Bitwise 運算子

1. bitwise 運算是一個位元一個位元進行運算，運算方式有 and, or, exclusive or,complement, left shift, right shift：
   

   p	q	p&q	p|q	p^q
   0	0	0	0	0
   0	1	0	1	1
   1	1	1	1	0
   1	0	0	1	1

2. 實例：若 A=60(00111100) B=13(00001101)
   

   運算子	描述	結果
   &	Binary AND	(A&B)=12 (00001100)
   |	Binary OR	(A|B)=61 (00111101)
   ^	Binary XOR	(A^B)=49 (00110001)
   ~	Binary Ones complement	(~A)=-61 (11000011)
   <<	Binary left shift	A<<2=240 (11110000)
   >>	Binary right shift	A>>2=15 (00001111)

3. 程式實例：A=60(00111100) B=13(00001101)

   [dywang@deyu zzz]$ vim op-bw1.c 
   [dywang@deyu zzz]$ cat op-bw1.c 
   #include <stdio.h>
   
   int main() {
   	unsigned int a = 60; /* 60 = 0011 1100 */
   	unsigned int b = 13; /* 13 = 0000 1101 */
   	int c = 0;
   
   	c = a & b;       /* 12 = 0000 1100 */
   	printf("00111100 & 00001101 = %d (00001100)\n", c );
   
   	c = a | b;       /* 61 = 0011 1101 */
   	printf("00111100 | 00001101 = %d (00111101)\n", c );
   
   	c = a ^ b;       /* 49 = 0011 0001 */
   	printf("00111100 ^ 00001101 = %d (00110001)\n", c );
   
   	c = ~a;          /*-61 = 1100 0011 */
   	printf("~00111100 = %d (11000011)\n", c );
   
   	c = a << 2;     /* 240 = 1111 0000 */
   	printf("00111100 << 2 = %d (11110000)\n", c );
   
   	c = a >> 2;     /* 15 = 0000 1111 */
   	printf("00111100 >> 2 = %d (00001111)\n", c );
   }
   

4. 編譯成功

   [dywang@deyu zzz]$ gcc -o op-bw1 op-bw1.c
   

5. 執行結果

   [dywang@deyu zzz]$ ./op-bw1 
   00111100 & 00001101 = 12 (00001100)
   00111100 | 00001101 = 61 (00111101)
   00111100 ^ 00001101 = 49 (00110001)
   ~00111100 = -61 (11000011)
   00111100 << 2 = 240 (11110000)
   00111100 >> 2 = 15 (00001111)
   

6. 用 bc 以二進位表示驗證。

   [dywang@deyu zzz]$ echo 'obase=2;15' | bc
   1111
   [dywang@deyu zzz]$ echo 'obase=2;240' | bc
   11110000