|I||||||III US005619682A United States Patent (19) 11) Patent Number: 5,619,682 Mayer Et Al
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|I||||||III US005619682A United States Patent (19) 11) Patent Number: 5,619,682 Mayer et al. (45) Date of Patent: Apr. 8, 1997 54 EXECUTING NETWORK LAYERED Hartig et al., "Operating System(s) on Top of Persistent COMMUNICATIONS OF A FIRST SYSTEM Object Systems-The Birlix Approach”, Jan. 1992, pp. ON A SECOND SYSTEM USINGA COMMUNICATION BRIDGE TRANSPARENT 790-799, IEEE. TO THE DIFFERENT COMMUNICATION LAYERS Primary Examiner-Thomas C. Lee 75 Inventors: Bruce D. Mayer, Arlington; Martin Assistant Examiner-Sang Hui Kim Berkowitz, Newton; Sudershan K. Attorney, Agent, or Firm-Gary D. Clapp, Faith F. Driscoll; Sharma, Brookline, all of Mass. John S. Solakian 73) Assignee: Bull HN Information Systems Inc., Billerica, Mass. (57) ABSTRACT 21 Appl. No.: 127,925 A layered communications bridge mechanism connected 22 Filed: Sep. 28, 1993 between an upper communications layer of a first commu (51) int. Cl. ..................... G06F 3/00 nications layer mechanism executing in a user level process 52 U.S. Cl. ................... 395/500; 364/264.3; 364/2809; and a layered communication kernel process of a second - 364/280; 364/DIG. 1 system corresponding to the next lower layers of the first 58) Field of Search .................................... 395/500, 2.86, communications layer mechanism. The bridge includes an 395/700, 650, 882, 892 upper bridge mechanism operating to appear to the lowest (56 References Cited layer or the layers of the first communications layer mecha U.S. PATENT DOCUMENTS nism to be the next lower layer of the first layered commu nications mechanism and a lower bridge mechanism oper 4,727,480 2/1988 Albright et al.. 4,812,975 3/1989 Adachi et al. .......................... 395/500 ating to appear to the upper communications layer of the 5,136,709 8/1992 Shirakake et al... ... 395/700 second system kernel process to be the next higher layer of 5,179,666 1/1993 Rimmer et al...... ... 395/882 the communications layers of the second system and the 5,210,832 5/1993 Maier et al. ........ ... 395/375 5,265,252 11/1993 Rawson, III et al. ... 395/700 upper and lower bridge mechanisms operate to map between 5,416,917 5/1995 Adair et al. ............................. 395/500 the operations of the lower layer of the first communications FOREIGN PATENT DOCUMENTS layer mechanism and the upper layer of the layered com munications layers of the second system. The upper bridge 0.1244935 8/1991 Japan. mechanism executes in the second system user process and OTHER PUBLICATIONS the lower communications layer bridge mechanism executes "Bull repond a ses utilisateurs', 01 Informatique, Jun. 12, in an emulator executive level. 1992. “HP 3000 Emulation on HP Precision Architecture Com puters', by Arndt B. Bergh, et al., Dec., 1987, Hewlett-Packard Journal, pp. 87-89. 7 Claims, 6 Drawing Sheets FOSL U.S. Patent Apr. 8, 1997 Sheet 1 of 6 5,619,682 "OIHI 0!WELSAS1SHI-H ||]-z?TEMAET?72LavsBEST! 91 U.S. Patent Apr. 8, 1997 Sheet 4 of 6 5,619,682 100 SEMAPHORE FIG. 4 5,619,682 1. 2 EXECUTING NETWORK LAYERED the specific operations desired by the user to perform the COMMUNICATIONS OF A FRST SYSTEM user's work, such as word processing, spread sheets, and so ON A SECONO SYSTEM USING A forth. The hardware is comprised of the central processing COMMUNICATION BRIDGE TRANSPARENT unit, the memory and the input/output devices, such as TO THE DEFERENT COMMUNICATION 5 displays, printers, disk drives and communications devices, LAYERS which actually perform the required operations at the detailed level. CROSS REFERENCES TO RELATED The operating system is functionally located "between' APPLICATIONS the user programs and the hardware and is comprised of a set The present patent application is related to: 10 of programs and routines that control the overall operations of the system and a set of routines that control the detailed U.S. patent application Ser. No. 08/128,456, filed Sep. 28, operations of the hardware as necessary to manage and 1993, for Executing Programs Of A First System. On A execute the operations directed by the applications pro Second System by Richard S. Bianchi et al. pending; grams. In this regard, the operating system is frequently U.S. patent application Ser. No. 08/127,397, filed Sep. 28, 15 comprised of two functional layers. One layer, frequently 1993, for Emulation of Disk Drivers of AOf A First System referred to, for example, as the "executive' level, interfaces On A Second System by Richard S. Bianchi et al. now U.S. with the applications programs and is comprised of a set of Pat. No. 5,373,984; and programs and routines and data structures which create U.S. patent application Ser. No. 08/128,391, filed Sep. 28, operations referred to as "processes' or “tasks" which 1993, for Emulation Of The Memory Functions Of A First 20 execute, at a high level, the operations required by the user System On A Second System by Marek Grynberg et al. programs. The "executive' level also includes a set of which issued as U.S. Pat. No. 5,515,525. programs, routines and data structures that are used to manage and execute the operations required by the applica FIELD OF THE INVENTION tion programs and which generate requests to the lower level 25 The present invention relates to a method and apparatus of the operation system. for executing programs of a first system on a second system The lower level of the operating system, frequently and, more particularly, to a method and apparatus for emu referred to as the "kernel', interfaces with the hardware lating a first operating system and hardware platform on a elements of the system and is comprised of a set of routines, second operating system and hardware platform. frequently referred to as "drivers' or "servers', for detailed 30 control of the operations of the system hardware. The kernel BACKGROUND OF THE INVENTION routines receive the requests for operations from the execu tive level and in turn direct the detailed operations of the A recurring problem in computer systems is that of system hardware elements. executing, or running, programs written for a first computer The basic problem in moving an application program system having a first hardware platform, that is, processor, 35 from a first system to a second system arises because, memory and input/output devices, on a second computer although the system is comprised of separate functional system having a second and different hardware platform. layers, the characteristics of each functional layer and of the The problem is compounded when the second computer functions and operations performed by each functional layer system, as is frequently the case, uses a second operating are affected by the characteristics and functions of at least system which may be substantially different from the oper the next lower layer. That is, the application programs are ating system of the first system. written to take maximum advantage of the characteristics This problem usually occurs when a user or a manufac and features of the executive level of the operating system. turer of computer systems is attempting to move application The executive level of the operating system, in turn, is programs from a first system to a second system to upgrade 45 designed to take maximum advantage of the characteristics or update the computer system while, at the same time, and features of the kernel level of the operating system while preserving the user's investment in application programs the kernel level is similarly designed not only to carry out and data created through the application programs. This the operations and functions required by the executive level situation may arise, for example, when moving application but is influenced by the characteristics and functional fea programs from one proprietary system, that is, a system 50 tures of the system hardware devices. having an operating system and hardware platform which is It is apparent, therefore, that the characteristics of a particular to one manufacturer, to another proprietary system system as viewed by an application program are influenced OR when moving application programs from a proprietary by features and functions of the system from the executive system to a "commodity' system, that is, a system having a level of the operating system down to the actual hardware hardware platform and operating system which is used by 55 elements of the system. As a consequence, and even though many manufacturers. systems are designed to maintain the maximum clear sepa The problems arising from moving application programs ration and independence between functional layers, a func from a first system to a second system arise from the tional layer created for one system, such as an application fundamental functional structure of the systems and from the program or an operating system, will rarely be compatible interactions and interrelationships of the functional elements with or function with a functional layer from another system. of the systems. The two primary approaches taken in the prior art for Computer systems are constructed as layered levels of moving an application program from a first system to a functionality wherein the three principal layers in any sys second system are the recompilation of the application tem are, from top to bottom, the user programs, the operating program to run on the second system directly and the system and the hardware "platform'. The user programs 65 emulation of the first system on the second system so that the provide the primary interface to the users and provide the application program can be run unchanged on the second functions and operations to control the system in performing system.