In addition to pre-defined status and action flags for communicating with the command processors, TRANSMIT and RECEIVE exits can use several other parameters to communicate between themselves, the issuers of TRANSMIT and RECEIVE, and the command processors. Those parameters include the:

• Exit-to-exit communication word. The TRANSMIT and RECEIVE command processors pass to each exit an exit-to-exit communication word. The exits can use that word to communicate among themselves by passing information in the storage to which the word points. The startup or initialization exit needs to obtain the block of storage and store its address in the exit-to-exit communication word. TRANSMIT and RECEIVE initially set the word to zero, and thereafter do not modify it or the contents of the storage to which it points.
• PARM keyword on the TRANSMIT and RECEIVE commands. TRANSMIT and RECEIVE both have PARM keywords on which the issuer can specify a string of up to 247 bytes. All exits receive the string in their parameter lists, and can act differently for different PARM values. The installation needs to tell intended users what PARM values to specify.
• PARM tag in NAMES.TEXT data set entries. Some TRANSMIT and RECEIVE exits can also access a copy of the user string specified on the :PARM tag in the addressee's nickname entry in the sender's NAMES.TEXT data set. The string can be up to 30 bytes long. The PARM tag provides a way for users to request, and exits to provide, different processing for different users. The installation needs to tell intended users what PARM values to specify.
• A notification string that the TRANSMIT initialization exit passes to the RECEIVE notification and the RECEIVE acknowledgment notification exits. If the sender requested acknowledgment, the string is also returned to the sender after RECEIVE processing completes. It provides a means of tracking the receipt of specific transmissions, or triggering specific exit actions. The string can be up to 64 bytes long.
• A user string that the TRANSMIT initialization exit passes to the RECEIVE pre-processing, post-prompt, post-processing, and decryption exits. The string can be up to 247 bytes long.