FILE *fp文件指针
fp=fopen("1.txt","w+);//r+,rw
if(fp==NULL)：判断要写
{printf("open filed!")}
int a=10;
int b;
fprintf(fp,"%d",a)
fscanf(fp,"%d",&b)
fclose(fp)
printf("%d",b)
/0覆盖不了当前字符
fputs(s,fp)
fgets(ss,5,fp)
fseek(fp,-2,seek_END)从最后往前移动2个单位
typedef 定义一个别名
