Abstract: A data type detection facility for determining the data type of an incoming stream of data. The characters of the data stream are first tested to determine if they are valid characters of one data type (e.g., EBCDIC). A count of the valid characters is obtained. Then, the data stream is assumed to be of another data type (e.g., ASCII), and the characters of the data stream are translated from that data type to the first data type. After the translation, the same test for valid characters is made and another count is obtained. The two counts are then compared to determine the data type of the data stream.