#include <stdio.h>
#define N 15
#define M ((int)(sizeof(b)/sizeof(b[0])))
int main(void)
{
    char a[N],ch,b[10]={0};
    int i,j=0,k;
    printf("Enter a first and last name:");
    k=0;
    do {                                  //读取名
        i =getchar();
        a[k] =i;
        k++;
        }while(i!= ' ');
    j=0;
    while((ch=getchar())!='\n')            //读取姓氏
    {
        b[j]=ch;
        j++;
    }
        printf("You enered the name:");
    for(j=0;j<M;j++)                         //输出姓氏，此处的M我想指定循环的次数，但是不能实现，请请教。
    {
        printf("%c",b[j]);
    }
        printf(",%c.",a[0]);
        printf("%d",M);
    return 0;
}


输出示例：
   Enter a first and last name:Lloyd Fosdick
   You enterd the name: Fosdick,L.