代码

void TC_const(void){    char *a;    char * const   p1        = "char * const   p1;        //const     pointer, non-const data";    char   const * p2        = "char   const * p2;        //non-const pointer,     const data";    const   char * p22       = "const  char  * p22;       //non-const pointer,     const data";    char   const * const p3  = "char   const * const p3;  //const pointer,         const data";    const  char  * const p33 = "const  char  * const p33; //const pointer,         const data";    printf("%s\n", p1);    printf("%s\n", p2);    printf("%s\n", p3);    p1[0]  = 1;   // ok    p1     = a;  //  error: assignment of read-only variable 'p1'    p2[0]  = 2;   // error: assignment of read-only location '*p2'    p22[0] = 2;   // error: assignment of read-only location '*p22'    p2     = a;   // ok;    p22    = a;   // ok;    p3[0]  = 3;   // error: assignment of read-only location '*p3'    p33[0] = 3;   // error: assignment of read-only location '*p33'    p3     = a;   // error: assignment of read-only variable 'p3'    p33    = a;   // error: assignment of read-only variable 'p33'}

Code::Blocks 17.12 编译提示

mingw32-gcc.exe -Wall -g  -c X:\sz\2018\c-exp@CodeBlockIDE\ex1-vprintf\vprintf\main.c -o obj\Debug\main.omingw32-g++.exe  -o bin\Debug\vprintf.exe obj\Debug\main.o   X:\sz\2018\c-exp@CodeBlockIDE\ex1-vprintf\vprintf\main.c: In function 'TC_const':X:\sz\2018\c-exp@CodeBlockIDE\ex1-vprintf\vprintf\main.c:30:9: error: assignment of read-only variable 'p1'  p1     = a;  //  error: assignment of read-only variable         ^X:\sz\2018\c-exp@CodeBlockIDE\ex1-vprintf\vprintf\main.c:33:9: error: assignment of read-only location '*p2'  p2[0]  = 2;   //  error: assignment of read-only variable         ^X:\sz\2018\c-exp@CodeBlockIDE\ex1-vprintf\vprintf\main.c:34:9: error: assignment of read-only location '*p22'  p22[0] = 2;   //  error: assignment of read-only variable         ^X:\sz\2018\c-exp@CodeBlockIDE\ex1-vprintf\vprintf\main.c:38:9: error: assignment of read-only location '*p3'  p3[0]  = 3;   //  error: assignment of read-only variable         ^X:\sz\2018\c-exp@CodeBlockIDE\ex1-vprintf\vprintf\main.c:39:9: error: assignment of read-only location '*p33'  p33[0] = 3;   //  error: assignment of read-only variable         ^X:\sz\2018\c-exp@CodeBlockIDE\ex1-vprintf\vprintf\main.c:40:9: error: assignment of read-only variable 'p3'  p3     = a;  // error: assignment of read-only variable 'p3'|         ^X:\sz\2018\c-exp@CodeBlockIDE\ex1-vprintf\vprintf\main.c:41:9: error: assignment of read-only variable 'p33'  p33    = a;  // error: assignment of read-only variable 'p3'|         ^X:\sz\2018\c-exp@CodeBlockIDE\ex1-vprintf\vprintf\main.c: In function 'colorAtLinux':

总结

以*为基准，

1. const在*的右边出现时，表示指针变量本身是一个常量，可以叫指针常量，其值（指向的地址）不可改变，但指向地址的内容可以改变。
2. const在*的左边出现时，表示指针变量本身是一个变量，可以叫指针变量，其值（指向的地址）可以改变，但指向地址的内容不可改变。
3. 两边都出现时，则其值（指向的地址）不可改变，且指向地址的内容也不可改变。

环境

WINDOWS2016

Code::Block 17.12