Features of Amiga Executable Files
Amiga executable files can be launched either from the graphical shell of the Amiga, the Workbench, from the Amiga's command line interpreter (called CLI, later AmigaShell), or even from a file manager tool.
No particular filename extension is required for Amiga executable files. For example, the calculator applet "Calculator" can be renamed to "Calculator.com", "Calculator.exe", "Calculator.bin", or even "Calculator.jpeg". These are all valid names for programs or tools, because AmigaOS does not differentiate between file extensions.
Some operating systems, such as MS-DOS or Windows, need filename extensions to recognize that a file is an executable. Usually, this extension is a three-character acronym separated from the real filename by a period ".".
AmigaOS adopted another method to recognize it is dealing with a valid executable. There is a particular sequence of bytes in the file header, yielding the hexadecimal value $000003f3. This sequence, which signifies an executable file and lets it be self-running, is called a magic cookie (from the magic cookies in Alice's Adventures in Wonderland by Lewis Carroll).
This kind of solution to identify executables on the Amiga was taken from similar solutions which were adopted by UNIX/Unix-like operating systems, where magic cookies are called magic numbers.
In Unix, a file attribute bit "x" (for eXecutable) must also be set, only in this case the operating system will check the magic number. If there is a correct magic number in the beginning of the file it is considered a binary executable. If a file starts with characters "#!" then it is considered to be a script instead.
Read more about this topic: Amiga Hunk
Famous quotes containing the words features of, features and/or files:
“Art is the child of Nature; yes,
Her darling child, in whom we trace
The features of the mother’s face,
Her aspect and her attitude.”
—Henry Wadsworth Longfellow (1807–1882)
“The features of our face are hardly more than gestures which force of habit made permanent. Nature, like the destruction of Pompeii, like the metamorphosis of a nymph into a tree, has arrested us in an accustomed movement.”
—Marcel Proust (1871–1922)
“The good husband finds method as efficient in the packing of fire-wood in a shed, or in the harvesting of fruits in the cellar, as in Peninsular campaigns or the files of the Department of State.”
—Ralph Waldo Emerson (1803–1882)