生成随机数 random value generation

下面给出了生成随机数的函数应用，但光知道怎么用，应用中还是会出问题。知道为什么可以用，知道它是怎么来得更重要。就像数学公式，理解它的原理比用它更重要。The C programming language 会讲得比较彻底一些，告诉你它是怎么来的。

the standard libary includes a portable implementation of a pseudo-random number generator and a function for initializing the seed;the former illustrate a cast:

unsigned long int next = 1;
//rand: return pseudo-random integer on 0..32767
int rand(void)
{
    next = next * 1103515245 + 12345;
    return(unsigned int)(next/65536) % 32768;
}
//srand: set seed for rand()
void srand(unsigned int seed)
{
    next = seed;
}

_____________________

_____random value generation

<stdlib>

rand()//!<generates 0 - 0xFFFF random value.

each time the value generated is different,but they appear in the same oder.

void srand( unsigned seed);　　//!<initialize the rand() generator.

long time(long *tloc);　　　　//!return current time in second,if long *tloc is not NULL, returned value is stored in it. 

uint vGenerateRandomValue(void)
{
    unsigned int uiResult;
    srand( (unsigned int)time(0) );   //generate the seeds through time for random value each excution
    uiResult = rand()%max + 1;    //1 - max   are we wanted  
    return uiResult;
}

 srand( time(NULL) );

elementArray[i] = 50-rand() % 100;   //-50 --- 49