ABCDEFEDCBA ABCDE EDCBA ABCD DCBA ABC CBA AB BA A A.

#include <stdio.h>

int main(void)
{
int i, j, k;
char ch;

i = 0;
while(i <= 5)
{
j = 5;
ch = 'A';
printf("\n");
while(j >= i)
{
printf("%c", ch);
j--;
ch++;
}
j = 1;
while(j <= (2 * i - 1))
{
printf(" ");
j++;
}
if(i == 0) ch -= 2;
else ch--;
while(ch >= 'A')
{
printf("%c", ch);
ch--;
}
i++;
}

return 0;
}