The sign big-notes BASIC
BASIC only became "the standard way people ... learned to program" for those who had no standards.
Its legacy has been to give an erroneous impression of how programming should be done to many people outside the field, including those who get into decision-making positions where they can be responsible for spending large sums of public money on software. Programming should not be an endless quagmire of spaghetti code, punctuated by panicked edits and reruns. What might have been excusable in the 1950s had no business existing by the 1980s.
The sign needed only one word:
"DIM"