At the core of VAST Platform (VA Smalltalk) is a development environment designed to support the easy creation of software applications on multiple platforms. It provides a platform-independent application program interface (API) based on industry standards.

Comprising nine subsystems, VAST Base encompasses the functionality required by most Smalltalk applications. Applications programmed entirely in accordance with the VA Smalltalk interface specification run without modification on all supported platforms, yet adopt the native look and feel of the particular platform. This enables applications to be produced from a single code base across multiple platforms, while still providing a high degree of platform integration.

VAST Base directly utilizes the native functionality provided by each platform. It emulates API functionality not directly supported by a particular platform in order to support a complete and consistent interface across all supported platforms. As part of the implementation of VAST Base, access to platform-specific functionality is also provided.

VAST Base does not include visual programming paradigm. This paradigm, also known as composition from VAST parts, is supported in the full VAST Platform.

Throughout the remainder of this book, VAST Base is referred to as VA Smalltalk or VAST for simplicity unless it is important to note the exclusion of VAST parts.