程序代码：

# include <stdio.h>

int main(void)
{
    int F1=1, F2=1, Fn, n;
    char c;
    printf("斐波那契数列，请输入n值：
");
    scanf("%d", &n);
    if (n == 1)
        printf("该数是1
");
    else if (n == 2)
        printf("该数是1
");
    else
    {
        for (int i=3; i<=n; ++i)
        {
            Fn=F1+F2;
            F1=F2;
            F2=Fn;
        }
        printf("该数是%d
", Fn);
    }
    printf("是否需要将前四十个数字列出？(Y/N)
");
    scanf("%c", &c);//无论是c=getchar(),还是这个，编译器都直接跳过了这一行，为什么？
    if (c == 'Y')
    {
        int F1=1, F2=1, Fn, n=40, i;
        printf("%5d%5d", 1, 1);
        for (i=3; i<=n; ++i)
        {
            Fn=F1+F2;
            F1=F2;
            F2=Fn;
            printf("%5d", Fn);
            if (n%5 == 0)
                printf("
");
        }
    }
    else
        printf("All right
");

    return 0;
}