What Was the Windows 95 Development Codename?

During the early 1990s, Microsoft embarked on an ambitious project to revolutionize personal computing by merging MS-DOS with a graphical user interface into a unified, consumer-friendly 32-bit operating system. Internally, this groundbreaking project was developed under a specific geographic moniker before its public release in August 1995. This article details the official codename used for Windows 95 during its development, the historical context behind the project, and its impact on the final product.

The Official Codename: Chicago

The primary internal codename for Windows 95 was Chicago.

Microsoft initiated the Chicago project around March 1992, immediately following the launch of Windows 3.1. The initiative was designed to produce a modern, 32-bit operating system aimed at the mainstream consumer market, addressing the architectural and usability limitations of running Windows as an operating environment on top of MS-DOS.

Purpose and Architecture of Project Chicago

Project Chicago was designed to meet several ambitious technical and commercial goals:

  • 32-Bit Computing: Chicago introduced a 32-bit architecture featuring preemptive multitasking, multithreading, and support for the Win32 API.
  • Unified OS: It eliminated the need for users to load MS-DOS separately before launching the graphical interface, creating an integrated boot-to-GUI experience.
  • New User Interface: Chicago served as the testing ground for UI paradigms that remain fundamental to modern desktop computing, including the Start menu, the Taskbar, Windows Explorer, and the desktop-as-folder metaphor.
  • Plug and Play: Chicago integrated early implementations of Plug and Play standards to simplify hardware installation.

While "Chicago" served as the overarching umbrella name for the operating system, several sub-components and related projects carried their own designations during this era:

  • Cougar: The 32-bit protected-mode MS-DOS kernel intended to replace traditional real-mode MS-DOS.
  • Panther: The user interface execution engine developed to run on top of Cougar.
  • Cairo: A separate, parallel Microsoft project aimed at building a next-generation object-oriented operating system based on Windows NT. While Cairo was never released as a single standalone product, several of its planned interface and file management features were ported directly into Chicago.

Transition to Windows 95

As development neared completion in late 1994, Microsoft phased out the Chicago moniker in marketing materials. In September 1994, the company officially announced that Project Chicago would be sold to the public as Windows 95, highlighting the release year rather than version numbers. The operating system officially launched worldwide on August 24, 1995.