编写MCS-51单片机控制程序，利用矩阵键盘以及LED数码管，实现输入按键序号的显示。

好的，下面是一个简单的MCS-51单片机控制程序，可以实现您的要求。假设您使用的是4x4矩阵键盘和共阳极LED数码管。代码如下：

#include <reg51.h> // 引入单片机头文件

sbit ROW1 = P1^0; // 定义行引脚
sbit ROW2 = P1^1;
sbit ROW3 = P1^2;
sbit ROW4 = P1^3;
sbit COL1 = P1^4; // 定义列引脚
sbit COL2 = P1^5;
sbit COL3 = P1^6;
sbit COL4 = P1^7;
sbit LED_A = P2^0; // 定义LED数码管引脚
sbit LED_B = P2^1;
sbit LED_C = P2^2;
sbit LED_D = P2^3;
sbit LED_E = P2^4;
sbit LED_F = P2^5;
sbit LED_G = P2^6;
sbit LED_DP = P2^7;

unsigned char key_value = 0; // 定义按键值
unsigned char LED_num = 0; // 定义LED数码管显示的数字

void delay(unsigned int t) // 延时函数
{
    unsigned int i, j;
    for (i = t; i > 0; i--)
        for (j = 110; j > 0; j--);
}

void scan_key() // 矩阵键盘扫描函数
{
    ROW1 = 0; ROW2 = 1; ROW3 = 1; ROW4 = 1; // 第1行扫描
    if (COL1 == 0) key_value = 1;
    else if (COL2 == 0) key_value = 2;
    else if (COL3 == 0) key_value = 3;
    else if (COL4 == 0) key_value = 10;
    ROW1 = 1; ROW2 = 0; ROW3 = 1; ROW4 = 1; // 第2行扫描
    if (COL1 == 0) key_value = 4;
    else if (COL2 == 0) key_value = 5;
    else if (COL3 == 0) key_value = 6;
    else if (COL4 == 0) key_value = 11;
    ROW1 = 1; ROW2 = 1; ROW3 = 0; ROW4 = 1; // 第3行扫描
    if (COL1 == 0) key_value = 7;
    else if (COL2 == 0) key_value = 8;
    else if (COL3 == 0) key_value = 9;
    else if (COL4 == 0) key_value = 12;
    ROW1 = 1; ROW2 = 1; ROW3 = 1; ROW4 = 0; // 第4行扫描
    if (COL1 == 0) key_value = 14;
    else if (COL2 == 0) key_value = 0;
    else if (COL3 == 0) key_value = 15;
    else if (COL4 == 0) key_value = 13;
}

void display_LED() // LED数码管显示函数
{
    switch (LED_num) // 根据数字选择显示的LED段
    {
        case 0: LED_A = LED_B = LED_C = LED_D = LED_E = LED_F = 1; LED_G = 0; break;
        case 1: LED_B = LED_C = 1; LED_A = LED_D = LED_E = LED_F = LED_G = 0; break;
        case 2: LED_A = LED_B = LED_G = LED_E = LED_D = 1; LED_C = LED_F = 0; break;
        case 3: LED_A = LED_B = LED_G = LED_C = LED_D = 1; LED_E = LED_F = 0; break;
        case 4: LED_F = LED_G = LED_B = LED_C = 1; LED_A = LED_D = LED_E = 0; break;
        case 5: LED_A = LED_F = LED_G = LED_C = LED_D = 1; LED_B = LED_E = 0; break;
        case 6: LED_A = LED_F = LED_G = LED_E = LED_D = LED_C = 1; LED_B = 0; break;
        case 7: LED_A = LED_B = LED_C = 1; LED_D = LED_E = LED_F = LED_G = 0; break;
        case 8: LED_A = LED_B = LED_C = LED_D = LED_E = LED_F = LED_G = 1; break;
        case 9: LED_A = LED_B = LED_C = LED_D = LED_F = LED_G = 1; LED_E = 0; break;
        case 10: LED_A = LED_B = LED_C = LED_D = LED_E = LED_F = LED_G = 0; break;
        case 11: LED_A = LED_B = LED_C = LED_D = LED_E = LED_F = LED_G = 0; LED_DP = 1; break;
        case 12: LED_A = LED_B = LED_C = LED_D = LED_E = LED_F = LED_G = 0; LED_DP = 0; break;
        case 13: LED_A = LED_B = LED_C = LED_D = LED_E = LED_F = 0; LED_G = 1; break;
        case 14: LED_A = LED_B = LED_C = LED_D = 0; LED_E = LED_F = LED_G = 1; break;
        case 15: LED_A = LED_D = LED_E = LED_F = LED_G = 1; LED_B = LED_C = 0; break;
    }
}

void main() // 主函数
{
    while (1)
    {
        scan_key(); // 扫描矩阵键盘
        if (key_value != 0) // 如果有按键按下
        {
            if (key_value == 10) LED_num = 0; // 如果按下的是0键
            else LED_num = key_value; // 其他键直接赋值给LED数码管
        }
        display_LED(); // 显示LED数码管
        delay(5); // 延时
    }
}

注释已经写得比较详细了，您可以根据代码进行调试和修改。另外，由于您没有提供具体的硬件连接方式，所以这里的引脚定义仅供参考。如果您的硬件连接方式不同，需要根据实际情况进行修改。