My professional roles include usability consultant, interaction designer, and technical writer. My entire career revolves around the way people are supposed to use software and devices:
1991: I started translating technical documents that were telling people how they were supposed to use products.
1997: I started writing such documents myself.
2000: I started testing with people to see whether they can use products the way they were supposed to.
2003: I started designing interfaces and interactions myself.
2010: I started consulting on ways likely to guarantee products that users can understand and use.
Today: I help building software that people can use (preferably without instructions).
It’s hard. Yet it’s fun.