Making computers ‘personal’ was as much a problem of user enrolment and education as it was of hardware development. Getting mass-participation computing to work required technology firms to engage with the social organization of user groups. Accounts of this process have tended, however, to ignore the very first “personal computers” to come to market, a series of handheld programmable calculators launched in the mid-1970s. The Whipple Museum’s Hookham Collection of pocket electronic calculators contains both devices and ephemera produced by firms such as Hewlett-Packard that became popular for their capacity to store and load programs that could be traded between users. This soon fed into the organization of collective hobbyist newsletters and groups that exchanged programs and advice, allowing for thousands of professionals to become programmers. In this chapter, I explore the development of infrastructure that characterized the first amateur programming collectives and the moral, monetary, and material economies involved, in an attempt to tackle one of the more intractable questions in the history of modern technology: how did computing become personal?