Before reading about building a DDE server or client, become familiar with the following concepts and terms.

| Topic | Item | Format | Data |
|---|---|---|---|
| System | Topics | String | A tab-delimited string of all the topics supported by this server |
| System | Formats | String | A tab-delimited string of all the formats for all items |
| System | SysItems | String | A tab-delimited string of all the items under the System topic |
| System | TopicItemList | String | A tab-delimited string of all the items under the System topic |
| All topics | TopicItemList | String | A tab-delimited string of all the items supported by a topic |
| All topics | Formats | String | A tab-delimited string of all the formats supported by this topic |