Mainframe to Microcomputer Software Transportability
Authors: Seehafer J.A. 
Published: December 2007

SPE Member

Abstract
Transferring mainframe applications to microcomputers usually entails moving, recompiling, and relinking the source code to eventually build an executable version on the microcomputer. Recent technological advances in hardware and operating system software have eased the task of moving mainframe applications to microcomputers. However, certain transportability problems might still need special attention. For instance, code changes are frequently necessary to enable proper execution of the program on the target system. Care must be taken to ensure consistency between the mainframe and microcomputer versions so future maintenance can be handled easily. To assist the user, who may be exposed to both systems, program operation on the microcomputer should be much like program operation on the mainframe.
Most of Amoco's drilling software development and enhancement work is done on a mainframe. At this time, special attention is paid to producing "transportable" code. This facilitates later implementation of a mainframe application on a microcomputer and has proven beneficial in two ways. First, the initial move to the microcomputer requires few, if any, code changes. Second, technical enhancements to both mainframe and microcomputer versions can be handled without extensive software conversion.
This paper describes some of the problems encountered when moving petroleum industry Fortran applications from a mainframe to microcomputers. It provides details on how Amoco successfully addressed the transportability problem from both the user's and software developer's viewpoints. It also discusses experiences in implementing and maintaining technical applications in a mainframe/microcomputer environment.

Introduction
Computing plays an important role in Amoco's drilling research. Mainframe computers have been used to develop programs that model various aspects of the drilling process. These "Technical Drilling Applications," Table 1, provide a means whereby drilling technology is transferred from the research center to the field. These programs are available on mainframe computers to drilling engineers in Regional and District offices throughout the continental U.S. and Canada. Corporate computer centers in England, Trinidad, and Egypt also provide mainframe access to the Technical Drilling Applications.
During the late 70's and early 80's, Amoco employed a variety of minicomputers as tools for technology transfer. They were used in locations that did not have access to any of the corporate computing facilities. Hardware used in remote locations had to meet several requirements. It had to be reasonably portable, it had to function without special housing or power, it had to support Fortran, and it had to be capable of running the drilling applications in reasonable times. Advances in microcomputer technology during the early 80's enabled several micros to meet these requirements. This naturally led to their utilization for remote location computing. Microcomputers have gradually replaced minicomputers as remote location technology transfer tools.
Implementing and maintaining a series of application programs on both mainframe and microcomputers has necessitated the special consideration of another technical aspect of software development - Transportability.

Why Worry About Transportability
Research in the general area of drilling continually produces new technology.
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