c语言简简单单的问题

Question

下面虚线内的程序有几处错误

#include<stdio.h>
int main() {
int m = 10;
const int n = 20;
/*---------------------------------------------------------------------------*/
const int *ptr1 = &m;
int * const ptr2 = &m;
*ptr1 = 3;
ptr2 = &n;
int *ptr3 = &n;
const int * ptr4 = &n;
int * const ptr5;
ptr5 = &m;
const int * const ptr6 = &m;
*ptr6 = 5;
ptr6 = &n;
const int * ptr7;
ptr7 = &m;
/*---------------------------------------------------------------------------*/
return 0

求详细解释，刚刚学c。

Answer 1

看编译器提示即可：

编译错误：main.c: In function ‘main’:
main.c:8:7: error: assignment of read-only location ‘*ptr1’
 *ptr1 = 3;
       ^
main.c:9:6: error: assignment of read-only variable ‘ptr2’
 ptr2 = &n;
      ^
main.c:10:13: warning: initialization discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
 int *ptr3 = &n;
             ^
main.c:13:6: error: assignment of read-only variable ‘ptr5’
 ptr5 = &m;
      ^
main.c:15:7: error: assignment of read-only location ‘*ptr6’
 *ptr6 = 5;
       ^
main.c:16:6: error: assignment of read-only variable ‘ptr6’
 ptr6 = &n;
      ^
main.c:20:1: error: expected ‘;’ at end of input
 return 0
 ^~~~~~
main.c:20:1: error: expected declaration or statement at end of input