1、const定义的值是不可以改变的，类似于java的final
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#include "stdio.h"


main(){
int const x = 15;
x = 16;
printf("%d\n",x);

}

输出：
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pateo@pateo-B86N53X:~/work/study$ cc main.c -o main
main.c: In function ‘main’:
main.c:6: error: assignment of read-only variable ‘x’

2、指针常量
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#include "stdio.h"


main(){
int a=3;
int b=6;
int c=9;

int const *p=&a;
int *const p1=&b;
int const *const p2=&c;

p=&b;
//*p=4;/** 报错，error: assignment of read-only location ‘*p’ **/
a=4;


// p1=&a;/** 报错，error: assignment of read-only location ‘p1’ **/
*p1=5;
b = 7;

p2=&c;/** 报错，error: assignment of read-only location ‘p2’ **/
*p2=8;/** 报错，error: assignment of read-only location ‘*p2’ **/
c = 3;

}

总结：特别是从指针常量的列子中我们基本上能明白const和指针的关系了