说明：  C语言笔试必考题，掌握了这几道题，保证C语言笔试战无不胜。此系本人笔试N次后总结、整理，很好用，试试就知道啦。
(C language written test will test, is in control of these questions to ensure the C language written invincible. This was written N times after I summed up, sorting, and a good use, try to know you.)