CALCUL D'UNE RACINE NUMÉRIQUE

#include <windows.h>
#include "resource.h"

int ranum(const char *n) { // Racine numérique de n
    char buf[32];
    int i, s = 0;
    for(i = 0; isdigit(n[i]); i++) s = s + n[i] - '0';
    if(s < 10) return s;
    wsprintf(buf, "%d", s);
    return ranum(buf);
}

BOOL APIENTRY DlgProc(HWND hDlg,UINT uMsg,WPARAM wParam,LPARAM lParam) {
    CHAR nb[21], res[81];
    switch (uMsg) {
        case WM_INITDIALOG:
            return TRUE;
        case WM_COMMAND:
            if (LOWORD(wParam) == IDOK) {
                GetDlgItemText(hDlg, IDE_EDIT1, nb, 20);
                wsprintf(res, "Racine numérique de : %s = %d", nb, ranum(nb));
                MessageBox(hDlg, res, "Résultat", MB_OK);
            }
            if (LOWORD(wParam) == IDCANCEL) {
                EndDialog(hDlg,0);
                return TRUE;
            }
        default:
            return FALSE;
    }
}

int WINAPI WinMain(HINSTANCE hInstance, 
                   HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) {
    DialogBox(hInstance,"DIALOG1",NULL,(DLGPROC)DlgProc);
    return 0;
}