一些实验性质的程序

#include <stdio.h>
#include <string.h>
#include <stddef.h>
#include "functionProtype.h"
int main()
{
 int b=function1();
 printf("%d/n",b);
 
 printf("%c/n",1+'0');
 //printf("%c",1);
 
 printf("%d/n",fcn(6));
 printf("%d/n/n/n",sum(3,1,2,3));
 
 int a1[5]={1,2,3,4,5};
 
 int *c=a1+3;
 printf("%d/n",c[-1]);
 printf("%d/n",c[-6]);//危险
 
 char arr[]="hello";
 char *arrPoint="hello";
 printf("%s/n",arr);
 printf("%s/n",arrPoint);
 printf("%d/n",sizeof(arr));
 printf("%d/n",sizeof(arrPoint));
 
 char *aa="abc";
 char *bb="abcdef";
 if(strlen(aa)-strlen(bb)>=0)//这一句永远为true,strlen返回值是size_t类型
  printf("hello,yes/n/n");
 
 if(strlen(aa)>strlen(bb))
  printf("this is true");
 
 //size_t类型是一个无符号整型数
 size_t aaa=1;
 size_t bbb=2;
 if(aaa-bbb>=0)//无符号整型数-无符号整型数  不会为负值
  printf("big/n");
 
 unsigned aaaa=1;
 unsigned bbbb=2;
 if(aaaa-bbbb>=0)//无符号整型数-无符号整型数  不会为负值
  printf("big too/n");
 
 //这个匹配就是h中从头往后连续有多少个字符匹配
 char *h=",123789";
 char const *p="123456789";
 int temp=strspn(h,p);
 printf("匹配有%d个/n",temp);
 
}