程序代码：

#include <Windows.h>
#include <cstdio>
#include <cstring>
#include <cctype>
#include <conio.h>

HANDLE hOutput;

const int K_BACKSPACE = 0x08;
const int K_ENTER     = 0x0D;

void Pause(void);
void ClearScreen(void);
void GotoXY(short x, short y);
void GotoXY(COORD pos);

void main(void)
{
    hOutput = GetStdHandle(STD_OUTPUT_HANDLE);
    if (hOutput == INVALID_HANDLE_VALUE)
    {
        return;
    }

    ClearScreen();
    const size_t length = 8;
    char message[] = "请输入密码: ";
    COORD pos = { 5, 5 };
    GotoXY(pos);
    printf_s("%s________", message);
    GotoXY(pos.X + strlen(message), pos.Y);
    int ch;
    size_t counter = 0;
    char password[length];
    do
    {
        ch = _getch();
        switch (ch)
        {
            case 0xE0:
                ch = _getch();
                break;
            case K_BACKSPACE:
                --counter;
                CONSOLE_SCREEN_BUFFER_INFO info;
                GetConsoleScreenBufferInfo(hOutput, &info);
                GotoXY(info.dwCursorPosition.X - 1, info.dwCursorPosition.Y);
                _putch('_');
                GotoXY(info.dwCursorPosition.X - 1, info.dwCursorPosition.Y);
                break;
            default:
                if (isalnum(ch))
                {
                    password[counter++] = ch;
                    _putch('*');
                    if (counter >= length)
                    {
                        ch = K_ENTER;
                    }
                }
                break;
        }
    } while (ch != K_ENTER);
    password[counter] = '\0';
    GotoXY(pos.X, pos.Y + 1);
    printf_s("您输入的密码是: %s", password);

    Pause();
}

void Pause(void)
{
    GotoXY(0, 24);
    printf_s("Press any key to continue...");
    _getch();
}

void ClearScreen(void)
{
    CONSOLE_SCREEN_BUFFER_INFO info;
    DWORD number;
    COORD pos = { 0, 0 };
    GetConsoleScreenBufferInfo(hOutput, &info);
    FillConsoleOutputCharacterA(hOutput, ' ', info.dwSize.X * info.dwSize.Y, pos, &number);
    GotoXY(pos);
}

void GotoXY(COORD pos)
{
    SetConsoleCursorPosition(hOutput, pos);
}

void GotoXY(short x, short y)
{
    COORD pos = { x, y };
    SetConsoleCursorPosition(hOutput, pos);
}