The enclosed source code shows how to control DF from a second application. This example shows two things:
1) It accepts keypresses and forwards them to DF.
2) The "File/Open" menu selection opens and parses a "loadout" file, sending the specified item selections to DF as though you entered them manually.

Notes:
DF needs to be running, though it can be started either before or after this program.
For the "File/Open" (loadout) command, DF needs to be in the item selection screen ("prepare for the journey carefully" then tab to the items screen.) This command will remove the default selections by sending 105 VK_SUBTRACT keypresses (numpad -), then will send the keypresses needed to select the items listed in the loadout file. See loadout.txt for an example.
This only works on Windows.
There is almost no error checking.
This does not directly change DF memory.