似乎没有人提到定点数学。

(是的，我老了，好吗?)

我一直假设按位操作是相当简单的操作，所以当运行时间至关重要时，通过bitset实现的解决方案可以通过恒定的数量提高运行时间，这取决于算法。

Bit fields (flags) They're the most efficient way of representing something whose state is defined by several "yes or no" properties. ACLs are a good example; if you have let's say 4 discrete permissions (read, write, execute, change policy), it's better to store this in 1 byte rather than waste 4. These can be mapped to enumeration types in many languages for added convenience. Communication over ports/sockets Always involves checksums, parity, stop bits, flow control algorithms, and so on, which usually depend on the logic values of individual bytes as opposed to numeric values, since the medium may only be capable of transmitting one bit at a time. Compression, Encryption Both of these are heavily dependent on bitwise algorithms. Look at the deflate algorithm for an example - everything is in bits, not bytes. Finite State Machines I'm speaking primarily of the kind embedded in some piece of hardware, although they can be found in software too. These are combinatorial in nature - they might literally be getting "compiled" down to a bunch of logic gates, so they have to be expressed as AND, OR, NOT, etc. Graphics There's hardly enough space here to get into every area where these operators are used in graphics programming. XOR (or ^) is particularly interesting here because applying the same input a second time will undo the first. Older GUIs used to rely on this for selection highlighting and other overlays, in order to eliminate the need for costly redraws. They're still useful in slow graphics protocols (i.e. remote desktop).

这些只是我最先想到的几个例子——这不是一个详尽的清单。

低级编程就是一个很好的例子。例如，你可能需要写一个特定的位到内存映射寄存器，以使某些硬件做你想要它做的事情:

volatile uint32_t *register = (volatile uint32_t *)0x87000000;
uint32_t          value;
uint32_t          set_bit   = 0x00010000;
uint32_t          clear_bit = 0x00001000;

value = *register;            // get current value from the register
value = value & ~clear_bit;   // clear a bit
value = value | set_bit;      // set a bit
*register = value;            // write it back to the register

同样，htonl()和htons()是使用&和|操作符实现的(在字节顺序不匹配网络顺序的机器上):

#define htons(a) ((((a) & 0xff00) >> 8) | \
                  (((a) & 0x00ff) << 8))

#define htonl(a) ((((a) & 0xff000000) >> 24) | \
                  (((a) & 0x00ff0000) >>  8) | \
                  (((a) & 0x0000ff00) <<  8) | \
                  (((a) & 0x000000ff) << 24))

如果你想计算你的数字mod(%) 2的某次方，你可以使用yourNumber & 2^N-1，在这种情况下，它与yourNumber % 2^N相同。

number % 16 = number & 15;
number % 128 = number & 127;

这可能只是作为模数运算的一种替代品有用，它的红利很大，是2^N。但即便如此，在我在。net 2.0上的测试中，它相对于模运算的速度提升也可以忽略不计。我怀疑现代编译器已经执行了这样的优化。有人知道更多吗?

通常位运算比乘除运算快。所以如果你需要用一个变量x乘以9，你会用x<<3 + x这将比x*9快几个周期。如果此代码位于ISR中，则可以节省响应时间。

类似地，如果您想使用数组作为循环队列，那么使用逐位操作来处理环绕检查会更快(也更优雅)。(你的数组大小应该是2的幂)。例如:，你可以使用tail = ((tail & MASK) +1)而不是tail = ((tail +1) < size) ?尾+1:0，如果你想插入/删除。

另外，如果您想要一个错误标志将多个错误代码保存在一起，则每个位可以保存一个单独的值。您可以与它与每个单独的错误代码作为检查。这用于Unix错误代码。

此外，n位位图可以是一个非常酷而紧凑的数据结构。如果要分配一个大小为n的资源池，我们可以使用n位表示当前状态。