The Amiga uses AmigaOS, a unique OS with special advantages. It's extremely compact and still powerful and thus especially fast. It was the first operating system with Multitasking and a Graphical User Interface (GUI) in color for the mass market.
AmigaOS is modularly designed and consists primarily of function libraries. It can get expanded with new libraries at any time, very easily and in a system compliant way. This makes the AmigaOS extremely flexible.
AmigaOS had time to mature for over 10 years now. During this time there were several version upgrades with big enhancements of its functionality. But still AmigaOS grew faster with every new version because of increased efficiency!
Flexible, compact, fast - the attributes of a truly modern operating system.
AmigaOS features preemptive multitasking. This means a program does not need to be explicitly designed for multitasking and still it works effectively together with many others simultaneously. The reaction on user actions is instantaneous, the mouse cursor follows the mouse moves without a delay.
AmigaOS is extremely efficient in regards of the amount of memory and computing time required. With only 1 or 2 MB RAM, you can already multitask several full-blown application programs without any noticeable delays. And the AmigaOS and typical applications need relatively little hard drive space as well!
Theoretically no, practically yes. For a so-called "realtime OS" you must be able to guarantee maximal reaction times after external signals. For AmigaOS such guarantees are not given, but on the other hand it's so efficient and fast in reaction that it is already used in many realtime control applications in the industry.
The Amiga Operating System was created in a time when "OO" was not yet a hype term. But it is state of the art and incorporates many ideas from object oriented design philosophies. This is one of the reasons why the OS is so compact, efficient, and simultaneously flexible.
The AmigaOS is since its first days (1985) a 32-bit OS, thanks to the internal 32-bit architecture of the Motorola microprocessors. Also every application software is thus 32-bit. So you do not need a new operating system and a completely new set of application software to exploit the 32-bit features of the current generation of processors, it happens automatically.
There are assemblers, C, C++, Pascal, Modula 2, Oberon, Fortran, Basic compilers, and several special or unique languages like BCPL, E, scheme, Cluster, ARexx, Lisp, or Prolog. The biggest part of the AmigaOS is written in C, the time-critical parts in assembler. For most languages there exist highly reputed commercial compiler packages, as well as Public Domain and Shareware versions that make it easier for beginners to enter the Amiga programming world. Programmers are supported by system documentation in book form, the ROM Kernel Manuals, and in electronic form on floppy or CD with Autodocs, Includes, Tools, and examples.
The Amiga uses microprocessors of the 680x0 family by Motorola, where the x stands for the ciphers 0, 1, 2, 3, 4, or 6 currently. Already the first member of this family is internally structured with 32-bit width, though it appears more as a 16-bit type externally. This processor family is especially flexible to program and offers the programmer many possibilities to optimize his software. Key words for the expert are "flat memory model without limiting segmentation", a big number of internal, really general-purpose registers, and a "nearly orthogonal command set".
With the graphics on the screen, a normal, but of course abstracted bureau environment is displayed where e.g. files are kept in drawers. With your mouse you mark and manipulate these objects, you select items from menus or trigger certain actions by clicking on some graphical symbol. Thanks to the design of those symbols, their function is immediately visible and you can work with high productivity without needing to learn much about it. That's why the part of the AmigaOS which handles these elements of the GUI is named Intuition.