说明：  　　fork和exec系列调用前后，进程在内存的“数据段”，“堆栈段”和“代码段”有什么不同？读了之后，你就会知道了，
(fork and exec calls before and after the Series, in memory of the process "of the data", "stack of" and "code of" what's the difference? After reading, you will know,)