Address 413 of the Abort Guidance System (AGS) contained the variable that indicated the LM had landed.
ɐdɹˈɛs fˈoːɹhˈʌndɹɪd θˈɜːtiːn ʌvðɪ ɐbˈɔːɹt ɡˈaɪdəns sˈɪstəm ˌeɪdʒˌiːˈɛs kəntˈeɪnd ðə vˈɛɹɪəbəl ðæt ˈɪndᵻkˌeɪɾᵻd ðɪ ˌɛlˈɛm hæd lˈændᵻd.