions when said status information record indicates that no formatted subdivisions exist.

Claim 33

The formatting method of claim 26 wherein said status information record maintaining step comprises storing a table on said medium, said table indicating the status of each of table on said medium, said table indicating the status of each of said subdivisions.

Claim 34

The formatting method of claim 21 wherein: said data storage medium is a magneto-­optic data storage medium having magnetic domains aligned in one of two directions representing logical 0 and logical 1 and having a magnet for applying a bias magnetic field, alignment of said magnetic domains being substantially fixed at room temperature, said magnetic domains aligning themselves with said bias magnetic field at temperatures above a threshold temperature, said data storage medium further having associated therewith means for generating a beam of coherent electromagnetic radiation for heating said medium to said threshold temperature for aligning said domains as desired and for reading data repre­sented by the alignment of said domains; and said formatting step comprises: aligning said bias magnetic field in the direction representing logical 0; causing said coherent beam generating means to generate a first coherent beam of electro­magnetic radiation focused on said selected one of said subdivisions for heating said selected one of solid subdivisions above said threshold temperature, thereby causing each magnetic domains in said sub­division to represent a logical 0, said subdivision thereby being erased; aligning said bias magnetic field in the direction representing logical 1; modulating said beam for writing a predetermined pattern of logical bits into said subdivision; causing said coherent beam generating means to generate a second coherent beam of electro-­magnetic radiation having a first, predetermined polarization and for reflecting said second beam from said magnetic domains in said subdivision, said beam after reflection from one of said magnetic domains having a second polarization indicative of the alignment direction of said magnetic domain, for reading said subdivision; comparing data read from said sub­division with said predetermined pattern; recording in said status information record maintaining means that said subdivision is formatted if said data read from said subdivision compares with said predetermined pattern and recording that said subdivision is bad if said data does not compare; and re-erasing said subdivision if said data compares with said predetermined pattern.

Claim 35

The formatting method of claim 28 wherein said formatting step further comprises assigning an alternate subdivision in place of a bad subdivision and recording said assignment in said status information record.

Claim 36

In a computer system having a main memory and having a magneto-optical data storage medium of a type having data subdivisions which must be erased before they can be written on, a system for erasing previously used data subdivisions before they are needed again, said erasing system comprising: means for maintaining a table of previously-used, formatted, erased data subsidivisions; means for maintaining a list of previously-used formatted data subdivisions to be erased; means for determining when said com­puter system is disk-idle; means responsive to said disk-idle determining means and to said list maintaining means for selecting from said list one of said previously-­used subdivisions to be erased when said computer system is disk-idle; and means for erasing one of said sub­divisions responsive to one of (a) selection by said selecting means of said one of said subdivisions upon a determination by said determining means that said computer system is disk-idle, and (b) a need by said computer system for access to one of said sub­divisions when said table maintaining mears indicates that no erased subdivisions exist.

Claim 37

In a computer system having a main memory and having a magneto-optical data storage medium of a type having data subdivisions which must be erased before they can be written on, a system for erasing previously used data subdivisions before they are needed again, said erasing system comprising: means for maintaining a table of previously-used, formatted, erased data subsidivisions; means for maintaining a list of previously-used formatted data subdivisions to be erased; means for determining when said com­puter system is disk-idle; means responsive to said disk-idle determining means and to said list maintaining means for selecting from said list one of said previously-­used subdivisions to be erased when said computer system is disk-idle; and means for erasing one of said sub­divisions responsive to one of (a) selection by said selecting means of said one of said subdivisions upon a determination by said determining means that said computer system is disk-idle, and (b) a need by said computer system for access to one of said sub­divisions when said table maintaining mears indicates that no erased subdivisions exist.

Claim 38

The erasing system of claim 30 wherein said table maintaining means comprises means for storing a table on said medium, said table indicating the status of each of said subdivisions.

Claim 39

The erasing system of claim 30 wherein said list maintaining means comprises means for storing in said main memory a list of subdivisions to be erased.

Claim 40

The erasing system of claim 30 wherein said disk-idle determining means comprises: means for measuring the passage of time; mears for detecting when said computer system seeks access to said data storage medium; and means responsive to said time passage measuring means and to said access detecting means for making a determination of disk-idleness when a predetermined period of time passes without said computer system seeking access to said data storage medium.

Claim 41

The erasing system of claim 30 wherein: said magneto-optic data storage medium has magnetic domains aligned in one of two directions representing logical 0 and logical 1 and having a magnet for applying a bias magnetic field, alignment of said magnetic domains being substantially fixed at room temperature, said magnetic domains aligning themselves with said bias magnetic field at tempera­tures above a threshold temperature, said data storage medium further having associated therewith means for generating a beam of coherent electromagnetic radiation for heating said medium to said threshold temperature for aligning said domains as desired; and said erasing means comprises: means for aligning said bias magnetic field in the direction representing logical 0; means for causing said coherent beam generating means to generate a coherent beam of electromagnetic radiation focused on said selected one of said subdivisions for heating said selected one of said subdivisions above said threshold tempera­ture, thereby causing each magnetic domain in said subdivision to represent a logical 0, said subdivision thereby being erased; and means for recording in said list main­taining means that said subdivision is erased.

Claim 42

The erasing system of claim 30 wherein said list maintaining means comprises mears for adding to said list, whenever a file is deleted, those ones of said subdivisions used by said file.

Claim 43

For use in a computer system having a main memory and having a magneto-optical data storage medium of a type having data subdivisions which must be erased before they can be written on, a method for erasing previously used data subdivisions before they are needed again, said erasing method comprising the steps of: maintaining a table of previously-used, formatted, erased data subdivisions; maintaining a list of previously-used formatted data subdivisions to be erased; determining when said computer system is disk-idle; selecting one of said previously-used subdivisions to be erased when said computer system is disk-idle; and erasing one of said subdivisions responsive to one of (a) selection by said selecting step of said one of said subdivisions upon a deter­mination that said computer system is disk-idle, and (b) a need by said computer system for access to one of said subdivisions when no erased subdivisions exist.

Claim 44

For use in a computer system having a main memory and having a magneto-optical data storage medium of a type having data subdivisions which must be erased before they can be written on, a method for erasing previously used data subdivisions before they are needed again, said erasing method comprising the steps of: maintaining a table of previously-used, formatted, erased data subdivisions; maintaining a list of previously-used formatted data subdivisions to be erased; determining when said computer system is disk-idle; selecting one of said previously-used subdivisions to be erased when said computer system is disk-idle; and erasing one of said subdivisions responsive to one of (a) selection by said selecting step of said one of said subdivisions upon a deter­mination that said computer system is disk-idle, and (b) a need by said computer system for access to one of said subdivisions when no erased subdivisions exist.

Claim 45

The erasing method of claim 36 wherein said table maintaining step comprises storing a table on said medium, said table indicating the status of each of said subdivisions.

Claim 46

The erasing method of claim 36 wherein said list maintaining step comprises storing in said main memory a list of subdivisions to be erased.

Claim 47

The erasing method of claim 36 where­in said disk-idle determining step comprises: measuring the passage of time; detecting when said computer system seeks access to said data storage medium; and making a determination of disk-idleness when a predetermined period of time passes without said computer system seeking access to said data storage medium.

Claim 48

The erasing method of claim 36 wherein said list maintaining step comprises means for adding to said list, whenever a file is deleted, those ones of said subdivisions used by said file.

Claim 49

The erasing method of claim 36 wherein: said magneto-optic data storage medium has magnetic domains aligned in one of two directions representing logical 0 and logical 1 and having a magnet for applying a bias magnetic field, alignment of said magnetic domains being substantially fixed at room temperature, said magnetic domains aligning themselves with said bias magnetic field at tempera­tures above a threshold temperature, said data storage medium further having associated therewith means for generating a beam of coherent electromagnetic radia­tion for heating said medium to said threshold temperature for aligning said domains as desired; and said erasing step comprises: aligning said bias magnetic field in the direction representing logical 0; causing said coherent beam generating means to generate a coherent beam of electromagnetic radiation focused on said selected one of said sub­divisions for heating said selected one of said subdivisions above said threshold temperature, thereby causing each magnetic domain in said subdivision to represent a logical 0, said subdivision thereby being erased; and recording in said list that said sub­division is erased.

Claim 50

In a computer system having a main memory and having a magneto-optical data storage medium of a type having data subdivisions which must be erased before they can be written on, a system for erasing previously used data subdivisions before they are needed again, said erasing system comprising: means for maintaining a list of previously-used formatted data subdivisions to be erased; means for determining when said com­puter system is disk-idle; means responsive to said disk-idle determining means and to said list maintaining means for selecting one of said previously-used subdivisions to be erased when said computer system is disk-idle; and means for erasing one of said sub­divisions responsive to selection by said selecting means of said one of said subdivisions upon a deter­mination by said determining means that said computer system is disk-idle.

Claim 51

In a computer system having a main memory and having a magneto-optical data storage medium of a type having data subdivisions which must be erased before they can be written on, a system for erasing previously used data subdivisions before they are needed again, said erasing system comprising: means for maintaining a list of previously-used formatted data subdivisions to be erased; means for determining when said com­puter system is disk-idle; means responsive to said disk-idle determining means and to said list maintaining means for selecting one of said previously-used subdivisions to be erased when said computer system is disk-idle; and means for erasing one of said sub­divisions responsive to selection by said selecting means of said one of said subdivisions upon a deter­mination by said determining means that said computer system is disk-idle.

Claim 52

The erasing system of claim 42 wherein said list maintaining means comprises means for storing in said main memory a list of subdivisions to be erased.

Claim 53

The erasing system of claim 42 where­in said disk-idle determining means comprises: means for measuring the passage of time; means for detecting when said computer system seeks access to said data storage medium; and means responsive to said time passage measuring means and to said access detecting means for making a determination of disk-idleness when a predetermined period of time passes without said computer system seeking access to said data storage medium.

Claim 54

The erasing system of claim 42 wherein: said magneto-optic data storage medium has magnetic domains aligned in one of two directions representing logical 0 and logical 1 and having a magnet for applying a bias magnetic field, alignment of said magnetic domains being substantially fixed at room temperature, said magnetic domains aligning themselves with said bias magnetic field at tempera­tures above a threshold temperature, said data storage medium further having associated therewith mears for generating a beam of coherent electromagnetic radiation for heating said medium to said threshold temperature for aligning said domains as desired; and said erasing means comprises: means for aligning said bias magnetic field in the direction representing logical 0; means for causing said coherent beam generating means to generate a coherent beam of electromagnetic radiation focused on said selected one of said subdivisions for heating said selected one of said subdivisions above said threshold tempera­ture, thereby causing each magnetic domain in said subdivision to represent a logical 0, said subdivision thereby being erased; and means for recording in said list main­taining means that said subdivision is erased.

Claim 55

The erasing system of claim 42 wherein said list maintaining means comprises means for adding to said list, whenever a file is deleted, those ones of said subdivisions used by said file.

Claim 56

For use in a computer system having a main memory and having a magneto-optical data storage medium of a type having data subdivisions which must be erased before they can be written on, a method for erasing previously used data subdivisions before they are needed again, said erasing method comprising the steps of: maintaining a list of previously-used formatted data subdivisions to be erased; determining when said computer system is disk-idle; selecting one of said previously-used subdivisions to be erased when said computer system is disk-idle; and erasing one of said subdivisions responsive to selection by said selecting step of said one of said subdivisions upon a determination that said computer system is disk-idle.

Claim 57

For use in a computer system having a main memory and having a magneto-optical data storage medium of a type having data subdivisions which must be erased before they can be written on, a method for erasing previously used data subdivisions before they are needed again, said erasing method comprising the steps of: maintaining a list of previously-used formatted data subdivisions to be erased; determining when said computer system is disk-idle; selecting one of said previously-used subdivisions to be erased when said computer system is disk-idle; and erasing one of said subdivisions responsive to selection by said selecting step of said one of said subdivisions upon a determination that said computer system is disk-idle.

Claim 58

The erasing method of claim 47 wherein said list maintaining step comprising storing in said main memory a list of subdivisions to be erased.

Claim 59

The erasing method of claim 47 wherein said disk-idle determining step comprises: measuring the passage of time; detecting when said computer system seeks access to said data storage medium; and making a determination of disk-idleness when a predetermined period of time passes without said computer system seeking access to said data storage medium.

Claim 60

The erasing method of claim 47 wherein said list maintaining means comprises means for adding to said list, whenever a file is deleted, those ones of said subdivisions used by said file.

Claim 61

The erasing method of claim 47 wherein: said magneto-optic data storage medium has magnetic domains aligned in one of two directions representing logical 0 and logical 1 and having a magnet for applying a bias magnetic field, alignment of said magnetic domains being substantially fixed at room temperature, said magnetic domains aligning themselves with said bias magnetic field at tempera­tures above a threshold temperature, said data storage medium further having associated therewith means for generating a beam of coherent electromagnetic radia­tion for heating said medium to said threshold temperature for aligning said domains as desired; and said erasing step comprises: aligning said bias magnetic field in the direction representing logical 0; causing said coherent beam generating means to generate a coherent beam of electromagnetic radiation focused on said selected one of said sub­divisions for heating said selected one of said subdivisions above said threshold temperature, thereby causing each magnetic domain in said subdivision to represent a logical 0, said subdivision thereby being erased; and recording in said list that said sub­division is erased.

Claim 62

In a computer system having a magneto-­optical data storage medium of a type having data subdivisions which must be erased before they can be written on, a system for erasing previously used data subdivisions before they are needed again, said erasing system comprising: means for maintaining a table of previously-used, formatted, erased data subdivisions; means for erasing one of said sub­divisions responsive to a need by said computer system for access to one of said subdivisions when said table maintaining means indicates that no erased subdivisions exist.

Claim 63

In a computer system having a magneto-­optical data storage medium of a type having data subdivisions which must be erased before they can be written on, a system for erasing previously used data subdivisions before they are needed again, said erasing system comprising: means for maintaining a table of previously-used, formatted, erased data subdivisions; means for erasing one of said sub­divisions responsive to a need by said computer system for access to one of said subdivisions when said table maintaining means indicates that no erased subdivisions exist.

Claim 64

The erasing system of claim 50 wherein said table maintaining means comprises means for storing a table on said medium, said table indicating the status of each of said subdivisions.

Claim 65

The erasing system of claim 52 wherein: said magneto-optic data storage medium has magnetic domains aligned in one of two directions representing logical 0 and logical 1 and having a magnet for applying a bias magnetic field, alignment of said magnetic domains being substantially fixed at room temperature, said magnetic domains aligning themselves with said bias magnetic field at tempera­tures above a threshold temperature, said data storage medium further having associated therewith means for generating a beam of coherent electromagnetic radiation for heating said medium to said threshold temperature for aligning said domains as desired; and said erasing means comprises: means for aligning said bias magnetic field in the direction representing logical 0; means for causing said coherent beam generating means to generate a coherent beam of electromagnetic radiation focused on said selected one of said subdivisions for heating said selected one of said subdivisions above said threshold tempera­ture, thereby causing each magnetic domain in said subdivision to represent a logical 0, said subdivision thereby being erased; and means for recording in said list main­taining means that said subdivision is erased.

Claim 66

The erasing system of claim 52 wherein said table maintaining means comprises means for updating said table whenever a subdivision is erased.

Claim 67

For use in a computer system having a magneto-optical data storage medium of a type having data subdivisions which must be erased before they can be written on, a method for erasing previously used data subdivisions before they are needed again, said erasing method comprising the steps of: maintaining a table of previously-used, formatted, erased data subdivisions; and erasing one of said subdivisions responsive to a need by said computer system for access to one of said subdivisions when no erased subdivisions exist.

Claim 68

For use in a computer system having a magneto-optical data storage medium of a type having data subdivisions which must be erased before they can be written on, a method for erasing previously used data subdivisions before they are needed again, said erasing method comprising the steps of: maintaining a table of previously-used, formatted, erased data subdivisions; and erasing one of said subdivisions responsive to a need by said computer system for access to one of said subdivisions when no erased subdivisions exist.

Claim 69

The erasing methods of claim 56 wherein said table maintaining step comprises storing a table on said medium, said table indicating the status of each of said subdivisions.

Claim 70

The erasing method of claim 56 wherein said table maintaining step comprises means for updating said table whenever a subdivision is erased.

Claim 71

The erasing method of claim 56 wherein: said magneto-optic data storage medium has magnetic domains aligned in one of two directions representing logical 0 and logical 1 and having a magnet for applying a bias magnetic field, alignment of said magnetic domains being substantially fixed at room temperature, said magnetic domains aligning themselves with said bias magnetic field at tempera­tures above a threshold temperature, said data storage medium further having associated therewith means for generating a beam of coherent electromagnetic radia­tion for heating said medium to said threshold temperature for aligning said domains as desired; and said erasing step comprises: aligning said bias magnetic field in the direction representing logical 0; causing said coherent beam generating means to generate a coherent beam of electromagnetic radiation focused on said selected one of said sub­divisions for heating said selected one of said subdivisions above said threshold temperature, thereby causing each magnetic domain in said subdivision to represent a logical 0, said subdivision thereby being erased; and recording in said list that said sub­division is erased.