> ## Documentation Index
> Fetch the complete documentation index at: https://docs.abbyy.com/llms.txt
> Use this file to discover all available pages before exploring further.

# ABBYY FineReader Engine 12 and 10 Compatibility

> Compatibility changes between ABBYY FineReader Engine 12 and 10: long → int, new __int64/Handle type, header and library differences, and recompilation requirements.

ABBYY FineReader Engine 12 is not binary compatible with ABBYY FineReader Engine 10. Applications that were compiled using ABBYY FineReader Engine 10 should be recompiled using ABBYY FineReader Engine 12 headers and library. Some changes of the source code may be necessary because of the ABBYY FineReader Engine API improvements.

Main changes:

* long data type has been replaced with int data type in all properties and methods that used it. This change has been made to avoid ambiguity: long data type could be 64-bit or 32-bit in different operating systems, while int data type is always 32-bit.

* In addition to this, \_\_int64 data type has been introduced. In Windows, it has been introduced with a new [Handle](/fine-reader/engine/api-reference/supplementary-objects-and-methods/handle) object that manages memory allocation and allows you to avoid memory leaks while working with resources in memory. It also provides a method for conversion to \_\_int64.

* In Windows, the parameters type of the [SaveToMemory](/fine-reader/engine/api-reference/supplementary-objects-and-methods/savetomemory-method) and [LoadFromMemory](/fine-reader/engine/api-reference/supplementary-objects-and-methods/loadfrommemory-method) methods provided by many objects has been changed:

* Now the handle to the memory buffer is returned by the [SaveToMemory](/fine-reader/engine/api-reference/supplementary-objects-and-methods/savetomemory-method) method as the [Handle](/fine-reader/engine/api-reference/supplementary-objects-and-methods/handle) object.

* The handle to the memory buffer is passed to the [LoadFromMemory](/fine-reader/engine/api-reference/supplementary-objects-and-methods/loadfrommemory-method) method as [\_\_int64](/fine-reader/engine/guided-tour/advanced-techniques/programming-aspects/working-with-properties).

* The Classification API has been completely replaced, using new improved algorithms and providing built-in cross-validation techniques.

* The [Engine](/fine-reader/engine/api-reference/engine-object-iengine-interface) object must now be loaded by [InitializeEngine](/fine-reader/engine/api-reference/functions/initializeengine-function) function. The GetEngineObject and GetEngineObjectEx functions for Engine loading are removed from ABBYY FineReader Engine.

For the detailed description of other changes in API see corresponding section:

* [Business cards API](/fine-reader/engine/specifications/backward-compatibility-issues/version-10/business-cards-api)
* [Functions](/fine-reader/engine/specifications/backward-compatibility-issues/version-10/functions)
* [Engine Object](/fine-reader/engine/specifications/backward-compatibility-issues/version-10/engine-object)
  * [Engine for Java](/fine-reader/engine/specifications/backward-compatibility-issues/version-10/engine-object/engine-for-java) (Linux and Windows)
* [Engine Loaders](/fine-reader/engine/specifications/backward-compatibility-issues/version-10/engine-loaders) (Windows)
* [Image-Related Objects](/fine-reader/engine/specifications/backward-compatibility-issues/version-10/image-related-objects)
* [Layout-Related Objects](/fine-reader/engine/specifications/backward-compatibility-issues/version-10/layout-related-objects)
* [Language-Related Objects](/fine-reader/engine/specifications/backward-compatibility-issues/version-10/language-related-objects)
* [Text-Related Objects](/fine-reader/engine/specifications/backward-compatibility-issues/version-10/text-related-objects)
* [Document-Related Objects](/fine-reader/engine/specifications/backward-compatibility-issues/version-10/document-related-objects)
* [BatchProcessor Object and Related Interfaces](/fine-reader/engine/specifications/backward-compatibility-issues/version-10/batch-processor) (Linux and Windows)
* [Mechanism Objects](/fine-reader/engine/specifications/backward-compatibility-issues/version-10/mechanism-objects)
* [Parameter Objects](/fine-reader/engine/specifications/backward-compatibility-issues/version-10/parameter-objects)
* [License-Related Objects](/fine-reader/engine/specifications/backward-compatibility-issues/version-10/license-related-objects)
* [Supplementary Objects](/fine-reader/engine/specifications/backward-compatibility-issues/version-10/supplementary-objects)
* [Visual Components](/fine-reader/engine/specifications/backward-compatibility-issues/version-10/visual-components) (Windows)