函数名: brk 
 功  能: 改变数据段空间分配 
 用  法: #include <alloc.h>
         int brk(void *endds); 
 程序例: 
#include <stdio.h> 
 #include <alloc.h> 
int main(void) 
 { 
    char *ptr; 
   printf("Changing allocation with brk()\n"); 
    ptr = malloc(1); 
    printf("Before brk() call: %lu bytes free\n", coreleft()); 
    brk(ptr+1000); 
    printf(" After brk() call: %lu bytes free\n", coreleft()); 
    return 0; 
 }