请问下面两段之间是什么关系呢，查资料越看越糊涂了……谢谢大家！
typedef struct{
REGION_T region;
int (* dot)(int ,int ,COLOR_T /* c */);
int (* line)(int /* x0 */,int /* y0 */,int /* x1 */,int /* y1 */,COLOR_T c);
int (* rect)(RECT_T * /* r */);
int (* box)(BOX_T * /* b */ );
int (* set_cursor)(int /* x */,int /* y */);
int (* line_to)(int /* x */,int /* y */,COLOR_T /* c */);
int (* arrow)(int x,int y,int dir,COLOR_T c);
int (* processbar)(PROCESSBAR_T *);
int (* splitter)(SPLITTER_T *);
int (* check_box)(CHECK_BOX_T *);
int (* circle)(int x,int y,int r,int fill,COLOR_T c);
int (* scrollbar)(SCROLLBAR_T *);
int (* show_picture)(int x,int y,int width,int height,char * path);
int (* dialog)(const char * fmt,...);
}GUI_T;



static int dot(int x, int y, COLOR_T c);
static int line(int /* x0 */, int /* y0 */, int /* x1 */, int /* y1 */, COLOR_T);
static int rect(RECT_T *);
static int box(BOX_T *);
static int line_to(int /* x */, int /* y */, COLOR_T /* c */);
static int set_cursor(int /* x */, int /* y */);
static int draw_arrow(int x, int y, int dir, COLOR_T c);
static int processbar(PROCESSBAR_T *);
static int splitter(SPLITTER_T *);
static int check_box(CHECK_BOX_T *);
static int circle(int x, int y, int r, int fill, COLOR_T c);
static int scrollbar(SCROLLBAR_T *);
static int show_picture(int x,int y,int width,int height,char * path);