hello4.c
[cpp] view plaincopyprint?
- main(){int i,n[]={(((1<<1)<<(1<<1)<<(1<<
- 1)<<(1<<(1>>1)))+((1<<1)<<(1<<1))), (((1
- <<1)<<(1<<1)<<(1<<1)<<(1<<1))-((1<<1)<<(
- 1<<1)<<(1<<1))+((1<<1)<<(1<<(1>>1)))+ (1
- <<(1>>1))),(((1<<1)<<(1<<1)<<(1<<1)<< (1
- <<1))-((1<<1)<<(1<<1)<<(1<<(1>>1)))- ((1
- <<1)<<(1<<(1>>1)))),(((1<<1)<<(1<<1)<<(1
- <<1)<<(1<<1))-((1<<1)<<(1<<1)<<(1<<(1>>1
- )))-((1<<1)<<(1<<(1>>1)))),(((1<<1)<< (1
- <<1)<<(1<<1)<<(1<<1))-((1<<1)<<(1<<1)<<(
- 1<<(1>>1)))-(1<<(1>>1))),(((1<<1)<<(1<<1
- )<<(1<<1))+((1<<1)<<(1<<1)<<(1<<(1>>1)))
- -((1<<1)<<(1<<(1>>1)))),((1<<1)<< (1<<1)
- <<(1<<1)),(((1<<1)<<(1<<1)<<(1<<1)<<(1<<
- 1))-((1<<1)<<(1<<1))-(1<<(1>>1))),(((1<<
- 1)<<(1<<1)<<(1<<1)<<(1<<1))-((1<<1)<< (1
- <<1)<<(1<<(1>>1)))-(1<<(1>>1))), (((1<<1
- )<<(1<<1)<<(1<<1)<<(1<<1))- ((1<<1)<< (1
- <<1)<<(1<<(1>>1)))+(1<<1)), (((1<<1)<< (
- 1<<1)<<(1<<1)<< (1<<1))-((1<<1)<< (1<<1)
- <<(1<<(1>>1)))-((1<<1) <<(1<< (1>>1)))),
- (((1<<1)<< (1<<1)<<(1<<1)<< (1<<1))- ((1
- <<1)<<(1<<1)<<(1<<1))+((1<<1)<< (1<<(1>>
- 1)))), (((1<<1)<<(1<<1) <<(1<<1))+(1<<(1
- >>1))),(((1<<1)<<(1<<1))+((1<<1)<< (1<<(
- 1>>1))) + (1<< (1>>1)))}; for(i=(1>>1);i
- <(((1<<1) <<(1<<1))+((1 <<1)<< (1<<(1>>1
- ))) + (1<<1)); i++) printf("%c",n[i]); }
这段代码看上去比较长比较乱，其实涉及的主要就是C语言位运算中的位移运算：
<<——左移，>>——右移。一般地，左移以为代表乘以2，左移2位代表乘以4；右移一位相当于除2，右移2位代表除4；
上面代码中，主要就是通过位移，依次为整型数组int n[]赋值，分别对应的是“Hello, world!"中各字符的ASCII码值。这个可以自行计算验证。然后用%c格式化输出，将整型转化为ASCII码中对应的字符。
C语言位运算中还涉及到位逻辑运算：
1.单目运算符：~（取反）
2.双目运算:&(按位与) 、 |（按位或）、 ^（按位异或）
hello5.c
[cpp] view plaincopyprint?
- #include<stdio.h>
- #define __(a) goto a;
- #define ___(a) putchar(a);
- #define _(a,b) ___(a) __(b);
- main()
- { _:__(t)a:_(‘r‘,g)b:_(‘$‘,p)
- c:_(‘l‘,f)d:_(‘ ‘,s)e:_(‘a‘,s)
- f:_(‘o‘,q)g:_(‘l‘,h)h:_(‘d‘,n)
- i:_(‘e‘,w)j:_(‘e‘,x)k:_(‘\n‘,z)
- l:_(‘H‘,l)m:_(‘X‘,i)n:_(‘!‘,k)
- o:_(‘z‘,q)p:_(‘q‘,b)q:_(‘,‘,d)
- r:_(‘i‘,l)s:_(‘w‘,v)t:_(‘H‘,j)
- u:_(‘a‘,a)v:_(‘o‘,a)w:_(‘)‘,k)
- x:_(‘l‘,c)y:_(‘\t‘,g)z:___(0x0)}
这段代码看上去排列比较整齐，但语法比较奇怪。仔细看看，你会发现涉及的主要就两个内容：goto语句的使用以及宏定义的使用。
所有冒号左边的都是语句标号。如mian函数里面的第一句翻译过来为_:goto t;执行这个语句后跳转到语句标号为t的语句，即t:(‘H‘,j)，完成所有的宏替换，代码转换为：
[cpp] view plaincopyprint?
- main()
- {
- _:goto t;
- a:putchar(‘r‘); goto g;
- b:putchar(‘$‘); goto p;
- c:putchar(‘l‘); goto f;
- d:putchar(‘ ‘); goto s;
- e:putchar(‘a‘); goto s;
- f:putchar(‘o‘); goto q;
- g:putchar(‘l‘); goto h;
- h:putchar(‘d‘); goto n;
- i:putchar(‘e‘); goto w;
- j:putchar(‘e‘); goto x;
- k:putchar(‘\n‘); goto z;
- l:putchar(‘H‘); goto l;
- m:putchar(‘X‘); goto i;
- n:putchar(‘!‘); goto k;
- o:putchar(‘z‘); goto q;
- p:putchar(‘q‘); goto b;
- q:putchar(‘,‘); goto d;
- r:putchar(‘i‘); goto l;
- s:putchar(‘w‘); goto v;
- t:putchar(‘H‘); goto j;
- u:putchar(‘a‘); goto a;
- v:putchar(‘o‘); goto a;
- w:putchar(‘)‘); goto k;
- x:putchar(‘l‘); goto c;
- y:putchar(‘\t‘); goto g;
- z:putchar(0x0);
- }
语句间的跳转顺序为：
_ >>t>>j>>x>>c>>f>>q>>d>>s>>v>>a>>g>>h>>n>>k>>z
hello6.cpp（注意本程序只能被C++编译器编译)
#include <stdio.h>
#define _(_) putchar(_);
int main(void){int i = 0;_(
++++++++++++++++++++++++++++
++++++++++++++++++++++++++++
++++++++++++++++++++++++++++
++++++++++++++++++++++++++++
++++++++++++++++++++++++++++
++++i)_(++++++++++++++++++++
++++++++++++++++++++++++++++
++++++++++i)_(++++++++++++++
i)_(--++i)_(++++++i)_(------
----------------------------
----------------------------
----------------------------
----------------------------
----------------i)_(--------
----------------i)_(++++++++
++++++++++++++++++++++++++++
++++++++++++++++++++++++++++
++++++++++++++++++++++++++++
++++++++++++++++++++++++++++
++++++++++++++++++++++++++++
++++++++++++++++++++++++++i)
_(----------------i)_(++++++
i)_(------------i)_(--------
--------i)_(----------------
----------------------------
----------------------------
----------------------------
----------------------------
------i)_(------------------
----------------------------
i)return i;}
这段代码看上去比较炫，其实是很无聊的，通过自增，自减运算符为 i 赋值，而这些值都是"Hello, world!"字符串中对应字符的ASCII码值，用putchar(c)输出。
写到这儿，六个变态的C语言Hello world程序全部介绍完毕。咋一眼看上去确实不知所云，在我不说明的情况下你鞥一眼辨别程序要输出的是什么吗？我想还是有点困难的。当然 我们不提倡C语言混乱代码，写出一些让人摸不着头脑礼节性差的代码，但通过分析这些混乱的代码，明白其中的道理所在，通过分析，层层解开混乱代码后的神秘面纱，我想这应该也算是学习C语言的乐趣之所在。写出这样的混乱代码，确实是件很酷的事情！