Abstract: A magnetooptical disk recording device has a far-field detector for detecting radial position of a laser beam with respect to tracks on the disk. The far-field detector has a reference line dividing first and second photo detectors. The reference line is centered radially with respect to center lines of the tracks. The reference line is also center lengthwise to be tangentially center with respect to a tangential point on the track. The detector is adjustable both radially and tangentially. The tangential adjustment is based upon sensing two low reflective calibration marks on the disk that indicate centering the laser beam, hence the track tangent point, on the reference line. The calibration is based upon obtaining minimum noise in the detector output signal that signifies that the laser beam is centered on the length of the detector reference line. The calibration marks are in a mirror area disposed at one radial extremity of the disk.

Abstract: A parser for parsing computer programs in a compiler has parsing tables arranged as linear vectors. In a reduction portion of the parser, a production table and a lookahead set table have paired entries at identical address offsets such that a one-to-one relationship exists between each lookahead set in the lookahead set table and the representation of the lookahead set in the lookahead set table. In a read transition portion of the parser, an entrance symbol table has entries paired with transition state representations and each pair being at an identical address offset in the respective tables. For a reduction or read transition operation, the lookahead set table or the entrance symbol table is scanned to find the appropriate entry. Once the appropriate entry is found, the production table or the transition state table is addressed using the offset of the appropriate entry found during the scanning process.

Abstract: The disclosure relates to sequential performance of a cached data storage subsystem with a minimal control signal processing. Sequential access is first detected by monitoring and examining the quantity of data accessed per unit of data storage (track) across a set of contiguously addressable tracks. Since the occupancy of the data in the cache is usually time limited, this examination provides an indication of the rate of sequential processing for a data set, i.e., a data set is being processed usually in contiguously addressable data storage units of a data storage system. Based upon the examination of a group of the tracks in a cache, the amount of data to be promoted to the cache from a backing store in anticipation of future host processor references is optimized. A promotion factor is calculated by combining the access extents monitored in the individual data storage areas and is expressed in a number of tracks units to be promoted.

Abstract: In a magnetooptic record member the erasure direction for successive recording areas (sectors) are determined by the direction of magnetization of prior recording. A mark is placed in each sector for identifying its erasure direction. The mark is preferably a sequence of longer ones, of one-half wavelengths appearing in the recorded information-bearing signals. The erasure and recording directions are reversed such that in the recording direction in a successive recording area equal to the erasure direction of a proceeding area. This selection is based upon the current direction of a magnetic steering field.

Abstract: A track-seeking system for an optical disk using a velocity control loop with partially-digitized velocity measurement. A quadrature signal is generated based on summing the halves of a position error signal to give directionality to track-crossing counts. A so-called piggy-back construction, wherein a fine positioner is carried by a coarse positioner, is employed. Feed-forward controls are provided from the fine to the coarse positioner. At track-capture time, the dynamic range of the fine positioner is momentarily increased.

Abstract: An optical information-bearing-signal recorder employs thermally-induced recording of ablative, material movement, material phase change, magneto-optic or similar technologies. Synchronous noise in the recording is reduced by employing a heat-inducing energy pulse, coherent light for example, shaped to have an initial recording-initiating intensity amplitude followed by a recording-sustaining amplitude. The duration of the recording-initiating amplitude portion is constant for all lengths of signals being recorded. When a rotating optical disk is employed as a record-bearing medium, the recording-initiating and recording-sustaining amplitudes are increased with increasing radius of the recording on the disk.

Abstract: A method and a system for creating visual displays in a visual display device of data from an input data set. First, at least one of a plurality of stored sources of resource information is selected. Each of these sources is defined by and under the control of signals stored in a plurality of page definition files. These page definition files are stored separately from the input data set and the sources of resource information. Visual-presentation control signals are embedded into this input data set to generate an output data set. This selected resource information and the output data set are then stored in a local memory for enabling the desired visual displays.

Abstract: In a multiunit data processing system, such as a multicontrol unit peripheral data storage system, a least busy one of the units requests work to be done from a busier unit. The busier unit, a work sending unit, supplies work to the work requesting or least busy unit. Work thresholds in the respective units determine when work is to be requested or transferred. In a data storage environment, the transferred work consists of data transfers to be achieved usually asynchronously to connected host activities, such as data transfers between a backing and a front store in a data storage hierarchy.

Abstract: Copy production machine having a print mode for making copies under automatic control interruptible by a copy mode of making copies. In the print mode images to be copied are automatically supplied to a copy production portion. In the copy mode, a variety of image supplying techniques may be employed. Copy output means separate copies made from the two modes. In the print mode images are preferably precollated whereas in the copy, mode produced copies are collated. In a print mode plural image sources may be employed, such sources being activated ad seriatim.

Abstract: A peripheral device subsystem enables its peripheral devices to operate asynchronously with respect to attaches hosts through the use of managed buffers, new multiple data transfer modes, control and error recovery operations. In a preferred first or buffer mode of operation, all data of each record being transferred can be resident in a buffer before transfer to either a host or device. For a host to device write transfer, receipt of such a record by the buffer results in the subsystem signaling to the host a completion of a transfer to an addressed device even though the device has received none or only part of the data. In a second or tape write mode, recording data in a peripheral device, such as a tape recorder, completion of recording is not signaled until after the buffer has transferred the data to the recorder.

Abstract: A web transport, such as a reel-to-reel magnetic recorder, includes a web regulator between one reel and a transducing station. In a constant tension web transport, web regulator ensures a relatively constant length of web between the transducing station and the one reel. In a preferred form the regulator is a vacuum chamber having a narrow web receiving opening and a wider cavity such that as the web forms a bight in the chamber into said wider cavity, air flows past the web to regulate bight size in accordance with web tension tending to maintain a constant web length.

Abstract: Data processing workloads are balanced between a plurality of data processing units, such as control units of a peripheral system, based upon tallies of data processing delays. The workloads are arranged in work allocations, such as assignment of peripheral devices to a control unit; a separate delay tally is kept for each work allocation along with a summation of all delays in each control unit. When a tally threshold in any data processing unit is exceeded, load balance is examined. Upon a predetermined imbalance, a work allocation having a delay tally equal to a mean value of the different delay summations is transferred to a data processing unit having a lower delay summation.

Abstract: Direct access storage devices (DASD) are connected to a host via a cache. Each device can be independently addressed by any one of a plurality of addresses, also termed logical devices and exposures. Since operations between DASD and cache are combined for all of the independent logical devices, resetting operations related to one independent logical device can inadvertently interfere with operations of another independent logical device. To maintain data integrity, a programmed control accommodates logical device independence by using queues and control blocks relating to the DASD and logical devices, respectively.

Abstract: A data-processing system is connected to a peripheral system by a plurality of channel paths. These channel paths are named as members of path groups. Each path group has one or more channel paths. Within each path group, communications between the data-processing system and the peripheral system are multipathed among the paths in such path groups. Devices within the peripheral system are selectively assignable to access groups for exclusive use within one or more of such path groups; a given path group selectively provides communication paths for each device in an access group. Each access group includes one or more path groups. Temporary suspension and reassignment facilities are disclosed. Both devices and channel paths can be either in a grouped or ungrouped state. The assignment function to access groups is particularly useful in interleaved channel transfers for ensuring subsystem integrity.

Abstract: Resources shared by plural users supply a busy signal to a requesting user whenever any one of the users has a right of access to the resources. Ancillary data accompanies the busy signal identifying the user having the right of access. The requesting user may use the ancillary data to adjust its right of access by communication with the one user. The right of access may include a queue of access requests, each request having the ancillary data.

Abstract: A hierarchical communication system has multipaths for different levels of the heirarchy, each set of paths is assigned a criticalness to the successful operation of the system. Error rates for all of the paths are monitored. A threshold for defining an unusable data path is based upon the criticalness of the path to successful operation. That is, the more critical the path, the higher the error rate that will be sustained. A specific embodiment employs shift registers for indicating the error rate of the last predetermined number of usages of the given paths. A mass storage system employing the error-rate system is described.

Abstract: A disk accessing apparatus and method are disclosed for creating an axial spacing between two adjacent disks of a rotating disk stack. The accessing apparatus is mechanical and operates from one end of the stack of disks with one portion of the apparatus being movable axially with respect to the stack of disks and received within central apertures of the disks to contact at least one disk thereat and move the contacted disk axially away from an adjacent disk to create a transducer access opening therebetween. The apparatus can have a variety of configurations including utilization of axially displaceable disk engaging tumblers and/or pins axially movable through apertures or offsets at the central portion of the disks, fingers axially movable to engage disk tabs within the central apertures of the disks, and/or disk actuating, rotatable screw threaded shafts.

Abstract: Clock pulse plural cascade connected counters generate a plurality of patterns. Upon each clock pulse, the patterns in the plurality of counters are captured in a like plurality of registers. Each of the captured counts are then compared with one or more bit masks for determining identity. Detection of identity between any one of the plurality of masks with the selected ones of the registers results in the emission of a timing pulse. The initial counter states and the various mask values in the mask sets for the respective registers are program loaded. The apparatus can be computer monitored or can be programmed within a digital computer. Accordingly, the timing intervals are programmable by selecting diverse time-out lists.

Abstract: A single-gap transducer simultaneously senses recorded control or servo signals and record data signals. A magnetic medium used with this invention is preferably a single layer magnetic medium. The head gap length and pole-tip face length allow different portions of the pole pieces in a magnetic transducer to be utilized during the simultaneous read and record operations. The servo signals are preferably deep and hard recorded into the layer whereas the data signals are preferably pulse width limited and recorded adjacent the surface portion of the magnetic layer.

Abstract: A short duration pulse is recorded for each transition of a data bit stream. Such short duration pulses are AC bias recorded for enhancing recorder operations. The recording is preferably used with a buried control signal; the system enables simultaneous recording of data with reading or sensing the control signals. Specific equalization and detection techniques are disclosed. A DC restoring detector, operating synchronously to a detected bit stream, continually adapts its operation to readback signal amplitude variations. Because of high frequency aspects, the circuit elements can be mounted immediately adjacent a transducer or as close thereto as possible.