What Makes the History of Software Hard
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What Makes the History of Software Hard Michael S. Mahoney Princeton University History of commitments constrains choice. Narrow incentives and opportunities motivate choice. —Rob Kling and Walt Scacchi1 We never have a clean slate. Whatever new we do must make it possible for people to make a transition from old tools and ideas to new. —Bjarne Stroustrup2 Creating software for work in the world has meant translating into computational models the knowledge and practices of the people who have been doing that work without computers. What people know and do reflects their particular historical experience, which also shapes decisions about what can be automated and how. Software thus involves many histories and a variety of sources to be read in new ways. This article originally appeared in L. Bo¨szo¨rmenyi, most current, is in that sense ‘‘legacy’’ soft- ed., MEDICHI 2007—Methodic and Didactic ware. That is what makes the history of Challenges of the History of Informatics, software hard, and it is why the history of Austrian Computer Society (OCG), Klagenfurt, software matters to the current practitioner. Austria, 178 pp. The Austrian Computer Society (OCG) has kindly granted permission for an edited Decentering the machine version to be published by the Annals.3 Until recently, the history of computing has focused largely on the machines them- The history of software is the history of how selves, tracing the path by which the electronic various communities of practitioners have put digital computer emerged from a long history their portion of the world into the computer. of efforts to mechanize calculation and then That has meant translating their experience evolved into a variety of increasingly complex and understanding of the world into compu- forms in response to the possibilities opened tational models, which in turn has meant by the transistor, the integrated circuit, and creating new ways of thinking about the world magnetic and optical media of ever greater computationally and devising new tools for capacity. This focus has led to a familiar expressing that thinking in the form of narrative (see Figure 1), which begins with working programs. It has also meant deciding, the abacus and then follows a by now familiar in each realm of practice, which aspects of sequence of devices—mechanical and electro- experience can be computed and which mechanical, analog and digital—all converg- cannot, and establishing a balance between ing on ENIAC, or more broadly on the several them. Thus, the models and tools that consti- electronic devices of a similar nature con- tute software reflect the histories of the ceived and built at the time. From ENIAC the communities that created them and cannot story moves to the EDVAC design and to its be understood without knowledge of those early realizations.4 The mainframe era then histories, which extend beyond computers begins, followed by the short reign of the and computing to encompass the full range minicomputer and then by the current age of of human activities. All software, even the the microcomputer in ever more powerful 8 IEEE Annals of the History of Computing Published by the IEEE Computer Society 1058-6180/08/$25.00 G 2008 IEEE form. The sequence is commonly treated as a natural evolution of forms. As each new generation appears, the old disappears from the story, as if mainframes went the way of the dinosaur when minicomputers appeared, and they in turn followed the mainframe into obsolescence as the microcomputer opened a new era of personal computing. It would be hard to know from most histories of this sort that IBM still derives a major share of its income from mainframe computers, especially as accounts of the Internet focus on the PC clients to the exclusion of the mainframe servers. Similarly, emphasis on the PC has hidden the ways in which with their growing power they have incorporated minicomputer architectures and Figure 1. The convergent account. systems and, with them, their mainframe legacy. Also lost from view with a focus on misleading in at least two ways. First, it makes the visible PC is embedded computing, which the application of the computer in a wide accounts for the vast majority of the micro- range of areas unproblematic. If people have processors at work today. been waiting for the computer to appear as the To the extent that the standard narrative desired solution to their problems, it is not covers software, the story follows the genera- surprising that they then make use of it when tions of machines, with an emphasis on systems software, beginning with program- it appears, or indeed that they know how to ming languages and touching—in most cases, make use of it. By the same token, it then just touching—on operating systems, at least becomes difficult to explain, for example, why up to the appearance of time-sharing. With a IBM would have hesitated to enter the com- nod toward Unix in the 1970s, the story moves puter market in the late 1940s, or why the quickly to personal computing software and National Institutes of Health had to launch a program to persuade biologists that computers the story of Microsoft, seldom probing deep 5 enough to reveal the roots of that software in could be of use to them. Second, the the earlier period. One may learn a bit about convergent account sets up a narrative of the beginnings of the data processing industry, revolutionary impact, in which the computer since it is synonymous with IBM, but there is is brought to bear on one area after another, in little if anything about the building of the first each case with radically transformative effect. large systems in business, industry, and gov- There is a lot of ‘‘revolution talk’’ in ernment. For this story, one must delve into computing. It dates back at least to 1962 with the specialist literature, much of it still the publication of Edmund C. Berkeley’s The dominated by ‘‘pioneer’’ accounts. The soft- Computer Revolution, in which the author made ware of the embedded systems underlying the the computer part of the ‘‘second industrial world’s technical, industrial, and financial revolution’’ and fretted over what was to infrastructure remains, of course, as invisible become of humans in an age of Giant Brains, to the historical record as do the devices on or Machines That Think (the title of his 1949 which it runs. book). One can hardly pick up a journal in Indeed, with respect to applications soft- computing today without encountering some ware, the standard narrative converges in sort of revolution in the making, usually another way. Just as it places all earlier proclaimed by someone with something to calculating devices on one or more lines sell. Critical readers recognize most of it as leading toward the electronic digital comput- hype based on future promise rather than er, as if they were somehow all headed in its present performance, and those with long direction, so too it pulls together the various memories recall the many revolutions that contexts in which the devices were built, as if have been canceled or postponed owing to they constituted a growing demand for the technical difficulties. invention of the computer and as if its Historians have grown wary of the notion appearance was a response to that demand. of revolutions, especially those that purport to That way of telling the story is historically erase the past or render it obsolete, as if July–September 2008 9 What Makes the History of Software Hard societies could start from scratch. There have been episodes in which societies changed The history of comput- radically over a relatively short period, and ‘‘revolution’’ seems an appropriate designa- ing, especially of soft- tion for the process, for example, the Industrial Revolution in England in the late 18th and ware, should strive to early 19th centuries. But even there one must be careful, because revolution talk tends to preserve human agency hide the continuities that tie the present to the past, or rather the continuities through which by structuring its the past informs the present. Nothing is in fact unprecedented, if only because we use prece- narratives around people dents to recognize, accommodate, and shape the new. In our personal encounters with new facing choices and situations, we turn to our memory for similar situations as a guide to how to respond. making decisions. History is our community memory, and it is as much embedded in our lives as our personal memories. Through language, customs, edu- In the impact model, ‘‘the computer’’ cation, and institutions, it informs the way we happens to people, who are put in the position think and the way we do things. It shapes our of responding to it. But computers do nothing expectations and our actions; it is built into without programs, and programs do not just our practices.6 As a senior colleague of mine happen by themselves. People design them for once remarked to a group of scientists, the their own purposes. Hence, the history of question is not whether one does history but computing, especially of software, should whether one does it well. For example, the strive to preserve human agency by structuring quest for a discipline of software engineering its narratives around people facing choices and began with a search for historical forebears, making decisions instead of around imperson- and the subsequent literature is filled with al forces pushing people in a predetermined appeals to the history of technology, some of direction. Both the choices and the decisions them well founded, others not.7 are constrained by the limits and possibilities of the state of the art at the time, and the state Histories of computing of the art embodies its history to that point.