Why use 0xff

Anding an integer with 0xFF leaves only the least significant byte. This is typically referred to as "masking". When doing bitwise operations, I recommend working only with unsigned types.

The danger of the second expression comes if the type of byte1 is char. In that case, some implementations can have it signed char , which will result in sign extension when evaluating. I tried it on gcc v3. EDIT2 : As requested explanation of sign extension. Sign extension is a consequence of the way C evaluates expressions. There is a rule in C called promotion rule.

C will implicitly cast all small types to int before doing the evaluation. Let's see what happens to our expression:. If char is unsigned that value is interpreted as , if it is signed it is When doing the calculation, C will extend the value to an int size 16 or 32 bits generally. This means that if the variable is unsigned and we will keep the value , the bit-pattern of that value as int will be 0xFF. The sign was extended to the size of the tempory used to do the calculation.

And thus oring the temporary will yield the wrong result. Now, we have our x value in decimal, and we want to extract the value for each parameter. As a result, we can extract the value of each parameter :. As we've seen, this operation is especially helpful when we shift right a variable and need to extract the shifted bits.

As always, the code presented in this article is available over on GitHub. Follow the Java Category. Persistence The Persistence with Spring guides. Security The Spring Security guides. Full Archive The high level overview of all the articles on the site. Eiconic Eiconic 2, 1 1 gold badge 7 7 silver badges 17 17 bronze badges.

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Upcoming Events. Featured on Meta. Now live: A fully responsive profile. Candidate changes in Moderator Election — review your ballot. Linked And that is exactly the maintenance cost that will suffer badly. Imagine, for example, what will happen if one day someone will have to change the types involved. They will not only have to change the declarations, but they will also have to locate and change all casts!

The good programming practice is to keep the code as type-agnostic as possible. Avoid mentioning specific type names in the code unless it is absolutely necessary.

Type names should be used in declarations to specify the type of the object being declared. This is where they belong, and nowhere else. Do not use explicit type names for any other purpose besides declaring new entities.

And this also means: no annoying unnecessary casts. It introduced a number of new features like auto keyword and decltype keyword, which are specifically dedicated to one and only purpose: to help you to write type-agnostic code, to avoid mentioning specific type names in your code, to help you follow the DRY principle.

And this is very good. Some people claim that repetitive references to type names help them to understand and maintain the code, since without them they "forget" what types they are working with. This is a misguided mindset. You are not supposed to constantly remember what types you are working with. You are supposed to learn to read type-agnostic code and feel comfortable with such code. It is not as difficult as it seems.

Constant repetitive mentions of type names in the code are akin to training wheels on a bicycle. You might think they are helping you, but in reality they are impeding you.

Learn to ride without training wheels. It is scary at first, but you'll quickly grow to like it. A fine argument. But an argument that fails to address the topic at hand: should a range reducing typecast be included. I guess that makes your entire post a straw man. But, I'm a big fan of proper datatypes so, jmusther , here's a snippet for you to ponder No warnings nor errors and some lovely insulating typedefs. Not even Montmorency would disapprove.