# Assembler level and C level types

In order to provide intuitive yet powerful interface to types IDA introduces two kinds of types:

```
  - Assembler level types
  - C level types
```

Assembler level types are the ones defined by the user using the [Struct](/8.4/user-guide/user-interface/menu-bar/view/open-subviews.md#structures-window) or [Enum](/8.4/user-guide/user-interface/menu-bar/view/open-subviews.md#enums-window) views.

Since the user has to specify manually the member offset and other attributes, IDA considers the member offsets to be fixed for them and never shifts members of such types. If a member of struct becomes too big and does not fit the struct anymore, IDA will delete it.

The types defined in the [Local types](/8.4/user-guide/user-interface/menu-bar/view/open-subviews.md#local-types-window) window are considered as C level types. For them IDA automatically calculates the member offsets and if necessary may shift members and change the total struct size.

The user may change the type level by simply editing the type from the appropriate window. For example, if a C level type is edited from the [Struct](/8.4/user-guide/user-interface/menu-bar/view/open-subviews.md#structures-window) view, IDA will consider such a type as an Assembler level type in the future.

```
 In the struct/enum view:
  Assembler level types are displayed using regular colors.
  C level types are displayed in gray, as if they are disabled (but they are not).

 In the local types view:
  C level types are displayed using regular colors.
  Assembler level types are displayed in gray, as if they are disabled (but they are not).
```


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