供参考:
#include <stdio.h>
#include <ctype.h>
int main()
{
char ch, c;
int i, j, n;
while (1)
{
printf("请输入一个字母:");
fflush(stdout); rewind(stdin);
scanf("%c", &ch);
if (isalpha(ch)) break;
}
if (islower(ch))
n = ch - 'a';
else
n = ch - 'A';
for (i = 0; i <= n; i++)
{
for (j = 0, c = ch; j <= i; j++)
printf("%c", c--);
printf("\n");
}
return 0;
}