Some operating systems such as CP/M tracked file length only in units of disk blocks, and used control-Z to mark the end of the actual text in the file.
sˌʌm ˈɑːpɚɹˌeɪɾɪŋ sˈɪstəmz sˈʌtʃ ɐz sˌiːpˈiː slˈæʃ ˈɛm tɹˈækt fˈaɪl lˈɛŋθ ˈoʊnli ɪn jˈuːnɪts ʌv dˈɪsk blˈɑːks, ænd jˈuːzd kəntɹˈoʊlzˈiː tə mˈɑːɹk ðɪ ˈɛnd ʌvðɪ ˈæktʃuːəl tˈɛkst ɪnðə fˈaɪl.