The Structure of GDI
From the programmer’s perspective, GDI consists of several hundred function calls and some associated data types, macros, and structures. But before we begin looking at some of these functions in detail, let’s step back and get a feel for the overall structure of GDI.
The GDI Philosophy
Graphics in Windows 98 and Microsoft Windows NT is handled primarily by functions exported from the dynamic-link library GDI32.DLL. In Windows 98, this GDI32.DLL makes use of the 16-bit GDI.EXE dynamic-link library for the actual implementation of many of the functions. In Windows NT, GDI.EXE is used only for 16-bit programs.
These dynamic-link libraries call routines in device drivers for the video display and any printers you may have set up. ...