I am using Delphi from within Rad Studio 10.2 to write a small program to see exactly how to talk to a device via USB. The device will appear as a Com port. I have a working shell for my program and started to write in the details for how to open, configure, write to, and close a port. I started with close because it is the smallest. I am getting the error message undeclared identifier 'CloseHandle'. Is there a UNIT I need to add to USES ?