Generalities : Every modern OS comes with a human understandable interface called a “Graphical User Interface”. The first idea of a GUI comes from the 60s and the reflexion about HMI (Human-Machine Interface). You use a GUI everyday, so maybe you don’t even think about it, but, if you think about the beginnings, the first computers were commanded with paper sheets where we make little holes. Thoses sheets were putted into a “reader” that send the informations to the really not powerfull calculator. Still today, designers imagine new ways of giving commands to the computer : radio, voice, movements… Mouse and windows emerged from a Mr called Engelbart, in the early 60’s. The Workbench : Ofcourse, an Amiga can be commanded only with the command line (the “Shell”), and does not need any disks to get to a simple command line interface. Anyway, you cannot do a lot of things, as the commands themselves (for example the “dir” command) comes onto the Amiga Workbench disk. And, what are really impressive on an Amiga are the multitasking / multimedia capabilities, so let’s get to the “Workbench”. Except the A1000, all amiga computers came with a 256Kb or 512Kb embedded ROM including the software libraries necessary for the use of the chipset, and the work of the Amiga OS. This is, in some ways, like the BIOS we know, but with a bunch of routines that allow the pictures/gui windows/drive operations, sound playing… to work. So it is an “extended BIOS”. We can way that the OS itself was “ONBOARD”. At this time, most of the OSes we knew were mono-task. Even OS/2 that came a little bit after was at its beginning a mono-task OS (Zindoz was monotask until NT4 core). Unix was, if i’m right, the only OS at this time to offer multitasking to the peoples. Amiga OS was the second one, and in a way, there is a correlation in the organization of the OS files on the disk between those two OSes : one drawer for the executables, one for the libraries, one for the devices… Even the shell syntax was similar. Multitasking was : you were able to do different stuffs at the same time, like opening a document while listening to music, and rendering a 3D picture in an other window. The speed was good, there was no lagging, and NO CRASHES due to the system.  Today, you can find this usual, but, remember that your Zindoz OS waited for years even after the end of Amiga Inc. to be able to do it well. Ofcourse, as there was no memory protection, you could always make your computer crash if you wished it, are a bad programmer, or use some ROM patches without thinking. Here are some pictures of The Workbench :
This is a well known picture of the capabitity for the Amiga to show multiple “SCREENS” with different resolution at the same time ! Even today, no machine is capable of that.
Here is the Workbench 2 screen.
The PREFS drawer.