The Mac OS startup screen is the image displayed by a Macintosh after the Happy Mac icon that indicates bootable media with a proper System Folder has been found. The image is displayed by the operating system while it is loading from the startup disk.
From the original Macintosh System Software through System 7.5, this was a white rectangle with a black border displaying the words "Welcome to Macintosh". This was updated during the Macintosh System rebranding with Mac OS 7.5.1, such that 7.5.3 and 7.5.5 soon switched to a larger colored square with the Mac OS logo. With Mac OS 7.6.1, this completely replaced the original Startup screen.
With specific extensions such as MacsBug installed, further text was also displayed in the dialog. In later versions of the operating system, further loading text was also displayed in this space, including "Extensions Off" if the shift key was held down during the boot process.
It was also possible in the classic Mac OS to create a document containing a single PICT resource (or ID 0 if the file contains more than one), name it "StartupScreen", and place it in the System Folder. This would replace the white rectangle just prior to the loading of INIT resources/System Extensions.
- Graphics by Ray White. 2004.
- Macintosh startup at Wikipedia