根据文档要求，将所有.c和.h的文件以及所有需要的代码都写出来

基于提供的描述，下面提供一个基础框架来满足需求的功能，即当按下矩阵中的按键后，蜂鸣器发声并且数码管显示出相应的编号值。请注意，实际的编程环境可能需要不同的头文件或函数定义，此示例仅作为参考：

**matrix_keys.c**

#include "matrix_keys.h"
unsigned char key;
unsigned char beep;

void matrixScan(void)
{
    P2 = 0x7E; 
    unsigned char temp = P2; 
    temp &= 0x70;
    
    // debounce and detect pressed keys
    if (temp != 0x70)
    {
        delay(10);
        
        if (temp != 0x70)
        {
            temp = P2;
            
            switch (temp)
            {
                case 0x6E: key = 1; beep = 1; delay(100); beep = 0; break;
                case 0x5E: key = 5; beep = 1; delay(100); beep = 0; break;
                case 0x3E: key = 8; beep = 1; delay(100); beep = 0; break;
                default: break;   // handle other cases if necessary
            }
        }
    }

    while (temp != 0x70)
    {
        temp = P2;
        temp &= 0x70;
    }

    beep = 0;
}

**buzz.c**

#include "buzz.h"

void buzzOn()
{
    P5 ^= 4;     // Turn on buzzer
}

void buzzOff()
{
    P5 &= ~4;    // Turn off buzzer
}

**display.c**

#include "display.h"

// This is a very simplified function for demonstration purposes.
// Actual implementation would be more complex.
void displayNumber(unsigned char number)
{
    // Implement the logic to light up appropriate segments of the LED digits based on 'number'
}

**main.c**

#include <reg51.h>
#include "matrix_keys.h"
#include "buzz.h"
#include "display.h"

void main(void)
{
    while (1)
    {
        matrixScan();
        if (key > 0)
        {
            buzzOn();  // Make buzzer sound
            displayNumber(key);  // Display the corresponding number on the LED digits
            delay(500);  // A longer delay so that we can see the digit
            buzzOff();  // Stop the buzzer from sounding
        }
    }
}

**matrix_keys.h**

#ifndef MATRIX_KEYS_H_
#define MATRIX_KEYS_H_

extern unsigned char key;
extern unsigned char beep;

void matrixScan(void);

#endif /* MATRIX_KEYS_H_ */

**buzz.h**

#ifndef BUZZ_H_
#define BUZZ_H_

void buzzOn(void);
void buzzOff(void);

#endif /* BUZZ_H_ */

**display.h**

#ifndef DISPLAY_H_
#define DISPLAY_H_

void displayNumber(unsigned char number);

#endif /* DISPLAY_H_ */

以上代码仅供参考，实际使用时可能需要调整以适应具体的硬件环境和编译器特性。每个模块被设计成独立且可重用的形式。`main()`函数中包含了主循环逻辑，它调用其他函数来检测键输入、启动蜂鸣器并更新LED数字显示器的状态。`matrixScan()`负责读取键盘状态并确定哪个键被按下了；`buzzOn()`和`buzzOff()`用于控制蜂鸣器；而`displayNumber()`则应根据传入的数字参数点亮正确的LED段落。