Abstract: Rate 8/9, constrained codes having run length limitation parameters (0, 4/4) and (0, 3/6) are provided for any partial response (PR) signalling system employing maximum likelihood (ML) detection.

Abstract: A transimpedance amplifier for biasing and amplifying the signals produced by a magnetoresistive element is provided. Electrically, the resistance of the element is disposed as degenerative feedback in the emitter circuit of a differential pair comprising the input stage of the amplifier. Bias current for the element is supplied by the same current source that supplies current to the differential pair. DC feedback to the input stage balances current flow in both paths of the differential input stage to correct for DC offset arising in the output from variations transistor characteristics and the steady-state value of the magnetoresistive element. The amplified signal, representing .DELTA.R.sub.h /R.sub.h, is sensed as a current through the magnetoresistive element, where .DELTA.R.sub.h is the change in steady-state resistance, R.sub.h, of the element.

Abstract: Disclosed is a method for recording a record that emulates a first recording format, which includes a track reference point, such as an index field, used for determining a position of a record on a track according to the first recording format, on a moving storage device operating according to a second recording format which also includes a track reference point. The invention comprises the steps, responsive to location information generated according to the first recording formats, of:(1) determining an original angular position of a record according to the first recording format;(2) calculating in response to the original angular position and a parameter a preferred angular position for the record according to the second recording format;(3) determining an actual angular position of the record recorded according to the second recording format; and(4) recording an extension of the record to compensate for the difference between the preferred angular position and the actual angular position.

Abstract: A magnetic recording disk includes a silicon substrate which is extremely flat and essentially asperity-free. A nonmagnetic underlayer is deposited on the silicon to enhance the magnetic performance of the magnetic layer which is deposited on the underlayer. A protective nonmagnetic overlayer is deposited on the magnetic layer.

Abstract: A programming method and structure for operating a computing system to restart a total subsystem or a subset of that subsystem to an operable state following a total interruptions (system failure or termination, either normal or abnormal). The subsystem isolates inoperable resources while permitting the others to resume by independently maintaining in a first structure recording the completion state of a resource manager's recovery responsibility with respect to each interrupted work unit and in a second structure the operational states and recovery log interest scopes of each resource manager. The completion state can be influenced by the starting or not of a resource manager, and if restarted, the presence or absence of a resource subset required to accomplish the work unit recovery.

Abstract: A method of editing at a processor text formed by lines of characters received by the processor from a remote source whereby communication between the processor and the remote source is minimized. The method steps at the text processor include (a) generating a respective checking number corresponding to each line of characters received from the source; (b) modifying the received text to form a body of lines by selective addition, modification, or deletion of lines and characters; (c) generating a checking number for each line of modified text in the manner of step (a); and (d) associatively comparing the checking numbers of consecutive counterpart lines of the modified text with those of the received text and transmitting back to the remote source the entire text of only those lines which have been modified as denoted by said lines having checking numbers mismatching those of the received text.

Abstract: A method of etching silicon with a laser at a very fast rate of the order of 45 microns/second includes the steps of providing an atmosphere of sulfur hexafluoride about the silicon and directing a continuous laser beam having a wavelength of about 0.6 or less microns at said silicon.

Abstract: A storage device, such as a direct access storage device, is partitioned into a plurality of partitioned devices having different access and storage characteristics matched to the required perforamnce. Data may be stored on that partitioned device which most nearly meets the storage characteristics of the data, where the access and storage characteristics of data are related to its volume and frequency of access.

Abstract: The invention relates to a composite magnetic disk for magnetic recording, which consists of an annular core of polymeric material to which is bonded at least one disk of reaction-bonded silicon carbide with a magnetic recording layer on its outer surface. After its processing, the SiSiC disk surface shows optimum planarity and smoothness so that it can be used as a magnetic disk substrate. Furthermore, the material has a low density and an extremely high specific modulus of elasticity so that numbers of revolution higher than obtainable with formerly known AlMg5 disk substrates can be reached.

Abstract: A method of and structure for optical recording by energy-induced homogenization or fractionation is disclosed. When the method involves fractionation, a film is provided that contains a homogeneous mixture of a matrix material and an incident energy absorbing material. A spot on the film is treated with sufficient energy in the form of electric fields, radiation or heat, or combinations thereof to effect fractionation and/or homogenization of the film which will undergo further physical state transition only under treatment with additional energy. In a preferred embodiment, the fractionation is effected by laser radiation. The laser irradiated spot becomes inhomogeneous and can be detected by the resulting changes in its optical properties. When the method involves homogenization, a film is provided that contains a inhomogeneous mixture. The energy treated spot in this case becomes homogeneous without undergoing a phase transition between the amorphous and crystalline phases.

Abstract: An apparatus and method are described for incorporating doping material into a single silicon crystal by an improved float zone (FZ) crystal growth method. A solid fused silica doping rod is inserted into a floating zone of molten silicon in a controlled manner, preferably via a generally radial hole through a radio-frequency induction coil. Oxygen doping, in a concentration of 1-25 ppm, is achieved by using a fused silica doping rod. N- or p-type dopants may be contained in the silica rod as impurities to provide n- or p-type doping concurrently with the oxygen doping.

Abstract: A magnetic head slider consisting of a mixed ceramic made of aluminum oxide/titanium carbide has on its sliding side adjacent a magnetic record carrier a thin layer from which the titanium carbide component has been removed. The titanium carbide component preferably is removed by preferential reactive ion etching in a CF.sub.4 plasma. The magnetic head slider with its sliding surface thus modified exhibits greatly improved sliding properties compared with sliders of the same material having a non-modified sliding surface.

Abstract: A recording channel for a disk file including analog circuits implemented in integrated circuits whose frequency dependent parameters are controllable in response to the value of a control signal supplied to the circuit, as determined by a digital signal. In the preferred embodiment, the control signal to each analog circuit is from a digital to analog converter that is supplied with a digital signal from a register that is addressable and settable from a programmed microcontroller. Certain registers are able to be incremented or decremented by separate clock pulses and function as counters that are controlled by a signal in a feedback path separate from the microcontroller. Components external to the integrated circuits are, therefore, avoided while still maintaining the ability to adjust the analog read circuits to be responsive to data rates of different frequencies.

Abstract: A frequency multiplexed optical spatial filter is based upon a thin film of a photochemical hole burning material. The filter stores a plurality of images in the photochemical hole burning medium. The images are formed at different optical frequencies and coexist in the same volume of the storage medium. Individual images are accessed by changing the frequency of the illuminating radiation.

Abstract: A method is disclosed for controlling the concentration of airborne particulate contaminants in a clean room environment. Air under pressure is continually recirculated through the environment and filtered as it is circulating. Mixing of the filtered air is enhanced by imparting turbulence thereto sufficient to render the filtered air substantially homogenous. The particle count of the filtered air is sensed within the environment and the volume of air that is recirculated is controlled according to the sensed particle count to thereby maintain the particle count substantially at a preselectable concentration.

Abstract: A two-level multibyte error correcting system is disclosed for correcting up to t.sub.1 one-byte errors in a codeword in response to processing 2t.sub.1 non-zero syndrome bytes at the first level and up to t.sub.2 one-byte errors in a codeword in response to processing 2t.sub.2 non-zero syndromes bytes at the second level when processing said 2t.sub.1 syndrome bytes at said first level does not produce an all zero pattern for said 2t.sub.2 syndrome bytes. A relatively long block of data may be divided into subblocks, each of which may contain up to t.sub.1 -x one-byte errors that are correctable at the first level by processing 2t.sub.1 non-zero syndrome bytes where one identifiable subblock of the word may contain up to t.sub.1 +x one-byte errors which are correctable by processing said 2t.sub.2 non-zero syndrome bytes where 0.ltoreq.x.ltoreq.(t.sub.2 -t.sub.1).

Abstract: A syndrome processing unit for a multibyte error correcting system is disclosed in which logical circuitry for performing product operation on selected pairs of 8-bit syndrome bytes and exclusive-OR operations on selected results of the product operations are selectively combined to define usable cofactors that correspond to coefficients of an error locator polynomial corresponding to a selected codeword if the codeword contains less than the maximum number of errors for which the system has been designed.

Abstract: A method for improving the durability, surface finish, and magnetic properties of a magnetic recording disk, the recording disk having a magnetic coating material with load bearing particles therein, by applying thereto a deformational force which exceeds the elastic limit of the coating material.

Abstract: A composite structure for magnetic recording includes a core member of polymeric material to which is bonded at least one silicon disk having a magnetic recording material on its outer surface. The silicon disk surface provides optimal flatness and smoothness characteristics for a magnetic recording substrate, while the polymeric core member provides strength to the structure.