# Overview
## IDA type system fundamentals
The IDA type system is based on familiar C-like constructs such as:
* **Structures**: Aggregate data types that group multiple members.
* **Unions**: Allow overlapping the same memory with different data types.
* **Enums**: Provide named integer constants.
IDA ships with [type libraries](/core/types.md#type-libraries) out-of-the-box, but you can define custom types in the [Local Types window](/core/types.md#type-management-essentials-local-types-view).
## Type definitions sources
* Built-in or custom [type libraries](/core/types.md#type-libraries)(.til files)
* Custom types
* Debug information (e.g., PDB or DWARF)
## Type libraries
IDA ships with type libraries for popular platforms and operating systems. They provide high-level, predefined data types that can be used in your analysis. You can view a list of currently loaded type libraries in the **Type Libraries** window (**View → Open subviews → Type Libraries**, or Shift+F11)
{% hint style="info" %}
**Relation between Local Types and Type Libraries**:
In IDA, **Local Types** are custom or imported type definitions specific to your current project, while **Type Libraries** provide pre-defined types for common platforms and architectures. Types in the **Type Libraries**, once referenced, are copied into the IDB and appear under the **Local Types** window.
{% endhint %}
Type library may contain:
* function prototypes
* typedefs
* structure and enum definitions
**See also**
* [TILIB](/core/types/how-tos/creating-type-libraries/tilib.md) and [IDAClang](/core/types/how-tos/creating-type-libraries/idaclang_tutorial.md) tutorials on creating custom type libraries
* Type libraries in[ Igor's tip of the week](https://hex-rays.com/blog/igors-tip-of-the-week-60-type-libraries/) blog post
## Local Types view
The Local Types view provides a centralized hub for managing and customizing type definitions directly within the IDA UI. To access this view, navigate to **View → Open subviews → Local Types** or press Shift+F1 keys.
The Local Types view allows you to:
* Create custom structures, unions, and enums
* Modify and delete existing types
See also:
* Refer to the [Working with Types](/core/types/how-tos/working-with-types.md) for a practical step-by-step tutorial covering the essentials of type management
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