(1)
int main(int argc, char *argv[]) {
int a = 10;
int *c = &a;
cout<<"a: "<<a<<"\t &a:"<<&a<<"\t c:"<<c<<"\t *c:"<<*c<<endl;
*c = 1;
cout<<"a: "<<a<<"\t &a:"<<&a<<"\t c:"<<c<<"\t *c:"<<*c<<endl;
a = 2;
cout<<"a: "<<a<<"\t &a:"<<&a<<"\t c:"<<c<<"\t *c:"<<*c<<endl;
return 0;
}
即：&是获取一个非指针的数据的地址，int a = 10中的a也是相当于一个“指针”指向0x22fd74，c也指向这个区域，一旦一方更改数据则将0x22fd74区域中的值更改了。
(2)
#include <iostream>
#include <string.h>
using namespace std;
/* run this program using the console pauser or add your own getch, system("pause") or input loop */
int add(int a, int b)
{
cout<<"into int add(int a, int b)"<<endl;
cout<<"a: "<<a<<"\t&a: "<<&a<<"\tb: "<<b<<"\tb: "<<&b<<endl;
int i = a;
a = b;
b = i;
cout<<"already,give control to main"<<endl;
cout<<"a: "<<a<<"\t&a: "<<&a<<"\tb: "<<b<<"\tb: "<<&b<<endl;
return a + b;
}
int main(int argc, char *argv[]) {
int a = 1, b = 2, c = 0;
int *ap = &a;
int *bp = &b;
cout<<"a: "<<a<<"\t&a: "<<&a<<"\tb:"<<b<<"\tb: "<<&b<<"\tc:"<<c<<"\t&c: "<<&c<<endl;
cout<<"ap: "<<ap<<"\t*ap: "<<*ap<<"\t&ap: "<<&ap<<endl;
cout<<"bp: "<<bp<<"\t*bp: "<<*bp<<"\t&bp: "<<&bp<<endl;
c = add(a, b);
cout<<"return to main:"<<endl;
cout<<"a: "<<a<<"\t&a: "<<&a<<"\tb: "<<b<<"\tb: "<<&b<<"c: "<<c<<"\t&c: "<<&c<<endl;
return 0;
}
即：在过程调用中的传参数的时候，形参是int型的，则只是传值，被调用过程不会影响调用过程中的参数，因为调用过程中的形参只是对实参的copy，形参和实参的地址是不同的。
（3）
#include <iostream>
#include <string.h>
using namespace std;
/* run this program using the console pauser or add your own getch, system("pause") or input loop */
void add(int a, int b, int c)
{
cout<<"into void add(int a, int b, int c)"<<endl;
cout<<"a: "<<a<<"\t&a: "<<&a<<"\tb: "<<b<<"\tb: "<<&b<<"\tc: "<<c<<"\t&c: "<<&c<<endl;
int i = a;
a = b;
b = i;
c = a + b;
cout<<"already,give control to main"<<endl;
cout<<"a: "<<a<<"\t&a: "<<&a<<"\tb: "<<b<<"\tb: "<<&b<<"\tc: "<<c<<"\t&c: "<<&c<<endl;
}
int main(int argc, char *argv[]) {
int a = 1, b = 2, c = 0;
int *ap = &a;
int *bp = &b;
cout<<"a: "<<a<<"\t&a: "<<&a<<"\tb: "<<b<<"\tb: "<<&b<<"\tc: "<<c<<"\t&c: "<<&c<<endl;
// cout<<"ap: "<<ap<<"\t*ap: "<<*ap<<"\t&ap: "<<&ap<<endl;
// cout<<"bp: "<<bp<<"\t*bp: "<<*bp<<"\t&bp: "<<&bp<<endl;
add(a, b, c);
cout<<"return to main:"<<endl;
cout<<"a: "<<a<<"\t&a: "<<&a<<"\tb: "<<b<<"\tb: "<<&b<<"\tc: "<<c<<"\t&c: "<<&c<<endl;
return 0;
}
原理和2是一样的。
（4）
#include <iostream>
#include <string.h>
using namespace std;
/* run this program using the console pauser or add your own getch, system("pause") or input loop */
int add(int *a, int *b)
{
cout<<"\ninto int add(int *a, int *b)"<<endl;
cout<<"a: "<<a<<"\t&a: "<<&a<<"\t*a: "<<*a<<endl;
cout<<"b: "<<b<<"\t&b: "<<&b<<"\t*b: "<<*b<<endl;
int i = *a;
*a = *b;
*b = i;
cout<<"already,give control to main"<<endl;
cout<<"a: "<<a<<"\t&a: "<<&a<<"\t*a: "<<*a<<endl;
cout<<"b: "<<b<<"\t&b: "<<&b<<"\t*b: "<<*b<<endl;
return *a + *b;
}
int main(int argc, char *argv[]) {
int a = 1, b = 2, c = 0;
int *ap = &a;
int *bp = &b;
cout<<"a: "<<a<<"\t&a: "<<&a<<"\tb: "<<b<<"\tb: "<<&b<<"\tc: "<<c<<"\t&c: "<<&c<<endl;
cout<<"ap: "<<ap<<"\t*ap: "<<*ap<<"\t&ap: "<<&ap<<endl;
cout<<"bp: "<<bp<<"\t*bp: "<<*bp<<"\t&bp: "<<&bp<<endl;
c = add(ap, bp);
// add(&a, &b);
cout<<"\nreturn to main:"<<endl;
cout<<"a: "<<a<<"\t&a: "<<&a<<"\tb: "<<b<<"\tb: "<<&b<<"\tc: "<<c<<"\t&c: "<<&c<<endl;
cout<<"ap: "<<ap<<"\t*ap: "<<*ap<<"\t&ap: "<<&ap<<endl;
cout<<"bp: "<<bp<<"\t*bp: "<<*bp<<"\t&bp: "<<&bp<<endl;
return 0;
}
可以看到在add中a，b和main中的ap，bp的地址不同，但是都是指向0x22fd7c和0x22fd78，所以在add中*a和*b的值交换了，即使得*（0x22fd7c）和*（0x22fd78）交换了，再返回到主函数中，由于a，ap，b，bp，分别指向0x22fd7c和0x22fd78，所以a，*ap，b，*bp的值也改变了。
在这里可以看到一个现象，在add中指针a的地址和指针b的地址和主函数中指针ap和指针bp的地址不一样，其实也是和之前（2），（3）一样，过程调用的时候形参只是复制实参的值，即将地址0x22fd7c和0x22fd78复制到了&a(0x22fc80)和&b(0x22fc88)中，是的*a即是*（0x22fd7c），*b即是*（0x22fd78）。
待续
原文：http://www.cnblogs.com/coralyms/p/4367353.html