Why Should I Use Int Instead of a Byte or Short in C#

Why should I use int instead of a byte or short in C#

Performance-wise, an int is faster in almost all cases. The CPU is designed to work efficiently with 32-bit values.

Shorter values are complicated to deal with. To read a single byte, say, the CPU has to read the 32-bit block that contains it, and then mask out the upper 24 bits.

To write a byte, it has to read the destination 32-bit block, overwrite the lower 8 bits with the desired byte value, and write the entire 32-bit block back again.

Space-wise, of course, you save a few bytes by using smaller datatypes. So if you're building a table with a few million rows, then shorter datatypes may be worth considering. (And the same might be good reason why you should use smaller datatypes in your database)

And correctness-wise, an int doesn't overflow easily. What if you think your value is going to fit within a byte, and then at some point in the future some harmless-looking change to the code means larger values get stored into it?

Those are some of the reasons why int should be your default datatype for all integral data. Only use byte if you actually want to store machine bytes. Only use shorts if you're dealing with a file format or protocol or similar that actually specifies 16-bit integer values. If you're just dealing with integers in general, make them ints.

Byte vs Short vs Int (Along With The Unsigned Variation) In C#?

It depends more on the processor than on the language. An 8-bit microcontroller will almost certainly be able to access an 8-bit char faster than a 32-bit int.

Being aware of this limitation allows algorithm designers to plan accordingly: One of the reasons why Rijndael won the AES competition is because the designers had planned for making 8-bit versions as fast as possible, in addition to caring about execution speed on 32-bit or larger processors.

But for 32-bit and 64-bit microprocessors, data alignment and bulk data access is key: int accesses are frequently much faster than char accesses, and long long (64 bit) may be faster still for some systems. (But the 64-bit operations on a 32-bit machine are much slower, so using 64-bit datatypes makes most sense when the data actually makes more sense in 64 bits.)

Should I use byte or int?

Usually yes, a 32 bit integer will perform slightly better because it is already properly aligned for native CPU instructions. You should only use a smaller sized numeric type when you actually need to store something of that size.

Why does the Java API use int instead of short or byte?

Some of the reasons have already been pointed out. For example, the fact that "...(Almost) All operations on byte, short will promote these primitives to int". However, the obvious next question would be: WHY are these types promoted to int?

So to go one level deeper: The answer may simply be related to the Java Virtual Machine Instruction Set. As summarized in the Table in the Java Virtual Machine Specification, all integral arithmetic operations, like adding, dividing and others, are only available for the type int and the type long, and not for the smaller types.

_{(An aside: The smaller types (byte and short) are basically only intended for arrays. An array like new byte[1000] will take 1000 bytes, and an array like new int[1000] will take 4000 bytes)}

Now, of course, one could say that "...the obvious next question would be: WHY are these instructions only offered for int (and long)?".

One reason is mentioned in the JVM Spec mentioned above:

If each typed instruction supported all of the Java Virtual Machine's run-time data types, there would be more instructions than could be represented in a byte

Additionally, the Java Virtual Machine can be considered as an abstraction of a real processor. And introducing dedicated Arithmetic Logic Unit for smaller types would not be worth the effort: It would need additional transistors, but it still could only execute one addition in one clock cycle. The dominant architecture when the JVM was designed was 32bits, just right for a 32bit int. (The operations that involve a 64bit long value are implemented as a special case).

_{(Note: The last paragraph is a bit oversimplified, considering possible vectorization etc., but should give the basic idea without diving too deep into processor design topics)}

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EDIT: A short addendum, focussing on the example from the question, but in an more general sense: One could also ask whether it would not be beneficial to store fields using the smaller types. For example, one might think that memory could be saved by storing Calendar.DAY_OF_WEEK as a byte. But here, the Java Class File Format comes into play: All the Fields in a Class File occupy at least one "slot", which has the size of one int (32 bits). (The "wide" fields, double and long, occupy two slots). So explicitly declaring a field as short or byte would not save any memory either.

Does it really matter to distinct between short, int, long?

Unless you are packing large numbers of these together in some kind of structure, it will probably not affect the memory consumption at all. The best reason to use a particular integer type is compatibility with an API. Other than that, just make sure the type you pick has enough range to cover the values you need. Beyond that for simple local variables, it doesn't matter much.

c# - is SHORT data type or it is still INT?

In C#, the following things are always true:

• short == Int16
• ushort == UInt16
• int == Int32
• uint == UInt32
• long == Int64
• ulong == UInt64

Both versions are data types. All of the above are integers of various lengths and signed-ness.

The main difference between the two versions (as far as I know) is what colour they are highlighted as in Visual Studio.

Does casting a byte to an int or declaring an int carry more overhead in C#?

seems like you think its a good idea to save 3 bytes by making foo a byte. Its not, it wont make any speed or space difference and it will simply confuse readers of the code (including you), and add subtle bugs when you change the code later.

If you were storing lots of numbers and you know the were all 1 byte then yes this would save space an you should do it. But not in the trivial case you show

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