Windows 7, a major release of the Microsoft Windows operating system, was available in six different editions: Starter, Home Basic, Home Premium, Professional, Enterprise and Ultimate. Only Home Premium, Professional, and Ultimate were widely available at retailers. The other editions focus on other markets, such as the software development world or enterprise use. All editions support 32-bit IA-32 CPUs and all editions except Starter support 64-bit x64 CPUs. 64-bit installation media are not included in Home-Basic edition packages, but can be obtained separately from Microsoft.