---
description: "Learn more about: default (C++)"
title: "default  (C++ COM Attribute)"
ms.date: "10/02/2018"
f1_keywords: ["vc-attr.default"]
helpviewer_keywords: ["default attribute", "attributes [C#], default attribute", "defaults, default attribute"]
ms.assetid: 0cdca716-1ba8-46d7-9399-167e55492870
---
# default (C++)

Indicates that the custom or dispinterface defined within a coclass represents the default programmability interface.

## Syntax

```cpp
[ default(interface1, interface2) ]
```

### Parameters

*interface1*<br/>
The default interface that will be made available to scripting environments that create an object based on the class defined with the **`default`** attribute.

If no default interface is specified, the first occurrence of a nonsource interface is used as the default.

*interface2*<br/>
(Optional) The default source interface. You must also specify this interface with the [source](source-cpp.md) attribute.

If no default source interface is specified, the first source interface is used as the default.

## Remarks

The **`default`** C++ attribute has the same functionality as the [default](/windows/win32/Midl/default) MIDL attribute. The **`default`** attribute is also used with the [case](case-cpp.md) attribute.

## Example

The following code shows how **`default`** is used on the definition of a coclass to specify `ICustomDispatch` as the default programmability interface:

```cpp
// cpp_attr_ref_default.cpp
// compile with: /LD
#include "windows.h"
[module(name="MyLibrary")];

[object, uuid("9E66A290-4365-11D2-A997-00C04FA37DDB")]
__interface ICustom {
   HRESULT Custom([in] long l, [out, retval] long *pLong);
};

[dual, uuid("9E66A291-4365-11D2-A997-00C04FA37DDB")]
__interface IDual {
   HRESULT Dual([in] long l, [out, retval] long *pLong);
};

[object, uuid("9E66A293-4365-11D2-A997-00C04FA37DDB")]
__interface ICustomDispatch : public IDispatch {
   HRESULT Dispatch([in] long l, [out, retval] long *pLong);
};

[   coclass, default(ICustomDispatch), source(IDual), uuid("9E66A294-4365-11D2-A997-00C04FA37DDB")
]
class CClass : public ICustom, public IDual, public ICustomDispatch {
   HRESULT Custom(long l, long *pLong) { return(S_OK); }
   HRESULT Dual(long l, long *pLong) { return(S_OK); }
   HRESULT Dispatch(long l, long *pLong) { return(S_OK); }
};

int main() {
#if 0 // Can't instantiate without implementations of IUnknown/IDispatch
   CClass *pClass = new CClass;

   long llong;

   pClass->custom(1, &llong);
   pClass->dual(1, &llong);
   pClass->dispinterface(1, &llong);
   pClass->dispatch(1, &llong);

   delete pClass;
#endif
   return(0);
}
```

The [source](source-cpp.md) attribute also has an example of how to use **`default`**.

## Requirements

| Attribute context | Value |
|-|-|
|**Applies to**|**`class`**, **`struct`**, data member|
|**Repeatable**|No|
|**Required attributes**|**coclass** (when applied to **`class`** or **`struct`**)|
|**Invalid attributes**|None|

For more information, see [Attribute Contexts](cpp-attributes-com-net.md#contexts).

## See also

[IDL Attributes](idl-attributes.md)<br/>
[Class Attributes](class-attributes.md)<br/>
[coclass](coclass.md)