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Gregor Permalink
October 20, 2010, 18:13

I'm a web developer in PHP and JavaScript and only recently have I become interested in bitwise operations. I don't really have a need for them, but I'd like to know more about them. #1 I can see a use-case for - of course I sometimes want to know if integers are odd or even - but the rest of them I can't see why you would ever want/need to do this.

Can someone please provide some examples of why you would want to do things to the nth bit? I don't see what this actually achieves.

Comment Responses

YA mark Permalink
October 21, 2010, 13:47

How about making an amber and green LED alternately flash on your cool new widget you are building with a microcontroller?
Testing so a robotic control program will know that one of its sensors has tripped. (it has hit the wall, and maybe should reverse for a bit.)
This type of activity is usually reserved for hardware programming / embedded systems. It's what makes your keyboard work with a single chip and an embedded program to convert switch closures into a stream of characters the computer can use as input.

Gregor Permalink
October 21, 2010, 20:46

Thanks Mark. So I'm relatively safe in my ignorance of these then - until I start trying to install Linux on my toaster.

Nathan Myers Permalink
May 11, 2018, 05:06

A binary word is not just a number. It is also a set: for each possible element value, a 1 tells you it is present, a 0 it is not. A byte can represent days of a week, a 32-bit word is enough for a month. 0x6060c183, shifted and masked, identifies the weekend days in any month.

In C++ std::bitset<> wraps a lot of this stuff in less hacky garb.

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