整数集合上的普通加法运算的幺元是什么，零元是什么？

什么东东啊，能给我中文解释一下吗？

#include <windows.h>
LRESULT CALLBACK WndProc(HWND,UINT,WPARAM,LPARAM);
int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,PSTR szCmdLine,int iCmdShow)
{
static TCHAR szAppNume[]=TEXT("HelloWin");
HWND hWnd;
MSG msg;
WNDCLASS wndclass;
wndclass.style = CS_HREDRAW|CS_VREDRAW;
wndclass.lpfnWndProc = WndProc;
wndclass.cbClsExtra = 0;
wndclass.cbWndExtra = 0;
wndclass.hInstance = hInstance;
wndclass.hIcon = LoadIcon(NULL,IDI_APPLICATION);
wndclass.hCursor = LoadCursor(NULL,IDC_ARROW);
wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
wndclass.lpszMenuName = NULL;
wndclass.lpszClassName = szAppNume;
if(!RegisterClass(&wndclass))
{
MessageBox(NULL,TEXT("This program requires Windows NT!"),szAppNume,MB_ICONERROR);

return 0;
}

hWnd = CreateWindow(szAppNume, //window clas