System Topic

We recommend that all server applications support the system topic. This is a special topic that most servers support to provide a way for a client to interrogate the server on the following:

•Other topics it supports.

•Items that can be used with the system topic.

•Formats that it understands.

Guarded Blocks        

Use stimulus on hold (make stimulus disposition action routine) before entering guarded blocks that do not contain DDE stimulus responses.

ESL DDE Conversation

It is not possible for a particular instance of an ESL  application to establish a DDE conversation with itself, however, an ESL program can establish a conversation with one or more other instances of itself.

The maximum length of data that can be transferred in a single DDE exchange is (65,522 - (length of ItemName)) bytes.