Abstract: The system and method of this invention authorizes a process running at a client data processing system to have access to a service at a server data processing system. The data processing systems are connected by a communication link in a distributed processing environment. A set of credentials for the process are created at the server in response to a message from the client requesting a service. The server returns a credentials id identifying the created set of credentials to the client process. The client uses this returned id in subsequent requests and is authorized access as controlled by the set of credentials identified by the returned id in the subsequent request. The server can deny access to the service by the process if the id returned in a subsequent request is determined by the server not to identify the set of credentials. The server denies the access if the server requires an authentication of the process.

Abstract: A method of, and apparatus for, running several applications concurrently on a processing system. Virtual terminals are created for running the applications. However, the virtual terminals perform as though the processing system were a single terminal system. In this way, any application written for a single terminal system can run in this multiple virtual terminal environment. For interaction with one of the several applications running on this system, the real physical resources of the system are reallocated to the virtual terminal running the selected application.

Abstract: A tool for a display system comprises means for superimposing a box on a portion of a buffer of data visible on a display; the box being representative of the size and location of the visible portion with respect to the whole of the buffer. For example, a box of an appropriate size can be superimposed on a portion of a buffer of data displayed in a window at an appropriate location in the window to allow the two-dimensional extent of the visible portion of the buffer with respect to the rest of the buffer of data to be represented in an easily understood manner. The invention finds particular application as part of a scroll tool. By the provision of means for interacting with the scroll box the user is provided with a user-friendly manner of scrolling around a document in a plurality of directions. This scroll tool is much more convenient to use than conventional scroll bars and does not take up unnecessary screen real estate.

Abstract: The system and method of this invention controls how client data processing systems in a distributed networking environment can efficiently extend files and write into regions of the files previously unoccupied by data. The server data processing system manages the distributed allocation of new file blocks by sending nascent zeros in addition to real bytes that have been requested by the client data processing system. Nascent zeros are logically zero bytes that have never been stored to or written to, and may be outside the current extent of the file. The server determines whether or not this additional range of nascent zeros will be sent to a client depending upon the amount of physical storage available at the server, and whether or not other client data processing systems require access to this range of blocks. Likewise, the client data processing system has the option of writing to this additional range of nascent zeros.

Abstract: A communication protocol for direct communications between operating system kernels of a plurality of processors in a clustered-type, shared virtual memory, multi-processor data processing system is disclosed. Each processor unit includes a intermachine communications software system ("IMCS") which may-be used by a trusted kernel of the operating system of the processor to communicate with a service in another processor, either directly or through an intermediate processor. Communications are initiated when a user prepares a message in accordance with pre-programmed instructions from the IMCS in a standard format. Once the message is prepared, the user calls IMCS which selects a route for the transmission of the message over a serial communications link to the receiving processor using a "request to send immediate" serial link level protocol. The message is initially directed to a common buffer pool.

Abstract: A method for minimizing I/O mechanical assess operations on secondary storage devices in a data processing system having a plurality of processor units interconnected in a cluster configuration to permit each processor unit to request and obtain data that is resident only on a secondary storage device of one processor unit. The method involves the steps of maintaining at each processor unit information about each copy of data that has been sent from the unit to another unit to permit a second request to the unit to be serviced by transferring a copy of the data from the main memory which is storing the data to the requesting unit rather than servicing the request with a relatively slow I/O accessing operation to a secondary storage device.

Abstract: A system for maintaining the reliability of shared data structures, such as message queues, in a multi-processor data processing system is disclosed. The system includes a plurality of virtual memory-type processor units in which the processors share virtual memory and can access each one of a plurality of virtual memory segments by the same virtual memory address. The system assures the reliability of system-wide shared data structures in the event of a failure of one of the processors by maintaining at least two copies of each data structure and by maintaining two copies of a table used in locating such data structures. The system updates copies of such shared data structures that are stored in at least two different processing units with the results of a specified data processing transaction, which may have affected the information in such data structures, in a manner to insure that either identical updates occur or no update occurs.

Abstract: The system and method of this invention simulates the flow of control of an application program targeted for a specific instruction set of a specific processor by utilizing a simulator running on a second processing system having a second processor with a different instruction set. The simulator reduces the number of translated instructions needed to simulate the flow of control of the first processor instructions when translating the address of the next executable instruction resulting from a dynamic transfer of control, i.e., resulting from a return instruction. The simulator compares the address that is loaded at run time by the return instruction with the return address previously executed by that instruction. If the last return address matches, the location of the return is the same. If the last return does not match, a translate look-aside buffer is used to determine the address.

Abstract: The system and method of this invention automatically routes a connection between data processing systems in different network domains. As an example, an application running on a data processing system utilizing a network domain such as TCP (Transmission Control Protocol), can automatically make a connection to another data processing system utilizing a different network domain such as SNA (Systems Network Architecture). The connection is automatically performed in the layer containing the communication end point objects. In a preferred embodiment, the connection is automatically performed in the socket layer of the AIX operating system, or in the socket layer of other operating systems based upon the Berkeley version of the UNIX operating system.

Abstract: The system and method of this invention allows a simulated processor to receive an interrupt request from I/O devices. A simulated interrupt controller routine determines whether to post an interrupt to the simulated CPU. The simulated interrupt controller routine posts an interrupt to the simulated CPU by updating one byte, which is owned by the simulated interrupt controller, of a two byte halfword. The other byte is owned by the simulated CPU and is updated by the simulated CPU when its internal interrupt enabled state changes. Each byte of the two byte halfword is updated independently, but is loaded by the simulated CPU with only one instruction to determine if an interrupt should be acknowledged.The simulated CPU minimizes the overhead of polling for an interrupt by performing a graph analysis of the instruction flow of control to determine the locations to poll for interrupts.

Abstract: The system and method of this invention maintains the latest file attributes such as file size, modify time, and access time, at the server data processing system in a distributed data processing system. The server data processing system combines information requested from the client data processing system that has permission to write to the file with information periodically received from other client data processing systems that may be extending the same file by mapping the file into their own virtual address space. In this way, the server can maintain the latest file size attribute even when some clients are extending the file through system calls and other clients are extending the file through mapped access. To maintain a latest modify time and access time, the server keeps a modify count and access count.

Abstract: A method of, and apparatus for, running several applications concurrently on a processing system. Virtual terminals are created for running the applications. However, the virtual terminals perform as though the processing system were a single terminal system. In this way, any application written for a single terminal system can run in this multiple virtual terminal environment. For interaction with one of the several applications running on this system, the real physical resources of the system are reallocated to the virtual terminal running the selected application.

Abstract: The system and method of this invention controls the presentation of a text document from a processing system to a printer for printing rotated and non-rotated text within the same document. The portion of text that is to be printed sideways is designated by inserting a marker at the beginning and end of the portion of the text selected for rotation. The data stream between the markers representing the selected portion of text is stored in a buffer in the processing system in one sequence, and accessed from the buffer in a different sequence. The printer prints the data stream before the marker with an internal font having normal characters. When the first marker in the data stream is sensed, the printer is sent a control to change fonts. The printer prints the data stream in a different sequence after the first marker with an internal font having either left or right rotated characters.

Abstract: A data processing system gives an application running on the operating system direct access to the output display. The system is operable in two modes. In the first mode, if the application displays text to the output display, the output data must go through every layer of the processing system before it reaches the output display. In the second mode, the application can output data directly to the output display without going through the many layers of the processing system. In this second mode, a buffer is defined by the application. Input data from the input devices are stored in this buffer. The application accesses the buffer for direct output to the display.

Abstract: The system and method of this invention processes a data stream based on the structure of a font file which can be varied by a user or application of the processing system. The font file not only contains the pel patterns for a range of graphical symbols, but it also contains the rules for interpreting a data stream having a particular syntax. The rules for interpreting a data stream are referred to as the processing model for the data stream. The structure of the font file contains an index array to the range of graphical symbols. Each byte in the data stream is used to generate an index into the index array. In each element of the index array there is a value and control bits. The control bits indicate whether the value is an offset to a graphical symbol or whether the value is a modifier. If the value is a modifier, it is used to increment the next sequential data byte in the data stream through the range of graphical symbols.

Abstract: Two polygon fill algorithms are presented for filling polygons on a graphics display. The first polygon fill algorithm fills polygons that are strictly convex. The second polygon fill algorithm fills a larger class of polygons than the first polygon fill algorithm which includes polygons being concave in the x direction, and polygons having crossing lines. The first polygon fill algorithm tests the polygon for strict convexity by testing for a consistent turning direction, and by testing for once around in the y direction. The first polygon fill algorithm then stores the maximum and minimum value of the pel selected by the Bresenham algorithm for each scan line of the polygon. The fill line is drawn from the pel having the minimum value to the pel having the maximum value for each scan line of the polygon. The second polygon fill algorithm tests the polygon to ensure that it can be filled with one unique fill line for each scan line of the polygon.

Abstract: A terminal communications circuit that provides communication through a bus interface circuit to a network bus in accordance with the predetermined communications procedure, the terminal communications circuit including a communications interchange circuit that exchanges protocol signals with the bus interface circuit in response to commands received from a signal state controller that is resident in the terminal. The communications interchange circuit further provides communications state change information to the signal state controller to indicate the contents of the protocol signals from the bus information circuit. The signal state controller executes one of a plurality of program states to control communications over the network bus in accordance with predetermined communications procedure by providing commands to the communications interchange circuit in acordance with the program state that the signal state controller is currently executing.

Abstract: The system and method of this invention simulates the flow of control of an application program targeted for a specific instruction set of a specific processor by utilizing a simulator running on a second processing system having a second processor with a different instruction set. The simulator reduces the number of translated instructions needed to simulate the flow of control of the first processor instructions by performing a graph analysis on the application's instruction flow of control to determine which condition codes of each instruction are not needed for a subsequent instruction. Fewer translated instructions are needed if the condition codes for an instruction are not set or used subsequently.

Abstract: In a distributed environment several data processing systems are interconnected across a network system. A distributed services program installed on the systems in the network allows the processors to access data files distributed across the various nodes of the network without regard to the location of the data file in the network. The processing system accessing file, referred to as the client processing system, utilizes a client cache within its operating system to store the data file. Utilizing the client cache minimizes the number of reads and writes that must go over the network to the server processing system where the file physically resides. The system and method of this invention prevents a process in the client processing system from accessing data in the client cache that has been modified at another node in the network. The blocks of data in the client cache are tested for validity in the client processing system by using modification times as measured by the server processing system.

Abstract: The system and method provides a user interface tool for simultaneously selecting a menu item and a value, from a range of values, for the menu item. The user interface tool is referred to as a valuator menu, since it allows both the selection of a value from a range of values, and the selection of a menu item from a menu list. As a user moves a cursor over a menu of selectable items on a screen display, the item underneath the cursor is highlighted. In addition, as the user moves the cursor within the highlighted menu item, a value relative to the position of the cursor within that menu item is displayed. This valuator value is dynamically updated as the cursor position changes within the menu item. When the user performs an input selection, i.e. through a mouse button or a keyboard interaction, both the selected menu item and the value, relative to the cursor position, are simultaneously returned to the application program running on the data processing system.