In its current release, HyperDA does not support XCMDs and XFCNs written outside HyperTalk and copied into the stack. If such commands and functions are encountered in scripts by HyperDA, they are simply ignored just as if they were legal but unsupported HyperTalk commands. As a Desk Accessory, HyperDA exists only inside a running application. On the other hand, external commands and functions (XCMDs and XFCNs) work asynchronously with HyperCard stacks. When HyperCard encounters an XCMD or XFCN, it simply turns over control to that routine and waits for it to finish executing. To grant this same level of control to a program running inside a Desk Accessory would be extremely dangerous. An XCMD or XFCN might want to do something that is completely illegal or irrational in a HyperDA environment that would be perfectly understandable and acceptable under HyperCard itself.
