Pointer parameter, level two pointer change value

Program:

#include <stdio.h>#include<stdlib.h>voidChangeChar*a) {//Copyprintf"Change 1:%s\n", a); A=" Change";//The argument copy points to a change without affecting the point of the argumentprintf"Change 2:%s\n", a);}voidChange2 (Char**a) {printf ("Change2 1:%s\n", *a); *a="Changea";//A is unchanged, changes a to the contents of the memory, a pointing to the memory is pointer A, changing the pointer a point, the original pointer A to the content is unchangedprintf"Change2 2:%s\n", *a);}voidChange3 (Char*a) {printf ("Change3 1:%s\n", a); //Char *b= (char *) malloc (sizeof (char) *10);//malloc allocates heap memory (but B itself is in the stack.) Stack allocation: char b[10], function return is released), unless the program exits without free//a=b;sscanf"Changeb","%s", a);//directly change the value of a point to addressprintf"Change3 2:%s\n", a); //Free (b);}voidChange4 (int*a) {//Copyprintf"change4 1:%d\n", *a); intb= the; A=&b;//with a copy of the argument, the copy points to a change, but does not affect the point of the original argument. Unless you change the value that the original argument points to, that is Change5printf"change4 2:%d\n", *a);}voidChange5 (int*a) {printf ("change5 1:%d\n", *a); *a= the;//A does not change the content of a pointing to memoryprintf"change5 2:%d\n", *a);}voidChange6 (int**a) {    intb= -; printf ("Change6 1:%d\n", **a); *a=&b;//the same as Change2 .printf"Change6 2:%d\n", **a);}intMain () {//    Char*a ="Main"; Char*a1=A; Change (a);//Pass in a first-level pointer, which is a copy of the pointer within the functionprintf"Main 1:%s\n\n", a);//no change, here is mainChange2 (&AMP;A);//Pass in a level two pointerprintf"Main 2:%s\n", a);//change to the value given in Change2printf"Main 2 a1:%s\n\n", A1);//Change2 just points a back to the new value, and the value pointed to by A1 is constant.    Charb[Ten] ="mainb";//cannot be here char *b, and the function does not allocate memory, otherwise sscanf error segment Spit Core//char *b= "XX";Change3 (b); printf ("Main 3:%s\n\n", b);//change the value given to sscanf in Change3    intC= -; Change4 (&c); printf ("Main 4:%d\n\n", c);//no change, or a.Change5 (&c); printf ("Main 5:%d\n\n", c);//change the new value given to Change5    int*d=&c;//the same as Change2 .    int*d1=D; Change6 (&AMP;D);//Pass in a level two pointerprintf"Main 6:%d\n", *d);//Changeprintf"Main 5:%d\n\n", *D1);//Original C value    return 0;}

Results:

Pointer parameter, level two pointer change value