Method for loading data on a tape at a center of the tape, and a tape for implementing the method

In a method for writing data on a data carrier tape, a central region of the tape is positioned adjacent a data recording head, data are supplied to the data recording head, and data are transferred from the data recording head to the tape, beginning at the center region of the tape, while moving the tape along a longitudinal direction of the tape. The tape transport direction can be alternatingly reversed at the opposite ends of the tape so data are recorded successively on adjacent data recording tracks on the tape, with data transfer being inhibited each time the center region of the tape passes by the data recording head. A data carrier tape for implementing the method has a hole pattern in the central region of the tape, which identifies the central region of the tape to allow positioning of the tape at the central region, and to allow recognition of the central region for inhibiting data transfer when the central region of the tape is adjacent the data recording head.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention is directed to a method for loading data on a tape,
 such as a magnetic tape, as well as to a tape for implementing the method,
 such as a tape having a hole pattern therein.
 2. Description of the Prior Art
 It is known to write data on a strip-like data carrier, such as a magnetic
 tape, in a controlled sequence and at controlled locations on the tape by
 the execution of a bit output program. Typically, data are written in a
 number of parallel tracks on the tape, the tracks proceeding parallel to
 the tape transport direction, which is along the longitudinal (longest)
 direction of the tape. The tape can be transported bidirectionally during
 the execution of the bit output program so that the data can be written on
 the tape from one end to the other, while the tape is moving in a first
 direction, and then the tape movement direction is reversed so that data
 are written in a parallel track while the tape moves from the second end
 back to the first end. The first end is usually referred to as the
 "beginning of tape", or BOT, and the opposite end is referred to as the
 "end of tape", or EOT.
 During the execution of the bit output program, the tape is moved extremely
 fast, and therefore the tape transport system must have some way of
 recognizing BOT and EOT, as well as having some kind of indication when
 either BOT or EOT is approaching. For this purpose, a standardized system
 of tape holes or tape hole patterns has been devised, which is employed in
 high speed data reading and writing systems. Accordingly, a BOT marker is
 provided at one end of a conventional tape, which consists of several
 pairs, often four pairs, of holes which are spaced along the longitudinal
 direction of the tape, near the physical beginning edge of the tape. The
 holes in each pair are substantially vertically aligned in a direction
 perpendicular to the longitudinal direction. The pairs of holes are
 respectively designated with numbers, so that if four such pairs are
 employed, they will be designated BOT1, BOT2, BOT3 and BOT4.
 The tape drive is provided with a light barrier system, i.e., a light
 emitter and a light receiver, so that as the tape passes between the light
 emitter and light receiver, the presence of the holes is noted and the
 drive is controlled accordingly.
 The tape is also typically provided with a tape identification (tape ID)
 and/or cartridge identification (cartridge ID) hole pattern between BOT1
 and BOT2. This hole pattern provides identification regarding the tape or
 cartridge itself, such as file information, information about the data to
 be stored thereon, identification of the tape manufacturer or tape type,
 or identification regarding a drive or drives with which the tape or
 cartridge is compatible.
 According to the standard, the beginning of tape hole pair designated BOT1
 will be the farthest from the physical beginning edge of the tape, and
 BOT4 will be closest to the physical edge. At some point proceeding in a
 direction away from the physical beginning of the tape, beyond BOT1, a
 load point (LP) marker hole will be provided, which is a single hole in
 the tape that indicates the start of the useable recording area when the
 tape transport motion is in the direction conventionally designated as the
 "forward" direction. Data are stored on the tape magnetically only after
 the load point marker is traversed.
 At the opposite end of the tape, a series of single holes is provided in
 the tape to indicate the end of the tape. These single holes will usually
 be spaced from the longitudinal edge of the tape at the same distance as
 one of the holes in the hole pairs identifying the beginning of the tape.
 If four such end of tape identifiers or markers are employed, they will be
 designated EOT1, EOT2, EOT3 and EOT4, with EOT4 being closest to the
 physical end of the tape and EOT1 being farthest from the physical end of
 the tape. Preceding EOT1, at some point farther from the physical end of
 the tape than EOT1, is an early warning (EW) marker, which is a hole
 disposed at approximately the same location from the longitudinal edge of
 the tape as the load point marker. This hole provides an early indication
 to the drive of the approaching end of the tape, and is usually the point
 where writing of data onto the tape ceases when the tape is moving in the
 forward direction.
 For bidirectional loading of data onto a tape, wherein the tape moves
 rapidly back and forth between the (arbitrarily) designated beginning of
 tape and end of tape, when the tape moves in a direction opposite to the
 arbitrarily designated "forward" direction, the early warning marker can
 then serve as the load point marker to begin loading of data when the tape
 is moving opposite the forward direction, and the aforementioned load
 point marker can then serve as the early warning marker to indicate the
 approaching beginning of the tape and the necessity of undertaking a
 direction reversal.
 In conventional loading systems, as noted above, data loading takes place
 by starting with a data track, typically near the longitudinal edge of the
 tape, at the point at which the LP marker after BOT1 is reached, and the
 tape is transported in the "forward" direction until data loading stops at
 the early warning point, whereupon a reversal of the tape transport
 direction takes place and data are then loaded on a parallel track,
 typically adjacent to the just-written track, as the tape moves back in
 the opposite direction. Data loading then ceases when the load point
 marker preceding BOT1 is reached, and a direction reversal again takes
 place. This sequence is repeated until all tracks on the tape are filled,
 or until no more data are available for writing onto the tape.
 If all of the data stored on a tape are to be read therefrom, the same
 procedure is repeated with the magnetic head operating in a read mode,
 rather than a write mode. If only a portion of the data are to be read, or
 if designated data are to be read, a search program can be undertaken to
 try to position the tape as quickly as possible to read the desired data
 without having to sequence through the entirety of the data stored on the
 tape. Depending on where the tape happens to be positioned on the spools
 along its longitudinal length, however, a considerable length of tape may
 have to be traversed before the location is reached at which the desired
 data are stored. For example, if the tape at the conclusion of a preceding
 operation happens to be positioned so that a part of the tape close to the
 beginning of the tape is adjacent the read/write head, but data are
 desired to be read which are located near the end of the tape, the tape
 must be transported through virtually its entire length before the data
 can be accessed. If this occurs multiple times during multiple data access
 operations, this can result in considerable delays in gaining access to
 the data, and moreover requires that the tape and tape transport system be
 operated at a high speed during which no direct benefit is being obtained,
 i.e., no data are being read.
 SUMMARY OF THE INVENTION
 It is an object of the present invention to provide a method for writing
 data on a tape-like data carrier, such as a magnetic tape, which allows
 more rapid access to the recorded data than conventional data writing
 methods.
 It is a further object of the present invention to provide a tape on which
 data can be written in a manner which provides more rapid access to the
 data on the tape than is the case for conventional tapes.
 The above object is achieved in accordance with the principles of the
 present invention in a method for writing data on a data carrier tape
 wherein the writing of data begins at a location at the center of the
 tape, and proceeds along tracks in "forward" and "reverse" directions
 between the center of the tape and the conventionally designated beginning
 of tape and end of tape.
 The above object is also achieved in a data carrier tape, such as a
 magnetic tape, having an appropriate hole pattern arrangement disposed
 along a length of a tape at the center of the tape, for providing the
 necessary commands and indicators to a conventional optical reader system
 in a drive, so as to allow the aforementioned inventive method to be
 implemented.
 As used herein, the term "center" or "center of the tape" does not
 necessarily mean the exact geometric center of the tape between the
 physical tape beginning and the physical tape end. The terms "center" and
 "center of tape" as used herein refer to a region which is generally
 located approximately midway between the hole patterns which are
 conventionally present at the beginning of the tape and the end of the
 tape, i.e., approximately in a middle region of the data-recording region
 of the data carrier tape. As will be apparent from the discussion below,
 the time-saving advantages for access to the data stored on the tape are
 maximized when the region designated as "center of the tape" encompasses
 the geometrical center or midpoint of the tape, however, time-saving
 advantages can still be obtained if the region designated "center of the
 tape" is arbitrarily selected at any location which is spaced a
 significant distance from the physical ends of the data carrier tape.
 The access time for reading data stored on a tape, on which the data are
 recorded in accordance with the inventive method, can be even further
 improved in an embodiment of the method wherein the data-recording regions
 on opposite sides of the location designated as the center of the tape
 (i.e., the region between the designated center of tape region and the
 beginning of tape region, and the region between the designated center of
 tape region and the end of tape region), are further divided into data
 recording sections. Within each data recording section, the tape is
 bidirectionally transported while data are written on all parallel tracks
 in that section, and only after the data tracks for a given section are
 completely filled does data recording then move to another section. Since
 the sections occupy comparatively shorter lengths of the overall data
 carrier tape length, a data search can be conducted within each section
 very quickly, compared to searching or moving along the entire tape, as
 well as compared to searching or moving within only one-half of the tape
 length.
 In a data carrier tape designed for implementing the inventive method, a
 series of hole pairs, similar to those conventionally used at the
 beginning of the tape, are punched in the tape, in order to allow the
 optical system in the tape drive to identify the region which has been
 designated as the center of the tape, in order to initiate appropriate
 control commands for operating the drive. A hole pattern representing a
 tape ID or cartridge ID is disposed between two of the pairs of the center
 of tape marker holes. On one side of the last of the center of tape marker
 hole pairs, a hole is punched in the tape designating a load point,
 following which data can be recorded onto the data carrier tape. At the
 opposite side of the center of tape markers, and spaced therefrom, an
 early warning hole is provided. Since data recording on the tape
 constructed in accordance with the invention is necessarily accomplished
 bidirectionally, the designation of these outlying holes as a load point
 marker and an early warning marker, respectively, is somewhat arbitrary
 because depending on the tape transport direction, the early warning
 marker can serve as a load point marker, and the load point marker can
 serve as an early warning marker.
 In an embodiment of the tape employing four pairs of center of tape marker
 holes, the total length of the tape occupied between the early warning
 marker and the load point marker associated with the center of the tape
 markers is 196 inches. In an embodiment wherein more data carrier tape
 area is made available for data recording, only two pairs of center of
 tape marker holes are employed, with a tape or cartridge ID hole pattern
 therebetween, and an early warning marker hole on an opposite side of one
 center of tape marker pair, and a load point marker hole on an opposite
 side of the other center of tape marker pair. In this embodiment, the tape
 length between the early warning marker and the load point marker is only
 24 inches, thereby freeing a considerable area of the data carrier tape
 for data recording.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
 FIG. 1 schematically illustrates an arrangement for reading and writing
 data (transferring data) to and from a tape-like data carrier. The
 apparatus (except for the tape) is conventional in structure, but it is
 operated unconventionally, in accordance with the principles of the
 inventive method.
 The tape-like data carrier is shown in the embodiment of FIG. 1 as being a
 magnetic tape 1, however, the inventive method can be employed in any type
 of elongated, tape-like data carrier. The magnetic tape 1 has opposite
 physical ends, with a region adjacent one of those physical ends being
 designated as the beginning of tape region BOT, and a region adjacent the
 opposite physical end of the tape 1 being designated as the end of tape
 region EOT. The region BOT and the region EOT respectively contain
 conventional hole patterns of the type described above.
 The magnetic tape 1 also has a region designated as the center of tape
 region COT. This region can be arbitrarily located at any significant
 distance between the BOT region and the EOT region, however, as described
 below the reduction in access to data time is maximized in accordance with
 the inventive method if the COT region encompasses the geometrical center
 or midpoint of the magnetic tape 1. The magnetic tape 1 is moved in a
 conventional manner by a conventional tape drive system in opposite tape
 transport directions, as indicated by the double arrow.
 Data transfer takes place relative to the magnetic tape 1 by means of a
 read/write head 2, which is connected to a read/write control 3. Data to
 be written on the magnetic tape 1 are supplied from a data source for, and
 data read from the magnetic tape 1 can be supplied to the data source 4
 for storage therein, or to some other location for some other purpose.
 The center of tape region COT for a first embodiment of a magnetic tape 1
 for implementing the inventive method is shown in FIG. 2. This embodiment
 employs four pairs of center of tape marker holes, COT1, COT2, COT3 and
 COT4. A tape ID hole pattern is disposed between two of these center of
 tape marker pairs, such as between COT1 and COT2. The pattern of the tape
 ID informs the drive that the tape, or tape cartridge, is of a type for
 which a loading from center procedure should be implemented. An identical
 tape ID can be disposed at the conventional locations at the BOT region
 and EOT region so that if the tape at the beginning of a read or write
 operation is located with the BOT region or the EOT region adjacent the
 read/write head, the drive will be informed that the tape should be
 advanced or reversed until the center of tape region COT is in front of
 the read/write head 2, before beginning the read or write procedure. Less
 preferably, there could simply be no tape ID hole pattern at either the
 BOT region or the EOT region, and if the drive then recognizes a BOT
 region without a tape ID pattern or an EOT region without a tape ID
 pattern, the drive then "defaults" to cause the tape to be moved to
 position the COT region in front of the read/write head 2.
 As can be seen in FIG. 2, the hole pairs COT1 through COT4 resemble the
 conventional hole pairs used to designate BOT. If the distance between the
 tape holes and the number of holes in FIG. 2 are maintained exactly as in
 conventional tapes for the BOT designation, the total distance of the
 conventional BOT designation area is 136 inches. This would then also be
 the total distance between COT4 and a new loading point marker hole LP2,
 which identifies the location at which data recording can start following
 identification of the center of the tape. In conventional tapes, the early
 warning hole is placed 60 inches in front of the first-encountered BOT
 hole pair or the last-encountered EOT hole. If this conventional distance
 is adhered to in the embodiment of FIG. 2, this means the total distance
 between the new early warning hole EW1 and the new loading point marker
 hole LP2, will be a total of 196 inches, or 16.33 feet. On a conventional
 tape, this area would normally be available for data recording. For a tape
 having a longitudinal length of 1500 feet, the capacity loss will
 therefore be (16.33/1500).multidot.100%=1.09%.
 The length of the hole patterns in the COT region, however, can be made
 much shorter than conventional pattern arrangements, because at that
 location on the tape there is no risk of running out of tape, i.e.,
 inadvertently reaching the physical edge of the tape. The minimum length
 of the COT region will be determined primarily by how quickly and
 accurately the drive for which the tape is intended to be used can stop
 between the COT hole pairs which are present. There are commercial drives
 available which, if being operated at 30 ips, require approximately 4
 inches to stop. Moreover, the distance between COT1 and LP2 can be set
 extremely small, or may even be 0. The distance from EW1 to the closest
 center of tape hole pair must be maintained large enough to allow proper
 termination of the recording, once EW1 is traversed and recognized. In
 most drives, a distance of 4 inches will be enough to allow for proper
 termination of the recording.
 The embodiment of FIG. 3 shows a tape drive for implementing the inventive
 method which embodies the above considerations. In this embodiment, only
 two center of tape marker pairs COT1 and COT2 are provided, and the total
 length of the marker hole region at the center of the tape is thereby
 reduced to approximately 24 inches, or 2 feet. The capacity loss is then
 only 0.13%.
 One embodiment for conducting the inventive method is shown in FIG. 4.
 Before beginning a data writing operation, i.e., at a beginning of the
 execution of the bit output program, the tape 1 is positioned with the COT
 region in front of the read/write head 2, as described above. The bit
 output program then begins at location BOP (beginning of program) as shown
 in FIG. 4. The magnetic tape is repeatedly advanced and reversed in the
 direction of the arrows while only a relatively small longitudinal section
 of the tape is filled with data in adjacent, parallel tracks. This section
 in FIG. 4 is arbitrarily designated as section I. The BOP location will
 preferably be at a beginning of the penultimate bottom track (i.e., one
 recording track above the bottommost track in the section). After filling
 the penultimate data track (i.e., the data track immediately adjacent and
 below the uppermost data track) in section I, the drive recognizes that
 this has occurred, by counting the number of tracks that had been filled,
 and repositions the tape 1 so that the read/write head is able to enter
 data into another section, arbitrarily designated section II. Since the
 tape 1 is merely moved without vertically repositioning the read/write
 head 2, section II begins to be filled with the penultimate upper data
 track, and after the penultimate upper data track in section II is filled
 with data, the read/write head 2 is moved downwardly by a number of track
 heights (widths) to the track immediately above the bottommost track (the
 penultimate bottom track) in section II. All tracks in section II between
 the penultimate bottom track and the penultimate upper track are then
 filled while the tape 1 is alternatingly moved backward and forward. When
 the track immediately below the penultimate upper track in section II is
 filled, the read/write head 2 is moved downwardly to enter data into the
 bottommost track in section II, and at the end of that track in section
 II, the drive moves the tape 1 so that a new section, arbitrarily
 designated as section III, is filled, beginning with the bottommost track
 therein. Section III is filled with the tape 1 being alternatingly moved
 backward and forward, until all tracks in section III are filled with
 data, whereupon the drive moves the tape 1 so that the uppermost track in
 section II is filled, and then moves the tape again so that the uppermost
 tracks in each of sections I and section IV are filled. Upon reaching the
 end of the uppermost track in section IV, the read/write head 2 is
 vertically positioned downwardly to the track in section IV which is two
 tracks away from the bottommost track in section IV. The drive
 alternatingly moves the magnetic tape 1 back and forth until the
 penultimate upper track in section IV is filled, whereupon the read/write
 head 2 is moved downwardly to the penultimate bottom track in section IV
 (which is immediately above the bottommost track) in section IV, and that
 track and the bottommost track in section IV are filled.
 The tape is then moved to fill the bottommost track in section I, at which
 point the end of program EOP is reached.
 The respective longitudinal lengths of the sections can be set by
 programming a specific number of bits per row in the bit output program so
 that when that number of bits is reached, an automatic tape transport
 direction reversal takes place. The respective longitudinal lengths of the
 sections need not be equal, but the maximum advantage of the inventive
 method will be achieved if all of the longitudinal lengths of the
 respective sections are equal.
 Of course, the method can be implemented with any number of sections, with
 a minimum of two sections, one on each side of the COT region, i.e., one
 region completely filling the region between the COT region and the BOT
 region, and another region completely filling the region between the COT
 region and the EOT region.
 Vertical movement of the read/write head in a controlled manner can be
 accomplished by any conventional head stepping mechanism and control
 apparatus therefor.
 More than four sections can be employed in the inventive method, however,
 it is apparent that the gain in access time, which results from smaller
 data sections which must be searched or traversed in order to gain access
 to predetermined data, is offset to a certain extent because the writing
 time will be slightly increased by the increased number of tape direction
 reversals and vertical head movements.
 It is also possible to control the splitting of the sections by means of
 additional holes punched in the tape 1, such as a section split hole SS1
 between sections III and II, and a section split hole SS2 between sections
 I and IV. The holes SS1 and SS2 will be recognized by the optical system
 of the drive, and will then control the reversal of the tape transport
 direction when encountered. Moreover, in order to allow completely
 unrestricted write sequencing, a track ID has to be added at the start of
 each of the new sections. These track IDs can be written as part of the
 bit output program at the beginning of each section.
 As noted above, dependent on the longitudinal length of the COT region, and
 the number of sections. In the embodiment of the inventive method wherein
 only two data recording sections are employed, one between the COT region
 and the BOT region and the other between the COT region and the EOT
 region, all tracks will be filled from BOT to EOT or vice versa, except
 for the first track will start at the COT region and the last track which
 will end at the COT region. There is, as noted above, an interruption in
 the data writing as the COT region is traversed. For the embodiment of
 FIG. 2 wherein the COT region has a longitudinal length of 196 inches,
 each traversal of the COT region requires 1.67 seconds at a conventional
 tape transport speed and each track is traversed in a total time of 150
 seconds. This would result in an increased time of 1.11% to fill the
 entire tape with data, compared to a conventional writing procedure
 wherein writing proceeds uninterruptedly from BOT to EOT. In the
 embodiment of FIG. 3, wherein the COT region occupies only 24 inches, the
 time to traverse this region is reduced to 0.23 seconds, and the increased
 time is then only 0.15%.
 In the embodiment of the method illustrated in FIG. 4, wherein data are
 written in four sections on the tape 1, it is estimated that the time to
 fill the entire tape (i.e., all sections) with data will increase by about
 2.0%, compared to a conventional tape and a conventional writing method.
 This assumes, however, that the data are written on the tape 1 in a
 continuous streaming procedure starting with a blank tape and ending with
 a completely filled tape. It is more likely that only portions of the tape
 will be written at a time, perhaps only one section at a time, in which
 case the increased writing time will be considerably reduced.
 The above exemplary embodiments have been described in the context of holes
 being used for the various markers. It is known in the art to employ other
 types of markers instead, such as reflective markers or magnetic markers.
 These add to the complexity of the drive and therefore markers in the form
 of holes are preferred, however, the inventive method and tape can employ
 any suitable type of marking arrangement.
 Although other modifications and changes may be suggested by those skilled
 in the art, it is the intention of the inventor to embody within the
 patent warranted hereon all changes and modifications as reasonably and
 properly come within the scope of his contribution to the art.