Не работает исходник из учебника

#include <Windows.h>
BOOL RegClass(WNDPROC,LPCTSTR,UINT);
LRESULT CALLBACK WndProc(HWND,UINT,WPARAM,LPARAM);
HINSTANCE hInst;
char szClassName[]="WindowAppClass";
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR IpszCmdLine, int nCmdShow)
{
    MSG msg; HWND hwnd; hInst=hInstance;
    if(!RegClass(WndProc,szClassName,COLOR_WINDOW))
        return FALSE;
    hwnd=CreateWindow(szClassName,"App",
        WS_OVERLAPPEDWINDOW|WS_VISIBLE,
        CW_USEDEFAULT,CW_USEDEFAULT,
        CW_USEDEFAULT,CW_USEDEFAULT,
        0,0,hInstance,NULL);
    if(!hwnd) return FALSE;
    while(GetMessage(&msg,0,0,0)) DispatchMessage(&msg);
    return msg.wParam;
}
 
BOOL RegClass(WNDPROC Proc, LPCTSTR szName, UINT brBackground)
{
    WNDCLASS wc; wc.style=wc.cbClsExtra=wc.cbWndExtra=0;
    wc.lpfnWndProc=Proc; wc.hInstance=hInst;
    wc.hIcon=LoadIcon(NULL,IDI_APPLICATION);
    wc.hCursor=LoadCursor(NULL,IDC_ARROW);
    wc.hbrBackground=(HBRUSH)(brBackground+1);
    wc.lpszMenuName=NULL; wc.lpszClassName=szName;
    return (RegisterClass(&wc)!=0);
}
 
LRESULT CALLBACK WndProc(HWND hwnd,UINT msg,WPARAM wParam,LPARAM lParam)
{
    switch (msg)
    {case WM_DESTROY:{PostQuitMessage(0);return 0;}}
    return DefWindowProc(hwnd,msg,wParam,lParam);