RISC OS 3.7 User Guide

7 Other storage devices and filing systems

The last chapter told you about using ADFS hard discs and floppy discs. This chapter tells you about some other types of storage device, and how to control them using their own filing systems.

You'll find out about using DOS and Windows discs, CD-ROMs, PCMCIA memory cards, and RAM (an area of computer memory used as a disc).

Types of filing systems

The RISC OS operating system provides and supports a number of different filing systems, which have been designed to suit the type of storage device on which they are found. Apart from ADFS, the main filing systems are

SCSIFS, used with SCSI discs (up to 512MB incapacity)
DOSFS, used with DOS and Windows discs
CDFS, used with CD-ROMs
PCCardFS, used with PCMCIA memory cards
RAMFS, used with RAM discs
ShareFS, used on an Acorn Access network (see Networking on page 99)
NetFS, used with file servers connected via a network (see Networking on page 99)
NFS, used to communicate with non-Acorn computers on a network (see page 119).

The RISC OS Filer and desktop give a uniform user interface to all these filing systems, but with each system there are a few special features provided; these are accessed from each device's icon bar menu.

Finding out the filing system type

If you want to find out which filing system you are using, look at the name in the title bar of the directory display. This always starts with the name of the filing system.

Using DOS and Windows discs

Your computer can read and write any floppy discs that use standard DOS formats. This makes it easy for you to transfer information between your computer and any computer that can use these formats. Your computer can also format discs in the standard 720K and 1.44M DOS formats (see page 78).

Using DOS floppy discs

You can use DOS-formatted floppy discs in the same way as RISC OS-formatted discs; just put them in the disc drive and click on the floppy disc icon. There are however some limitations:

You should only use DOS discs to transfer files between your computer and a computer that can use DOS discs.
You should not use DOS discs to store RISC OS applications and programs, as anything stored on a DOS floppy disc is subject to DOS naming conventions. This results in filenames being altered and shortened.
To avoid possible data corruption you must dismount DOS discs before you remove them from the floppy disc drive.

The menu options available for DOS files and directories are exactly the same as those for RISC OS files and directories. You can copy and move files between RISC OS and DOS formatted floppy discs. To run DOS applications, you will need the PC emulator application, PC Soft, or a PC hardware expansion card.

If your computer is very low on memory it may not be able to read a DOS disc, returning an error such as 'Disc not recognised - has it been formatted?'.

Transferring files between RISC OS and DOS computers

If you save files from a RISC OS computer to a DOS-formatted floppy disc you can transfer the files to a DOS computer. Similarly, you can transfer files from a DOS computer (or one that understands DOS discs) to a RISC OS computer.

Character conversion

You should be able to read RISC OS text files on a DOS computer. However, DOS and RISC OS use different ' top-bit set' characters, which are not interchangeable. In practice this means that all the letters you can type on the keyboard, except the Pound sign, will be readable. Most other characters generated using !Chars won't be readable and may be translated into different characters on a DOS computer.

When moving files created on a DOS computer to RISC OS the same restrictions on top-bit set characters apply. Some DOS word processors end each line with a carriage return and a line feed; this makes text appear with a [0d] on the end of each line. You can cure this easily by using Edit to replace the carriage returns with nothing. You can search for carriage returns with a Hex [0d] (choose the Hex option in the Find text box).

Some other word processors only use carriage returns at the end of each line. When these files are imported into Edit the text is shown as continuous characters. Use the CR<->LF option in the Edit menu to convert it into lines again. Binary and other non-text files are transferable between computer systems.

Filename limitations

This section shows you how filenames generated on DOS computers and RISC OS computers translate between systems.

On RISC OS computers, filenames are usually limited to 10 characters. On a DOS computer names are limited to eight upper case characters with a three letter extension. For example TESTFILE.TXT is a valid DOS filename.

When copying files from a RISC OS disc to a DOS disc, names are truncated to eight characters and the names are translated into all uppercase. For example Configure becomes CONFIGUR. Bear this in mind (you may need to rename files after copying). The RISC OS file type of an object is preserved. DOS filenames are not case sensitive.
If you are copying a file from RISC OS to a DOS disc, the filename must not start with a /, or contain more than one /, or contain more than three characters after a /.
When copying files from a DOS disc to a RISC OS disc, the filename, including the extension, is truncated to 10 characters. One of the characters will be a '/' which is added to separate the filename from the extension. For example, AUTOEXEC.BAT becomes AUTOEXEC/B.
Filenames are only truncated if the command *Configure Truncate is set to on, which it is by default. If it is set to off, an error is generated. (See the file StarComms in the Tutorials directory.)
You should not give a DOS disc a single-letter name using the letters A to G, or the digits 0 to 7.
Some DOS utilities allow disc names incorporating a '.' (dot) character. Such names are not recognised by the RISC OS Filer, which will report an error such as 'Please insert disc x', where 'x' is the part of the disc name before the dot.

Copying DOS files between DOS discs on a RISC OS computer

When copying from one DOS floppy disc to another (or a DOS hard disc partition) filenames are not truncated. All eight characters, the dot separator and the three character extension are copied. However, when looking at the files in a directory display the 'dot' separator is displayed as a '/'.

File access

Since there is not a complete mapping between RISC OS file attributes and those provided by DOS, access rights are set as follows:

A RISC OS file which is locked will be read only under DOS.
A DOS file which is read only will be locked under RISC OS.

DOS file icons

If you open a directory display that contains DOS files, the RISC OS Filer displays file icons using the DOS file icon.

If you want, you can assign RISC OS file types to DOS file extensions using the *DosMap command (see the file StarComms in the Tutorials directory). This, for example, lets you assign DOS files with the extension TXT the RISC OS file type Text.

Using DOS hard disc files

If you have a DOS hard disc partition (created using a PC hardware expansion card, for example) the Filer displays it with the DOS hard disc file icon. Double-click on this icon to display the files on your DOS hard disc. The Filer treats the DOS hard disc file as a normal directory and allows you access to the DOS files in a RISC OS directory display.

Copying and moving DOS hard disc files

If you want to copy or move your hard disc file, it will be copied or moved as a single file, not as a series of files and directories.

If you want to copy it as a series of files and directories, double-click on the DOS directory icon, and then copy the files from within it.

Deleting DOS hard disc files

If you want to delete your DOS hard disc file, the Delete option on the Filer will delete it as a single file (not as a directory).

You should be very careful not to delete your hard disc file by accident. You could lock it to protect it against accidental deletion - see Using the File/Access/Access details submenu on page 24.

Using CD-ROMs

Some Acorn computers can use a CD-ROM drive. CD-ROMs have their own filing system: CDFS. This is very similar to ADFS, and allows you to read and copy the data from a CD-ROM disc. However, you can't delete files from a CD-ROM, or format a CD-ROM, as they are read-only devices.

A CD-ROM drive may use the same connections as the IDE hard disc drive on your computer (or it may be connected via a SCSI card, or other podule interface). The maximum number of drives supported by the IDE interface is two (including your hard disc drive). If your computer is not fitted with a CD-ROM drive, you may be able to add one yourself - ask your supplier about this.

Sharing CD-ROM resources

If your computer is connected to a network, you can share your CD-ROM drive with other users on the network (or have access to their CD-ROM drives, if they want you to). There are a couple of ways of going about this. See Sharing a CD-ROM on page 102.

Using CDFS

To open a directory display for a CD-ROM, click on the CD-ROM drive icon on the icon bar. The contents of the CD-ROM will be displayed by the RISC OS Filer:

Viewing files stored on PC-format CD-ROMs

You can open RISC OS directory displays for PC-format CD-ROMs. PC file names are translated to a format compatible with the RISC OS environment.

You can view text files using Edit in the same way as usual, and use ChangeFSI (see page 341) to convert a wide range of graphics images to RISC OS sprites or JPEG files, which you can then view and manipulate using Paint or Draw. Some computers can also run the PC programs included on such discs, provided they are fitted with the appropriate expansion card - see your supplier for details.

Playing music CDs

You can play ordinary music CDs using a CD-ROM drive using the CDPlayer application - see CDPlayer on page 337.

Volume control

To control the volume of an audio CD (played using CDPlayer) or any CD-ROM that has audio files on it, choose Volume... from the CDFS icon bar menu.

Using PCMCIA memory cards

Some Acorn computers include support for PCMCIA memory cards. These are similar to floppy discs, in that they store information, files and applications.

There are different types of PCMCIA memory card available, some of which (e.g. ROM, MROM, EPROM and OTPROM) are read-only, and others (e.g. SRAM) which you can write to and format, like a floppy disc.

If your computer is fitted with PCMCIA slots, you'll see an icon on the lefthand side of the icon bar for each slot. These are numbered :0, :1 and so on. When you insert a PCMCIA memory card, the name under the corresponding PCMCIA slot icon will change to reflect the name of the card.

PCCardFS filer

The PCCardFS filing system behaves in the same way as ADFS. For example, you can copy and move files, and format some types of PCMCIA memory card.

Displaying the root directory

If you click Select or Adjust on a PCMCIA slot icon, you'll see the root directory display for that PCMCIA card. Icons in the directory display behave in exactly the same way as in an ordinary ADFS display.

Icon bar menu

If you click Menu over a PCMCIA slot icon on the icon bar, you'll see the same familiar menu that you'd see for a floppy disc, with a couple of exceptions (e.g. Name card instead of Name disc). Some of the menu entries will be greyed out, depending on what type of PCMCIA memory card you've inserted. For example:

You can't Verify PCMCIA memory cards
You can't Format or Name read-only PCMCIA memory cards (e.g. ROM cards).

Formatting PCMCIA memory cards

This works in the same way as formatting a floppy disc. You can format a PCMCIA memory card in one of two ways:

Choose Format/PCCardFS to format the card as a PCCardFS disc.
Choose Format/DOS to format the card as a DOS disc.

If you see a 'Card not formatted' message when you click on a PCMCIA slot icon, you'll need to use one of the above options.

If you see the 'Format not understood' error message, you can format the card as above if you're sure there is nothing useful on it.

PCMCIA I/O devices

There are many different types of PCMCIA card, not just memory cards. Any PCMCIA slots in your computer will accept PCMCIA I/O devices (such as Ethernet cards, or parallel ports) as well as PCMCIA memory cards. If the card in a given PCMCIA slot is an I/O device, the corresponding slot icon on the icon bar will be greyed out, as will all the menu options.

RAM discs

A RAM disc is an area of computer memory that is being used just like a disc drive. It is called a RAM disc, because you use it in a way very similar to a hard or floppy disc. However, the important thing to remember is that objects on the RAM disc are not 'safe' in the way that objects on real discs are safe: they will be lost when the computer is switched off or reset.

The main reason for using a RAM disc is that saving and loading files and applications to or from the RAM disc is much faster than to a floppy or hard disc.

Creating a RAM disc

There are two ways of creating a RAM disc. One method is to use !Boot's Memory configuration window to create a RAM disc of a given size every time you switch on the computer (see page 43).

Preferred method

The preferred method is to use the Task manager to create a RAM disc for the current session only (see Create a RAM disc on page 64). This is because

it's less wasteful of memory
configuring too large a RAM disc from !Boot may cause problems on start-up (e.g. if the disc is larger than the total amount of free space available, or if you physically remove some RAM from your computer and forget to alter your boot sequence). See Troubleshooting on page 71.

The largest RAM disc allowed is 16MB.

Using a RAM disc

A RAM disc is a convenient way of speeding up some operations, at the cost of using some of the computer's memory. Here are two examples:

Copying between floppy discs

When you are copying a group of objects from one floppy disc to another, you have to change the disc after each file or directory. An alternative is to allocate as much space as you can to a RAM disc, copy as many files as will fit into RAM, and then copy them from RAM disc to the destination disc. When you've finished, delete the files from RAM, and quit the RAM disc by choosing Quit from the icon bar menu.

Keeping frequently-used files in a RAM disc

Another common use of the RAM disc is to hold programs and data files that you use frequently. Keeping them in the RAM disc reduces the time they take to load, and may help you avoid having to change discs to find them.

Don't keep files that you are changing in the RAM disc: it's too easy to switch off the computer without transferring them to a permanent storage medium.

RAM disc icon bar menu

The RAM disc has its own icon bar menu with options specific to the filing system.

To see how much space is available, click Menu on the RAM icon, and choose Free. This displays the total free and used space, in KB.

You can remove the RAM disc from the icon bar by choosing Quit. If the RAM disc is not empty you'll be warned that you will lose its contents if you go ahead.

RISC OS 3.7 User Guide - 21 JAN 1997