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Pilot: A Software Engineering Case Study by Thomas R. Horsley and William C. Lynch July 10, 1979 ABSTBACT Pilot is an operating system implemented in the strongly typed language Mesa and produced in an environment containing a number of sophisticated software engineering and development tools. We report here on the strengths and deficiencies of these tools and techniques as observed in the Pilot project. We report on the ways that these tools have allowed a division of labor among several programming teams, and we examine the problems introduced within each different kind of development programming activity (ie. source editing, compiling, binding, integration, and testing). XEr{OX SYSTEMS DEVELOPMENT DEPARTMENT 3408 Hillview Ave / Palo Alto / California 94304 2 T. R. HORS[ EY A:-';l) W. C. LYt\CH Introduction The purpose of this paper is to describe our experiences in implementing an operating system called Pilot using a software engineering support system based on the strongly typed language Mesa [Geschke et of, 1977, Mitchell et 01, 1978], a distributed network of personal computers [Metcalfe et 01, 1976], and a filing and indexing system on that network designed to coordinate the activities of a score or more of programmers. In this paper we will present a broad overview of our experience with this project, briefly describing our successes and the next layer of problems and issues engendered by this approach. Most of these new problems will not be given a comprehensive discussion in this paper, as they are interesting and challenging enough to deserve separate treatment. lbat the Mesa system, coupled with our mode of usage, enabled us to solve the organi7C1tional and communication ploblems usually associated with a development team of a score of people. These facilities allowed us to give stable and non-interactive direction to the several sub-teams. We developed and used a technique of incremental integration which avoids the difficulties and schedule risk usually associated with system integration and testing. . lhe use of a Program Secretary, not unlike Harlan Mills' program librarian, proved to be quite valuable, particularly in dealing with situations where our tools had weaknesses. We showed the worth of the program librarian tool, which helped coordinate the substantial parallel activity we sustained; and we identified the need for some additional tools, particularly tools for scheduling consistent compilations and for controlling incremental integrations. We determined that these additional tools require an integrated data base wherein consistent and correct information about the system as a whole can be found. Background Pilot is a medium-size