6. A data processing apparatus according to claim 1, further comprising outputting means for outputting signals corresponding to said first information converted by said converting means.
1. A data processing apparatus comprising: inputting means for inputting alphanumeric character data representing a message to be transmitted; converting means for converting said alphanumeric character data input by said inputting means into first information indicating a series of key operations of a push-button telephone which must be operated by a user when inputting a message corresponding to said alphanumeric character data by said key operations of said push-button telephone connected to a public telephone network; and displaying means for displaying said first information indicating said series of key operations converted by said converting means.