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RISC OS 3 User Guide


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 will 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

For more information on the last three See the section on Networking)

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.

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:

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.

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:

  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.

  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.

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) 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.

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:

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:

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.

The preferred method is to use the Task manager to create a RAM disc for the current session only (see Create a RAM disc). This is because configuring too large a RAM disc from !Boot may cause problems on start-up, for example 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. However if you have plenty of RAM in your computer you may prefer to configure a RAM disc using !Boot.

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:

RAM disc icon bar menu

The RAM disc has its own icon bar menu with options specific to it.

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. in the same way as with other drives.

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.

You can change the size of the RAM disc by dragging its slider in the Task Manager. However you can only do this if the RAM disc is empty.


RISC OS 3.7 User Guide - 21 JAN 1997

This edition Copyright © 3QD Developments Ltd 2015
Last Edit: Tue,03 Nov 2015