Abstract: Method and apparatus are disclosed for a data recording disk file having a head module with separate side by side read and write transducers for optimizing the switching of the head between reading information and writing information on the same track or cylinder. A function generator defines at least one control function for a servo control signal to drive an actuator to move the head module the approximate distance between the side by side write and read transducers, optimized to minimize the time between write and read, and optimized to move the head module the approximate distance between the side by side read and write transducers at the timing best suited to minimize the write transition time.

Abstract: Digital data is stored on a DASD by generating a parity block for a specified block of data items and storing the parity block at a selected location on the DASD. The parity block includes a parity computation calculated by applying a parity routine to the corresponding data. The parity block also includes a parity code that indicates either (1) the size of the corresponding data block, or (2) the number of data items contributing to the parity computation. The parity block may be stored adjacent to the corresponding data, or at an independent location. Among other things, the invention provides significantly increased robustness against data loss, and improved flexibility and efficiency in storing data.

Abstract: A method and apparatus for the point plotting and rearrangement of graphical data from a coded source into a buffer for raster type display. The execution of a graphic order in a stored program controllable graphics terminal are represented by a line generating a sequence of X Y coordinate values, which values are to be plotted or displayed. The points are plotted into a work organized memory array in the form of topologically adjacent rectangular subarrays. These subarrays are then transformed into linear arrays. In order to conserve memory they directly replace the previous topologically adjacent subarrays in the memory. The linear arrays may then be accessed a word at a time and applied to the raster display.