What was the code name for Microsoft's Visual Basic 1.0?

The code name for Microsoft Visual Basic 1.0 was Thunder. The project combined a visual form-design system with Microsoft’s BASIC programming language to make Windows application development faster and more approachable.

Visual Basic grew partly from Ruby, a drag-and-drop interface builder developed by Alan Cooper and his company, Tripod. Microsoft combined that interface technology with an embedded BASIC engine associated with an abandoned database project. The resulting environment let developers place controls on forms, set properties, and attach code to events instead of writing all Windows interface plumbing manually.

Visual Basic 1.0 was released for Windows in May 1991 at the Windows World trade show in Atlanta, Georgia. Its internal heritage remained visible after launch: runtime and control names continued to use Thunder prefixes in later classic Visual Basic versions.

Thunder is sometimes confused with Ruby, but the names referred to different parts of the project. Ruby was the form-building technology, while Thunder identified the broader Visual Basic effort that became the shipped product.