一个数x是2的幂吗?(例如，在计数器递增的算法中很有用，并且一个操作只执行对数次)

(x & (x - 1)) == 0

整数x的最高位是哪位?(例如，这可以用来找出比x大的2的最小次幂)

x |= (x >>  1);
x |= (x >>  2);
x |= (x >>  4);
x |= (x >>  8);
x |= (x >> 16);
return x - (x >>> 1); // ">>>" is unsigned right shift

整数x的最小1位是哪一位?(帮助找出能被2整除的次数。)

x & -x

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。

在当今现代语言的抽象世界里，没有太多。File IO是一个容易想到的方法，尽管它是在已经实现的东西上执行按位操作，而不是实现使用按位操作的东西。尽管如此，作为一个简单的例子，这段代码演示了在c#中删除文件上的只读属性(这样它就可以与指定FileMode.Create的新FileStream一起使用):

//Hidden files posses some extra attibutes that make the FileStream throw an exception
//even with FileMode.Create (if exists -> overwrite) so delete it and don't worry about it!
if(File.Exists(targetName))
{
    FileAttributes attributes = File.GetAttributes(targetName);

    if ((attributes & FileAttributes.ReadOnly) == FileAttributes.ReadOnly)
        File.SetAttributes(targetName, attributes & (~FileAttributes.ReadOnly));

    File.Delete(targetName);
}

As far as custom implementations, here's a recent example: I created a "message center" for sending secure messages from one installation of our distributed application to another. Basically, it's analogous to email, complete with Inbox, Outbox, Sent, etc, but it also has guaranteed delivery with read receipts, so there are additional subfolders beyond "inbox" and "sent." What this amounted to was a requirement for me to define generically what's "in the inbox" or what's "in the sent folder". Of the sent folder, I need to know what's read and what's unread. Of what's unread, I need to know what's received and what's not received. I use this information to build a dynamic where clause which filters a local datasource and displays the appropriate information.

下面是枚举是如何组合在一起的:

    public enum MemoView :int
    {
        InboundMemos = 1,                   //     0000 0001
        InboundMemosForMyOrders = 3,        //     0000 0011
        SentMemosAll = 16,                  //     0001 0000
        SentMemosNotReceived = 48,          //     0011
        SentMemosReceivedNotRead = 80,      //     0101
        SentMemosRead = 144,                //     1001
        Outbox = 272,                       //0001 0001 0000
        OutBoxErrors = 784                  //0011 0001 0000
    }

你明白这是怎么回事了吗?通过与“收件箱”枚举值InboundMemos加上(&)，我知道InboundMemosForMyOrders在收件箱中。

下面是该方法的简化版本，它构建并返回为当前选择的文件夹定义视图的过滤器:

    private string GetFilterForView(MemoView view, DefaultableBoolean readOnly)
    {
        string filter = string.Empty;
        if((view & MemoView.InboundMemos) == MemoView.InboundMemos)
        {
            filter = "<inbox filter conditions>";

            if((view & MemoView.InboundMemosForMyOrders) == MemoView.InboundMemosForMyOrders)
            {
                filter += "<my memo filter conditions>";
            }
        }
        else if((view & MemoView.SentMemosAll) == MemoView.SentMemosAll)
        {
            //all sent items have originating system = to local
            filter = "<memos leaving current system>";

            if((view & MemoView.Outbox) == MemoView.Outbox)
            {
                ...
            }
            else
            {
                //sent sub folders
                filter += "<all sent items>";

                if((view & MemoView.SentMemosNotReceived) == MemoView.SentMemosNotReceived)
                {
                    if((view & MemoView.SentMemosReceivedNotRead) == MemoView.SentMemosReceivedNotRead)
                    {
                        filter += "<not received and not read conditions>";
                    }
                    else
                        filter += "<received and not read conditions>";
                }
            }
        }

        return filter;
    }

非常简单，但在抽象级别上是一个整洁的实现，通常不需要按位操作。

不久前，我在维基上写了一篇小文章，展示了一个二进制的作者/读者。它在位级上工作，并展示了如何使用位操作符来打包数据。这可能是一个“现实世界”的例子，因为它在游戏中也有应用。

数据库世界中的另一个真实应用程序是MySQL，它的数据类型是SET。

位操作符由DBMS存储SET数据类型。设置可以节省空间。

Element    SET Value    Decimal Value
Travel      00000001    1
Sports      00000010    2
Dancing    00000100    4
Fine Dining   00001000  8

我曾在一些游戏开发书籍中看到它是一种更有效的乘除方法。

2 << 3 == 2 * 8 
32 >> 4 == 32 / 16