afxdata是一个全局变量，MFC用它来记录系统信息，如版本信息等。它定义在AFXIMPL.H中。

struct AUX_DATA

{

// system metrics

int cxVScroll, cyHScroll;

int cxIcon, cyIcon;

int cxBorder2, cyBorder2;

// device metrics for screen

int cxPixelsPerInch, cyPixelsPerInch;

// convenient system color

HBRUSH hbrWindowFrame;

HBRUSH hbrBtnFace;

// color values of system colors used for CToolBar

COLORREF clrBtnFace, clrBtnShadow, clrBtnHilite;

COLORREF clrBtnText, clrWindowFrame;

// standard cursors

HCURSOR hcurWait;

HCURSOR hcurArrow;

HCURSOR hcurHelp; // cursor used in Shift+F1 help

// special GDI objects allocated on demand

HFONT hStatusFont;

HFONT hToolTipsFont;

HBITMAP hbmMenuDot;

// other system information

UINT nWinVer; // Major.Minor version numbers

BOOL bWin95; // TRUE if Windows 95 (not NT)

BOOL bWin4; // TRUE if Windows 4.0

BOOL bNotWin4; // TRUE if not Windows 4.0

BOOL bSmCaption; // TRUE if WS_EX_SMCAPTION is supported

BOOL bMarked4; // TRUE if marked as 4.0

// Implementation

AUX_DATA();

~AUX_DATA();

void UpdateSysColors();

void UpdateSysMetrics();

};

extern AFX_DATA AUX_DATA afxData;