[5]: 5, 8–9, 11  Johnson died in the Northwest Territories, Canada, when his private aircraft crashed during his return from a canoe trip.

After graduating, he received job offers from computer companies Control Data and IBM; however, he chose to pursue a Master's degree first.

[6]: 2 [5]: 4  While at IBM, Johnson was limited to working only with components that had already been approved by the company and focused on a narrow section of the circuitry related to the servo system.

Realizing that he had fallen behind in terms of state-of-the-art technology, Johnson spent a year at Memorex learning about circuitry innovations.

[6]: 2 After two years at Memorex, Johnson moved on to a startup called Disk Systems Corporation in the San Francisco Bay Area, a company funded by tape storage manufacturer StorageTek.

[12][13][14] During his five years at StorageTek, Johnson worked as the Program Manager for the 8650 drive, a double density equivalent to the IBM 3350, and then advanced to Director of Engineering for the Disk Division.

[5]: 5 [6]: 2–3 Soon after leaving StorageTek, Johnson met with STC colleague Roy Applequist at the National Computer Conference (NCC) in May 1980, held in Anaheim, to discuss establishing another start-up.

[9]: 40 [5]: 5, 8  In July 1980, Johnson started the disk drive company, MiniScribe, which he initially operated from the basement of his Colorado home, and served as its chief executive officer (CEO) for four years.

[5]: 5–6 [16]: 16–17  He gradually hired five more employees but did not consider his group a successful team until John Squires joined them in January 1981 after leaving StorageTek.

[9]: 41 : 6 [16]: 16 The company had difficulties in persuading vendors to supply components until Johnson secured funding from two major New York-based venture capitalist firms.

When Squires returned to Colorado, Johnson gave him free rein to redesign according to Tandy's specifications, leading to the creation of the Miniscribe 2.

[18][5]: 6 : 16 [6]: 11–12  The IBM contract underpinned the initial product offering (IPO), which raised sufficient capital to invest in building manufacturing capacity.

[20][21][22] A few months later in 1985, John Squires also left Miniscribe and the pair decided to form CoData and build a 3.5" disk drive.

After Squires completed an initial design, Johnson seeking marketing experience contacted Finis Conner, co-founder of Seagate Technology.

[24] After leaving CoData, Terry Johnson persuaded Disk Systems cohort Jim Morehouse to join him in founding PrairieTek in 1986 to build a 2.5" drive, a new form factor aimed at the emerging laptop market.

But Conner Peripherals announced its own 2.5-inch product in early 1990 and by the end of that year had claimed 95 percent of the 2.5-inch drive market.