程序代码：

#include<stdio.h>
#include<stdlib.h>

typedef struct

{
    char *data;
    int length;
}SqString;


int StrAssign(SqString *Sq,char *ch);
void Pri_String(SqString *str);
int main()
{
    SqString str,*sq;
    sq=&str;
    printf("%o\n",&str);
    printf("%o\n",sq);
    StrAssign(sq,"Hello!");
    Pri_String(sq);
    return 0;
}
int StrAssign(SqString *Sq,char *ch)
  /*由串常量ch创建串sq

  1.遍历ch求其长度，对应分配Sq空间
  2.复制，Sq长度*/
{
    printf("1\n");
    char *flag=ch;
    int len;

    while(*flag++!='\0')
        continue;
    len=flag-ch;
    Sq->data=(char *)malloc((len+1)*sizeof(char));
    printf("2\n");
    if(Sq->data==NULL)
    {
        printf("Apply space is not succesed!");
        exit(0);
    }
    while(*(Sq->data)++=*ch++)
        ;
    Sq->length=len;
    printf("3\n");
    return 0;
}
void Pri_String(SqString *str)
{
    for(int i=0;i<str->length;i++)
        putchar(*str->data++);
    printf("\n");
    printf("%s\n",str->data);
    printf("%d\n",str->length);
}