WINAPI,请问这5句是什么意思

                  SetMapMode(hdc,MM_ISOTROPIC);
        SetWindowExtEx(hdc,267,72,NULL);
        SetViewportExtEx(hdc,cxClient,cyClient,NULL);
        SetWindowOrgEx(hdc,138,36,NULL);
        SetViewportOrgEx(hdc,cxClient/2,cyClient/2,NULL);