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AmigaOS 4.0 - About OS4 - File System

The Amiga File System
AmigaOS 4.0 stores information on devices that are organised according to a system of directories, subdirectories, and files known as a File System. Directories (or 'drawers' as they are called) are arranged in a hierarchical system often referred to as a tree, since its branching diagram looks like a family tree. The branches are drawers, any of which can include other drawers, and at the end of these branches are the files (like leaves), for example:

Volumes and Devices
To gain access to a file on a particular disk, you can refer to the disk by its volume name, such as OS4: or Workbench:. When you refer to a disk by volume name, the system will search all of the available drives for the disk, If it cannot find a disk with that name, a requester will appear asking to insert the volume in any drive.

Another way to refer to disks is by device name. A device name refers to a particular device, such as a hard drive partition or a floppy disk. For example, DF0: is the device name of the AmigaOne's internal floppy disk drive. If you save a file to DF0: it will be saved to whichever disk is inserted in DF0: at that time, irrespective of its volume name. Other common device names are DH0:, DH1:, DH2: etc for the hard disk partitions, CD0:, CD1: etc for the CDROM and DVD drives, CON: for the console device, PAR: for the parallel port, PRT: for the printer device, SER: for the serial port and NIL: for the dummy device where output can be redirected if it is not required.

The RAM Disk represents another type of device, RAM:. The RAM: device is a portion of the AmigaOne's internal memory that can be used as a storage device, and used like any other device, except that all information in RAM: is ost if the AmigaOne is rebooted or powered off.

Pathing
To identify a particular file you must specify the complete path that lead to that file. This begins with the volume or device name followed by a colon (:) (e.g. OS4:, Workbench:, etc), and then the names of each drawer and finally the file name, all of which must be separated by forward slashes '/', for example:

Workbench:Drawer1/Drawer2/Drawer3/File1

Files and Drawers
While earlier versions of the Amiga File System limited names to 30 characters, file and drawer names under OS 4.0 Final are unrestricted and can be upper and/or lower case, numerals and some special characters but not colon ( : ), semicolon ( ; ), asterisk ( * ), backward slash ( \ ), forward slash ( / ), question mark ( ? ), back apostophe ( ` ), hash sign ( # ) or percent ( % ).

However it should be noted that the Amiga Operating System is NOT case-sensitive, so a file name of 'THIS' is the same as 'this' and also the same as 'This'. Unlike some other Operating Systems, there is no need to put a suffix on the end to identify what sort of file it is, but there is nothing to stop you using this naming standard for compatibility with other systems.

It should also be noted that file sizes cannot currently exceed 2GB.

Assigns
With AmigaOS 4.0, many commonly used drawers are assigned a short logical device name rather than their usual names or complete paths. In addition, multiple drawers can be assigned to the same logical device name, and this has the effect of concatenating them together as though they were one drawer.

Each time the assigned logical device name is referenced to, the full path name(s) will be substituted automatically.

You can obtain a complete list of all assigned logical device names from the Shell by typing ASSIGN and pressing <Enter>, and the following discussion on the System Disk also shows logical device names where they are used.

Understanding the System Disk
When you boot your AmigaOS 4.0 system, the disk that you boot from can be called anything that you like, (e.g. OS4, Workbench, etc) but to the operating system it is known as "SYS:". In order to boot the system, this disk must be 'bootable' and must have all of the drawers and files required by the operating system.

These drawers are as follows (shaded drawers are normally invisible):

Drawer Name Logical
Device
Name
Description
C C: contains all of the system commands that can be executed from the Shell or by scripts such as the Startup Sequence. Many users also find it convenient to add commonly used third-party commands or programs here as well. None of the files in this drawer have icons associated with them because they would not normally be run from the Workbench.
Classes CLASSES: contains all of the object classes that are supported by the system. When a program needs to process an object, it can use the information stored here to process the object without really having to know much about it, to the extent that new object classes can be introduced and existing programs can use them without having to be modified. This applies to objects like gadgets, datatypes, images, pop-ups, etc. None of the files in this drawer have icons associated with them because they would not normally be run from the Workbench.
Devs DEVS: contains all of the device drivers that are supported by the system. Unlike many of the other drawers, you may need to add device drivers to suit your particular configuration, and six drawers icons are normally visible when you open this drawer.
  • Datatypes
  • DOSDrivers
  • KeyMaps
  • Monitors
  • NetInterfaces
  • Printers
The Devs drawer also contains numerous other device drivers and configuration files which would not normally need to be accessed. One exception may be the AHI and sound card drivers which are located here, but not in one of the above drawers.
Fonts FONTS: contains all of the font information available to the system. If you examine the contents of the drawer you will see all of the vector fonts listed, while the bit-mapped fonts are stored in their own drawers.
Internet contains all of the tools necessary to connect to the Internet and is used to store your configuration parameters for connecting to your ISP(s). It also contains Action logs, Connection Logs and Error reports.
Kickstart contains all of the resident programs, device drivers and libraries that are loaded and executed during the boot sequence, effectively forming the kernel of the AmigaOS 4.0 system.
L L: contains the device handlers, software programs that act as intermediate stages between the Operating System and the device. Most handlers are treated as if they were actual physical devices, and are referred to by their device name. However, all handlers must be named in the Mountlist entry for their respective devices. Handlers are not called or manipulated directly by users, but by programs. New handlers may be supplied with some devices or programs and should be added to the L: drawer.
Libs LIBS: contains a variety of software routines and maths functions commonly used by the Operating System and applications. New Library routines may be supplied with some programs and should be added to the LIBS: drawer.
Locale LOCALE: contains all of the information related to the various languages and localities supported by AmigaOS 4.0, and has drawers for countries, languages, characters sets, catalogs, flags, and help information.
MUI MUI: contains all of the support tools and configuration information for the MagicUserInterface which can be used to customise the look and feel of your system. The installed MUI system is not registered, so most of the non-essential interface design settings are disabled, although they can be temporarily activated for testing and evaluation. If you want to use these facilities permanently you should register it.
Prefs contains all of the programs used to configure your system, such as display resolution, Workbench backgrounds, sound cards, printer devices, locality preferences and so on, all of which is discussed in detail in the Preferences section.
S S: contains the files used during system startup, and two in particular are very important.
'Startup-Sequence' contains all of the commands necessary for the Operating System routines, including all of the logical device name assigns, as well as critical pathing information - it is best that you don't change this file unless you know what you are doing and understand the consequences.
'User-Sequence' contains the additional startup routines that you require for your system and is for your use. If you make an error, the critical startup processes will still be in place and you should be able to fix any errors after ignoring any warning messages that might be output. Some programs or processes will either make changes here during the install process or request you to make changes if desired.
Storage contains any device drivers that are not active on your system, and looks similar to the Devs: drawer above. Device drivers should never be deleted from the simple, but moved from Libs to Storage, and vice versa to activate them.
System contains all of the system programs that may be executed from the Workbench. Two important programs located here are 'USBStart' and 'USBStop' for activating and de-activating the USB port.
(Tools) prior to OS4.0 Final this drawer contained some of the commonly used system and utility programs from Third Parties. However this drawer is now obsolete and no longer part of the install, and all programs previously found there are now found either in the System or Utilities drawers.
Trashcan a special drawer that contains files that you no longer need and may will to delete, but rather than delete them permanently, they can be stored here until you are ready to do so.
Utilities contains commonly used system programs, including many developed by third parties.
WBStartup contains any programs that should be run when the system is started.

Now let's look at the Workbench in more detail.

Disclaimer: Amiga Auckland have prepared the above information for the use of its members based on our experiences and as such is subject to revision at any time. Amiga Auckland cannot guarantee any of the information and cannot be held accountable for any issues that may result from using it.


Copyright 2006 Amiga Auckland Inc. All rights reserved.
Revised: December 24, 2006.