# Aliases of built-in types
# Built-In Types Table
The following table shows the keywords for built-in C# types, which are aliases of predefined types in the System namespaces.
| C# Type | .NET Framework Type |
|---|---|
| bool | System.Boolean |
| byte | System.Byte |
| sbyte | System.SByte |
| char | System.Char |
| decimal | System.Decimal |
| double | System.Double |
| float | System.Single |
| int | System.Int32 |
| uint | System.UInt32 |
| long | System.Int64 |
| ulong | System.UInt64 |
| object | System.Object |
| short | System.Int16 |
| ushort | System.UInt16 |
| string | System.String |
The C# type keywords and their aliases are interchangeable. For example, you can declare an integer variable by using either of the following declarations:
int number = 123;
System.Int32 number = 123;