The document type is key to determining how Source Insight treats a file. Most importantly, it controls what programming language is associated with each file.
A document type also specifies editing and display options, such as the tab width, word wrap, auto-indentation, display font, and others.
Tip: To see what document type is associated with the current file, right-click on the source file window and select Document Options. The file’s current document type is automatically selected in the dialog box.