C++ 随机数，根据时间生成随机数，Srand 与Rand 产生随机数

// srandTest.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream>   //输入输出用到的头文件
#include <time.h>     //time 用到的头文件
#include <Windows.h>  //Sleep 用到的头文件
using namespace	std;

void testRand(void); //函数原型
void testSrand(void);//函数原型
int _tmain(int argc, _TCHAR* argv[])
{
cout << "*************testRand**************" << endl;
testRand();
cout << "\r\n*************testSrand**************" << endl;
testSrand();
cin.get();//捕获输入种子后的ENTER键
cin.get();
return 0;
}
void testRand()
{
int cinNum, coutNum;
for (int i = 0; i < 5; ++i)
{
cout << "please enter a number as seed:" << endl;
cin >> cinNum;
srand(cinNum); //将输入的数字作为种子
for (int i = 0; i < 5; ++i)
{
coutNum = rand() % 100; //产生1-100以内的随机数
cout << "random number:" << coutNum << endl;
}
}
}
void testSrand()
{
int coutNum;
for (int i = 0; i < 5; ++i)
{
cout << "generate seed by system time" << endl;
Sleep(1478); //设置程序休眠时长，若不设置，则由于计算机处理速度过快，系统时间相同，种子相同
srand((unsigned)time(NULL));

for (int i = 0; i < 5; ++i)
{
coutNum = rand() % 100;
cout << "random number:" << coutNum << endl;
}
}
}