What is the difference between “int” and “uint” / “long” and “ulong”?

Question

I know about int and long (32-bit and 64-bit numbers), but what are uint and ulong?

Solution 1

The primitive data types prefixed with "u" are unsigned versions with the same bit sizes. Effectively, this means they cannot store negative numbers, but on the other hand they can store positive numbers twice as large as their signed counterparts. The signed counterparts do not have "u" prefixed.

The limits for int (32 bit) are:

int: –2147483648 to 2147483647 
uint: 0 to 4294967295 

And for long (64 bit):

long: -9223372036854775808 to 9223372036854775807
ulong: 0 to 18446744073709551615

Solution 2

uint and ulong are the unsigned versions of int and long. That means they can't be negative. Instead they have a larger maximum value.

Type    Min                           Max                           CLS-compliant
int     -2,147,483,648                2,147,483,647                 Yes
uint    0                             4,294,967,295                 No
long    –9,223,372,036,854,775,808    9,223,372,036,854,775,807     Yes
ulong   0                             18,446,744,073,709,551,615    No

To write a literal unsigned int in your source code you can use the suffix u or U for example 123U.

You should not use uint and ulong in your public interface if you wish to be CLS-Compliant.

Read the documentation for more information:

• int
• uint
• long
• ulong

By the way, there is also short and ushort and byte and sbyte.

Solution 3

The difference is that the uint and ulong are unsigned data types, meaning the range is different: They do not accept negative values:

int range: -2,147,483,648 to 2,147,483,647
uint range: 0 to 4,294,967,295

long range: –9,223,372,036,854,775,808 to 9,223,372,036,854,775,807
ulong range: 0 to 18,446,744,073,709,551,615

Solution 4

u means unsigned, so ulong is a large number without sign. You can store a bigger value in ulong than long, but no negative numbers allowed.

A long value is stored in 64-bit,with its first digit to show if it's a positive/negative number. while ulong is also 64-bit, with all 64 bit to store the number. so the maximum of ulong is 2(64)-1, while long is 2(63)-1.

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Comments

[Jaco Pretorius]

This is quite fun to work out by hand. A 32-bit signed variable uses 1 bit for the sign (positive or negative) so can store values between -2^31 and +2^31 - 1

[Isak Savo]

This is interesting - what do you mean about CLS compliant? The link goes to the MSDN documentation for int. If by "CLS" you mean C# language spec then I don't understand - the spec clearly describes both uint and ulong (section 1.3)

[Mark Byers]

@Isak Savo: It is important to be CLS-compliant if you are writing interface that could be used by other .NET languages than C#.

[Roman Starkov]

Curious that you mention short and ushort but leave out byte and sbyte :)

[Arun Prasad]

when comparing int and uint for usage, which one is feasible?

[Darkgaze]

What's the c++ equivalent?

[C4d]

@JacoPretorius Thats wrong. 8 bit int has a range from –128 to 127. The 9th bit represents 256. So with 8 bits you can represent all values up to 255 (9th val - 1). The range from -128 to 127 has a length of exactly 255. So there is no bit that holds the sign. All values up to 127 are positive. Values above get displayed negative. 255 would be -1. 254 would be -2 and so one way down to 128.

[db2]

I think it's also worth noting that specifically for int vs uint, the unsigned integer is not CLS-compliant, and it's recommended to use int as often as possible.