A Happy Mac is the normal bootup (startup) icon of a Macintosh computer running older versions of the Mac OS operating system. It was designed by Susan Kare in the early 1980s. The icon remained unchanged until Mac OS 9, when it was updated to 8-bit color.
On later New World ROM hardware it was modified into a folder icon bearing the Mac OS logo (itself based on the original Happy Mac); it was removed with the introduction of Mac OS X v10.2, which replaced it with a large grey Apple logo.
When a Macintosh boots, it makes a startup chime and the screen turns gray. After a few seconds, a Happy Mac icon will appear, followed by the Mac OS splash screen, which underwent several stylistic changes. Mac OS versions after 8.5 also included the version number in this splash screen. The Happy Mac indicates that booting has successfully begun, whereas a Sad Mac (along with a "Chimes of Death" melody) indicates a hardware problem.