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

Question

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

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.

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

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.