They use application programs, which in turn use the operating system. But if you're going to develop software for the HP 3000, you should know how to use at least some of MPE's basic programming tools. Sometimes, however, desktop computers and networking services simply aren't available or aren't practical, and you need to fall back on simpler tools. The MPE line editor has been justifiably criticized as being difficult to use, counterintuitive, and just plain old-fashioned. You can buy better editors for the HP 3000.
Alternatives are available at no cost.
In spite of all its shortcomings, however, most HP 3000 programmers sooner or later find it necessary to use the MPE line editor. So apologies having been made, here's a short survival course in using the MPE line editor. Invoking the Editor Log on to the HP 3000 employing a user and account that will give you a colon prompt. You'll be prompted with a line number. You'll now be prompted with another line number.