With the other special characters and control codes filled in, ASCII was published as ASA X3.4-1963, leaving 28 code positions without any assigned meaning, reserved for future standardization, and one unassigned control code.
wɪððɪ ˈʌðɚ spˈɛʃəl kˈæɹɪktɚz ænd kəntɹˈoʊl kˈoʊdz fˈɪld ˈɪn, ˈæski wʌz pˈʌblɪʃt æz ˌeɪˌɛsˈeɪ ˈɛks θɹˈiː.fˈoːɹ dˈæʃ nˈaɪntiːnhˈʌndɹɪd sˈɪksti θɹˈiː, lˈiːvɪŋ twˈɛnti ˈeɪt kˈoʊd pəzˈɪʃənz wɪðˌaʊt ˌɛni ɐsˈaɪnd mˈiːnɪŋ, ɹɪzˈɜːvd fɔːɹ fjˈuːtʃɚ stˌændɚdᵻzˈeɪʃən, ænd wˈʌn ʌnɐsˈaɪnd kəntɹˈoʊl kˈoʊd.