A graphics protocol string consists of a partial or complete host message. Each string begins with an ESC Za(enter Graphics mode) command and ends with either an ETB ETX or an ETX character. Terminating a message with ETB ETX indicates a partial message; the remaining text is sent in subsequent messages. The ESC Zb sequence is used to terminate Graphics and return to Text mode.The format for sending a graphic message from the mainframe is:
SOH RID SID DID STX ESC Za (operator)(operand)...ESC Zb ETX