程序代码：

/*
http://bbs.bccn.net/thread-439898-1-1.html
*/

#include <stdio.h>
#include <stdlib.h>
#include <conio.h>

const size_t Rows = 5;
const size_t Cols = 5;
const int Data[Rows][Cols] = {
    {  1,  2,  3,  4,  5 },
    {  6,  7,  8,  9, 10 },
    { 11, 12, 13, 14, 15 },
    { 16, 17, 18, 19, 20 },
    { 21, 22, 23, 24, 25 }
};
/*
const int Data[Rows][Cols] = {
    { 12, 56, 34, 56, 34 },
    { 13, 45, 67, 45, 67 },
    { 34, 67, 54, 67, 78 },
    { 34, 56, 78, 89, 9 },
    { 34, 56, 78, 9, 56 }
};
*/

void Pause(void);
void ShowData(void);
void GetResult(int* result1, int* result2);

int main(void)
{
    ShowData();
    putchar('\n');

    int result1, result2;
    GetResult(&result1, &result2);
    printf_s("两条对角线上各元素之和 = %d\n", result1);
    printf_s("两条对角线上行、列下标均为偶数的各元素之积 = %d\n", result2);

    Pause();
    return EXIT_SUCCESS;
}

void Pause(void)
{
    printf_s("\nPress any key to continue...");
    _getch();
}

void ShowData(void)
{
    for (size_t row = 0; row < Rows; ++row)
    {
        for (size_t col = 0; col < Cols; ++col)
        {
            printf_s("%02d", Data[row][col]);
            if (col < Cols - 1)
            {
                putchar(' ');
            }
        }
        putchar('\n');
    }
}

void GetResult(int* result1, int* result2)
{
    *result1 = 0;
    *result2 = 1;

    for (size_t row =0; row < Rows; ++row)
    {
        for (size_t col = 0; col < Cols; ++col)
        {
            if (row == col)
            {
                //printf_s("%02d ", Data[row][col]);
                *result1 += Data[row][col];
                if ((row % 2 == 0) && (col % 2 == 0))
                {
                    //printf_s("%02d ", Data[row][col]);
                    *result2 *= Data[row][col];
                }
            }
            if (col == Cols - row - 1)
            {
                //printf_s("%02d ", Data[row][col]);
                *result1 += Data[row][col];
                if ((row % 2 == 0) && (col % 2 == 0))
                {
                    //printf_s("%02d ", Data[row][col]);
                    *result2 *= Data[row][col];
                }
            }
        }
    }
}