#include <iostream>
using namespace std;
class Temp {
        public:
                static Temp * getInstance();
                static void putInstance();
        private:
                static Temp *instance;
};
Temp * Temp::getInstance()
{
        if (!instance)
                instance = new Temp();
        return instance;
}
void Temp::putInstance()
{
        if (instance) {
                delete instance;
                instance = NULL;
        }  
}
int main()
{
        Temp *p;
        p = Temp::getInstance();
        return 0;
}

＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝
上面的程序报错：
/tmp/ccpL8OB4.o: In function `Temp::putInstance()':
hello.cpp:(.text+0x79): undefined reference to `Temp::instance'
hello.cpp:(.text+0x82): undefined reference to `Temp::instance'
hello.cpp:(.text+0x90): undefined reference to `Temp::instance'
/tmp/ccpL8OB4.o: In function `Temp::getInstance()':
hello.cpp:(.text+0xa1): undefined reference to `Temp::instance'
hello.cpp:(.text+0xb6): undefined reference to `Temp::instance'
/tmp/ccpL8OB4.o:hello.cpp:(.text+0xbb): more undefined references to `Temp::instance' follow
collect2: ld returned 1 exit status

请问是什么原因啊，我不知道哪里错了，请帮助

试试 调用instance里 写成  Temp::instance

if (!instance)
                instance = new Temp();
        return instance;
}

新人学习，能不能请楼主用文字注明下，每一段程序的意思，谢谢。

Temp *Temp::instance=NULL; 类外初始化。

{
        private:
                static Temp *instance;
};

类定义中的instance只是一个声明，对于静态成员变量，需要在类定义外单独定义并初始化该成员
Temp* Temp::instance = NULL;

楼上回答得很清楚了