The first version of Windows, 1.0, arrived in November 1985. The seminal version meant users no longer needed to type MS-DOS commands - they could move a mouse to point and click their way through screens.
Windows 1 had a colour 16-bit interface, and many of its basic programs - Paint, Notepad, Clipboard, the clock and calendar - are still in current versions.
Microsoft pushed out new versions of Windows 1 each year, but continued supporting the original interface until the version was withdrawn in late 2001. Windows 1.0 required a minimum of 256KB, two double-sided floppy disk drives and a graphics adapter card. To run multiple programs - or when using DOS 3.0 or higher - you'd need a hard disk and 512KB memory.
Fun fact: Windows 1 was originally meant to be called "Interface Manager', but Microsoft's head of marketing at the time convinced the executive team 'Windows' would be more appealing.