in: a type of establishment I work in a software company
an industry I work in computers
on: a task I work on writing documentation
at: a specific establishment I work at BART, Inc.
with: used with the verb “to be” I worked at Multimedia, GmbH for two years. I am now with BART, Inc.
for: used to refer to I work for BART, Inc.
part-time, temporary, or off-site relationships