Solved

Bitwise And Operation

Posted on 1998-02-02
2
341 Views
Last Modified: 2012-06-21
I am confused on Bit Comparisons.  When doing a comparison of two bit values -> example

if ((nFlags & MK_LBUTTON)==MK_LBUTTON)
   cout .....

Assuming that MK_LBUTTON = 00000001 and nFlags was Unknown
If nFlags was equal to 01010101 , the if statement would be true?  or does nFlags have to 00000001?  Basically what I am asking is that when doing the comparision is it checking for only the one in the last bit or is it comparing the entire byte?  Can someone explain how this all works and what it might be useful for?

Thanks
DArrell
0
Comment
Question by:larockd
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
2 Comments
 
LVL 7

Accepted Solution

by:
faster earned 20 total points
ID: 1180080
Only when nFlag is 00000001, it will be true.

You have to understand what is the outcome for a bit AND.  For example, 01010101 & 00000001 = 00000001 and 01010101 & 00001111 = 00000101.

If what you want is the opposite, the code should be:
if ((nFlags & MK_LBUTTON) != 0)
0
 
LVL 7

Expert Comment

by:faster
ID: 1180081
Sorry, I was so dumb when I gave the answer.

 if ((nFlags & MK_LBUTTON)==MK_LBUTTON)

As long as the last bit of nFlags is 1, it will be true.  It is the same as

 if ((nFlags & MK_LBUTTON)!=0) but the latter is more common.
0

Featured Post

Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

What is C++ STL?: STL stands for Standard Template Library and is a part of standard C++ libraries. It contains many useful data structures (containers) and algorithms, which can spare you a lot of the time. Today we will look at the STL Vector. …
  Included as part of the C++ Standard Template Library (STL) is a collection of generic containers. Each of these containers serves a different purpose and has different pros and cons. It is often difficult to decide which container to use and …
The goal of the tutorial is to teach the user how to use functions in C++. The video will cover how to define functions, how to call functions and how to create functions prototypes. Microsoft Visual C++ 2010 Express will be used as a text editor an…
The viewer will learn how to user default arguments when defining functions. This method of defining functions will be contrasted with the non-default-argument of defining functions.

738 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question