7.1.1 Message Processing
Where do messages come from, and what kinds of information do
they convey? Windows defines hundreds of different message
types. Most messages have names that begin with the letters
"WM" and an underscore, as in WM_CREATE and
WM_PAINT.
One way to characterize a Windows program is to think of it as a
collection of message handlers. To a large extent, it is a program's
unique way of responding to messages that gives it its personality.
typedef struct tagMSG {
HWND hwnd;
UINT message;
WPARAM wParam;
LPARAM lParam;
DWORD time;
POINT pt;
} MSG;
