按你这样编译的时候提示有错误
In file included from C:\DEV-C_~1\Include\windows.h:78,
                 from e:\c\4112练~1.c:2:
C:\DEV-C_~1\Include\windef.h:153: parse error before `#'
C:\DEV-C_~1\Include\windef.h:153: warning: data definition has no type or storage class
C:\DEV-C_~1\Include\windef.h:154: parse error before `#'
C:\DEV-C_~1\Include\windef.h:154: warning: data definition has no type or storage class
C:\DEV-C_~1\Include\windef.h:155: parse error before `#'
C:\DEV-C_~1\Include\windef.h:155: warning: data definition has no type or storage class
C:\DEV-C_~1\Include\windef.h:156: parse error before `#'
C:\DEV-C_~1\Include\windef.h:156: warning: data definition has no type or storage class
C:\DEV-C_~1\Include\windef.h:157: parse error before `#'
C:\DEV-C_~1\Include\windef.h:157: warning: data definition has no type or storage class
C:\DEV-C_~1\Include\windef.h:158: parse error before `#'
C:\DEV-C_~1\Include\windef.h:158: warning: data definition has no type or storage class
C:\DEV-C_~1\Include\windef.h:159: parse error before `#'
C:\DEV-C_~1\Include\windef.h:159: warning: data definition has no type or storage class
C:\DEV-C_~1\Include\windef.h:160: parse error before `#'
C:\DEV-C_~1\Include\windef.h:160: warning: data definition has no type or storage class
C:\DEV-C_~1\Include\windef.h:161: parse error before `#'
C:\DEV-C_~1\Include\windef.h:161: warning: data definition has no type or storage class
C:\DEV-C_~1\Include\windef.h:162: parse error before `#'
C:\DEV-C_~1\Include\windef.h:162: warning: data definition has no type or storage class
C:\DEV-C_~1\Include\windef.h:163: parse error before `#'
C:\DEV-C_~1\Include\windef.h:163: warning: data definition has no type or storage class
C:\DEV-C_~1\Include\windef.h:164: parse error before `*'
C:\DEV-C_~1\Include\windef.h:164: warning: data definition has no type or storage class
C:\DEV-C_~1\Include\windef.h:165: parse error before `#'
C:\DEV-C_~1\Include\windef.h:165: warning: data definition has no type or storage class
C:\DEV-C_~1\Include\windef.h:166: parse error before `#'
C:\DEV-C_~1\Include\windef.h:166: warning: data definition has no type or storage class
C:\DEV-C_~1\Include\windef.h:167: parse error before `#'
C:\DEV-C_~1\Include\windef.h:167: warning: data definition has no type or storage class
C:\DEV-C_~1\Include\windef.h:168: parse error before `HMODULE'
C:\DEV-C_~1\Include\windef.h:168: warning: data definition has no type or storage class
C:\DEV-C_~1\Include\windef.h:169: parse error before `#'
C:\DEV-C_~1\Include\windef.h:169: warning: data definition has no type or storage class
C:\DEV-C_~1\Include\windef.h:170: parse error before `#'
C:\DEV-C_~1\Include\windef.h:170: warning: data definition has no type or storage class
C:\DEV-C_~1\Include\windef.h:171: parse error before `#'
C:\DEV-C_~1\Include\windef.h:171: warning: data definition has no type or storage class
C:\DEV-C_~1\Include\windef.h:172: parse error before `#'
C:\DEV-C_~1\Include\windef.h:172: warning: data definition has no type or storage class
C:\DEV-C_~1\Include\windef.h:173: parse error before `#'
C:\DEV-C_~1\Include\windef.h:173: warning: data definition has no type or storage class
C:\DEV-C_~1\Include\windef.h:174: parse error before `#'

if((1<=x)&&(x<=20))/*   x=8，此处为假，不执行if(){}语句中的y=x;因为y是全局变量，所以y的默认值为0   */

[ 本帖最后由 laznrbfe 于 2011-10-25 22:27 编辑 ]

我用VC++6.0编译的。

多谢了哦。。就是你说的这样。哈。终于解决了。。

我的if语句写错了，应该是：if((1<=x)&&(x<=20))

不好意思刚说错了。。是10楼的帮我解决的。。他的这个输出的是对的。。

谢谢了。。你的那个思路好像也是对的。我等下去试试。不过我是用Dev-C++  编译的。可能#include<windows.h>这个不能用吧。

我好像就是 if((1<x)&&(x>=20))
这里写错了。。 if((1<x)&&(<=20))  难怪找半天找不到问题。

if条件不满足，不进入if的执行语句，直接跳过，而y没有赋值，那么输出的结果是默认值，不同的编译器产生不同的默认值，所以，结果是不可预期的。

把 printf("\n打印y:%d\n",y );放到if里去，不过“打印”这两个字最好改英文什么的。