请教高手一个有关C51指针的问题

dubuguyun

在C51的说明文档里面，有这么这么两段：
“
Abstract pointer types are described here using code examples with the following variables.
char xdata *px;       /* ptr to xdata */char idata *pi;       /* ptr to idata */char code  *pc;       /* ptr to code  */”与：“Memory-specific pointers always include a memory type specification in the pointer declaration and always refer to a specific memory area. For example:
char data *str;        /* ptr to string in data */int xdata *numtab;     /* ptr to int(s) in xdata */long code *powtab;     /* ptr to long(s) in code */ ”我的问题是这两个的确切的区别是怎么理解的呢？谢谢各位指教！

dubuguyun

C51说明里有这么两段：
Memory-specific pointers always include a memory type specification in the pointer declaration and always refer to a specific memory area. For example:

char data *str;        /* ptr to string in data */
int xdata *numtab;     /* ptr to int(s) in xdata */
long code *powtab;     /* ptr to long(s) in code */

和

Abstract pointer types are described here using code examples with the following variables.

char xdata *px;       /* ptr to xdata */
char idata *pi;       /* ptr to idata */
char code  *pc;       /* ptr to code  */


我的问题是这两段的确切区别是怎么理解的？谢谢各位的指教！