In English the past tense is formed by adding
ed to the base verb form in
affirmative sentences. In
negations you always get
didn't and the
base verb form. In
questions you always get
did and the
base verb form.
PRESENT - PAST
walk -- walked
don't walk -- didn't walk
doesn't walk -- didn't walk
Do...walk? -- Did...walk?
Does...walk? -- Did...walk?