程序代码：

#include <stdio.h>
int main()
{
    int i, j, n = 7;
    char I = 'I', ch[6] = "C B C";
    for (i = 0; i < n; i++) {
        if (i == 0 || i == n - 1) {
            for (j = 0; j < 3 * i - 2; j++)
                printf(" ");
            printf("%c\n", I);
        }
        else {
            for (j = 1; j < 3 * i - 2; j++)
                printf(" "); 
            printf("%s\n", ch);
        }
    }
    return 0;
}