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1 . How to use this manual

If you have purchased a disk interface from Opus Supplies Ltd., and if the interface

has not been fitted into your computer by a dealer then look at the fitting

instructions in chapter 12, read and follow them carefully. If you do not feel

competent to follow the instructions then contact your local dealer for assistance.

If you have never used disc drives before you should read chapters 2 and 3 which

explain how to use them, and how to look after your discs. You should then read

through chapter 4, carrying out the exercises given, to help familiarise you with

your new equipment.

Chapter 5 provides a detailed explanation of the commands available in the Acorn

DIFS, and should be read by users of Opus DDOS and CHALLENGER as these

systems include all the commands provided by the Acorn DFS, (and many more

besides!)

The extensions provided by Opus DDOS are explained in chapter 6, it is

suggested that new users should read chapter 5 before proceding to the extra

facilities provided by Opus DDOS. Users of the CHALLENGER should also read

this chapter, since all facilities provided by DDOS are available to users of the

CHALLENGER.

CHALLENGER ADDENDUM

You will find that most protected programmes will boot immediately on your

Challenger.

However for some software: ie. ELITE, it is necessary for the disc catalogue

to be loaded at EOO.

To enable these programmes to load you should type the following:

*ENABLE CAT (RETURN)

You will then be able to boot the programme as normal.

2. Disc drives and discs

Installing a disc drive unit (Acorn DFS and Opus DDOS)

The BBC microcomputer can be fitted with one or two disc drives. When two are

fitted, they are usually in the form of a dual unit in a single casing.

A disc drive is a very simple device to look at. It is a long metallic box with two

cables attached to it. At the front are one or two 'letter-boxes' through which the

discs will be 'posted'. The letter-boxes have doors which are opened and closed

either by a lever, which turns through 90 degrees, or a flap.

There may also be an indicator light on each drive which lights when the drive is in

use. At the back of the unit, there may be an on-off switch, of which more later.

Of the two cables, one is a flat ribbon cable fitted with a flat 34-way plug, which will

connect to the BBC. The other is a power cable. If the disc drives have their own

power supply, then you will need to fit an appropriate mains plug to this lead, with

a 3-Amp fuse. If the disc drives are to be powered from the BBC, the cable will

already be fitted with a 6-way connector.

To fit the drive unit, turn off and unplug the BBC. Lift up the computer,

underneath you will observe a number of label led sockets. If you have an

Opus RAMDISC insert the 34-way plug into the socket marked 1 MHz

Bus', if you are using Acorn DFS or Opus DDOS insert the 34-way plug

into the socket marked 'Disc drive'. Normally, this is possible in only one

way because the plug has a small lug on top which must fit into a

corresponding notch in the socket. Alternatively, the ribbon cable will have

a red stripe down one side, and the plug should be aligned so that this

stripe goes to the side of the socket marked by an arrow head.

If there is a 6-way power connector, this should be connected to the socket

marked 'Auxiliary power socket'. It is not possible to connect this plug in other than

the correct orientation. If the drive unit has its own power supply, plug in the mains

power lead.

The drive unit should be positioned on a firm horizontal surface. Open the doors

and remove any cardboard transit packing slips. Keep these for possible future

use.

Close the doors again. Power on the BBC and the drive unit. Nothing should

happen at this stage. If the indicator lights do come on or the drive makes

unexpected noises, either the drive has been incorrectly connected to the BBC, or

the disc filing system upgrade has been incorrectly fitted in the BBC. Turn off the

BBC and the disc drive and recheck all steps, if necessary refitting the disc

upgrade.

If all is quiet, type *. (RETURN) on the BBC keyboard. The drive (the upper drive of

a dual drive unit) should now spin, making a constant whirr, and the indicator light

should be on. If not, check the switch on the back of the drive is on. Check the

mains connection or the 6-way power connector. Check the ribbon cable

connection.

To stop the drive spinning, press the BREAK key. The drive unit is now installed

and ready for action, but before you start using it you need to know a little about

disc drives and floppy discs.

Types of disc drives

Not only do disc drives come singly or in pairs, but each drive can be either single

or double sided (which means that they can use just one or both sides of a floppy

disc). The numbering of the disc drives on the BBC reflects these combinations.

A disc in a single, single-sided drive is said to be on drive 0. In a single double-

sided drive, the upper side of the disc is on drive 0 and the lower side on drive 2.

With dual drives, a disc in the upper drive is on drive 0 or 2, as above. A disc in the

lower drive is on drive 1 (upper side) and drive 3 (lower side).

A disc drive can be either a 40-track or an 80-track drive, and in some cases, can

be switchable between these modes (by the 40-80 switch at the back of the drive).

An 80-track drive can store twice as much information on a floppy disc as can a 40-

track drive.

Normally 40-track discs must be read by 40-track drives, and 80-track discs by 80-

track drives. DDOS can also read 40-track discs on 80-track drives.

Floppy Discs

You will have purchased at least one box of blank floppy discs, so now is a good

time to study one, in conjunction with the diagram of the floppy disc.

The disc will be in a paper or cardboard protective envelope. Whenever a disc is

not being used, return it to its envelope, and then to a suitable storage box, to

protect it from dust. Dust can not only destroy a floppy disc and the information on

it, but it can wreck the disc drive as well.

When removed from the envelope you will see three areas of exposed magnetic

recording surface; around the central hole, in a smaller offset hole called the index

mark, and an elongated radial hole called the head slot. Never touch any of these

surfaces, as the grease from your fingers may well ruin the disc.

Despite their name, floppy discs are reasonably robust when handled with care.

However, they can easily be destroyed with heat (a carelessly placed coffee cup),

by strong magnetic fields (close to a television or monitor) or by physical stress

(writing onto the cover with a ball-point, for instance).

As well as having to survive all these environmental hazards, the information on

floppy discs can quite easily be overwritten or deleted by human error. Because of

this, it is essential that you keep at least one copy of all discs which hold

information.

Discs come supplied with sticky identification labels. You should always label

every disc as soon as it has any useful information on it. Put as much information

as you need on the label to remind you what the disc holds. Indicate whether the

disc is a master or a copy. It is better to prepare the labels before sticking them on

to the disc; if you must write on a label which is already on the disc, use a felt

tipped pen with no great pressure.

One way of reducing the chance of accidental loss of information is to use the

write-protect tags which are supplied with the discs. They are sticky black or

metallic tags. If you completely cover the small write protection notch on the side

of a disc by one of these tags, a disc drive will be unable to alter the information

on the disc in any way, regardless of what you tell it to do.

It should be noted here that floppy discs have as many varieties as do disc drives.

Discs are described in terms of the best performance that can be expected from

them. Thus the cheapest discs are described as 40-track (sometimes 48 tpi),

single-sided, single density, and should not be used for double density recording,

for instance.

The best discs cope with 80-track (96 tpi) and double density, and are double

sided. We would recommend that you always buy best quality double density

discs, specified for 80-track (96 tpi) if you have 80-track drives, and double sided if

you have double-sided drives. As floppy discs are relatively cheap, any other

strategy is false economy.

Disc formats

A brand new floppy disc is covered on one or both sides with a uniform coating of

magnetic recording material with no structure. Before such a disc can be of use it

must be given structure. It must be formatted.

When formatted, a disc is divided into concentric rings called tracks. There are 49

or 89 tracks per side, depending on the disc drive.

Each track is itself divided into sectors. Standard BBC single density discs have

10 sectors per track. DDOS also offers double density format, in which each track

has 18 sectors.

Each sector contains 256 data bytes, plus some control information. Thus a 40-

track disc recorded in single density will hold 40*10*256 = 1 OOK bytes of data per

side, similarly an 89 track disc recorded in double density will hold 80*18*256 =

360K bytes of data per side.

As well as the basic track/sector structure, each disc is divided into volumes. A

volume consists of a catalogue and one or more sectors available for data

storage.

Standard single density discs consist of a single volume, whereas DDOS double

density discs hold up to 8 volumes. Volumes have single letter names in the

range A to H.

3 Files

A file is the basic unit of information storage in the filing system. Each volume may

contain up to 31 files.

A file consists of data and a catalogue entry. The data is a collection of bytes

stored in consecutive sectors on a disc. Each data byte may take any value

between Q and 255.

The catalogue entry is a collection of attributes of the file. These are the entry

name, the lock, the load address, the execution address, the byte length, the

allocated sector length, and the address of the first data sector.

6

The entry name is the primary method of access to a file. lt is unique within the

catalogue. It consists of a single letter directory name, a fullstop, and a filename of

up to 7 characters. Neither the filename nor the directory name may contain the

characters . : # *. The filing system makes no distinction between upper and lower

case letters in entry names, or anywhere else for that matter.

In Acorn DFS the full file specification includes not only the entry name, but also

the drive name, preceded by a colon and followed by a fullstop. Thus

: 0. $ . FRED

specifies the file named FRED of the directory $ on the disc in drive 0. In fact, this

could probably have been typed as

FRED

because the filing system will substitute defaults for all the missing fields. Initially

these defaults are drive 0, directory $ but the user may change them with the

*DRIVE and *DIR commands, and the new defaults will be used until they are set

again by the user, or until a reset (BREAK).

In DDOS the full file specification includes the entry name and the volume and

drive names. Thus

: OA. $ . FRED

specifies the file named FRED of the directory $ in volume A on the disc in drive 9.

The default volume is initially volume A, and may be changed by the user with the

*DRIVE command.

Returning to the catalogue attributes, the lock is an on-off switch. When the lock is

on, a file cannot be altered in any way; neither the data nor the catalogue entry can

be modified or destroyed. The file can still be read.

The load and execution addresses are used by various file system services

concerned with manipulating whole files.

The byte length of a file is the number of data bytes, which may be zero. The

allocated sector length of a file is the number of sectors set aside for the file on

disc. Normally it is just sufficient to store the data bytes, and it can be derived from

the byte length:

sector length = (byte length + 255) MOD 256

The address of the first data sector is used by the filing system to access the data.

Opening and Closing Files

There are several file system services which are concerned with manipulating a

file as a single entity. However, when access to individual bytes is required, a file

must be accessed through a channel.

A channel can be attached to a single file. the file has then been opened. To close

a file is to detach it from the channel.

Certain additional attributes are associated with accessing a file through a

channel. These are the channel number, the write permit, the pointer and the

buffer.

The channel number identifies a particular channel. Acorn DFS and DDOS make

five channels available, numbered 17 to 21. Other filing systems, such as the

cassette filing system, use a different range of channel numbers.

The write permit is an on-off switch. When the switch is on, data can be written to,

and read from the channel. When the switch is off, the channel can only be read.

The setting of the write permit is determined by the open mode. If the file is

opened for input, the write permit flag will be off. If a file is opened for output or

update, the write permit flag will be on.

More than one channel can be attached to a given file, so long as they all have

their write permit switch off i.e. so long as they are all open for input.

When a file is to be opened for input or update, the file must already exist. When a

file is to be opened for output, a new file of zero length is created, replacing any

existing file.

When a file is opened for update, or is opened for output and replaces an existing

file, the allocated sector length is initially set to that of the existing file. When a file

opened for output does not replace an existing file, the allocated sector length

starts at 64.

The pointer is an index of an opened file's data bytes. When a file is opened, the

pointer for the channel is set to zero. The byte read or written to a channel is the

byte indexed by the pointer.

The pointer is automatically incremented by one after each byte is read or written.

The user may also set the pointer explicitly.

If the pointer is greater than or equal to the file length, an attempt to read a byte will

fail with an end-of-file (EOF) condition. If instead a byte is written to the file, the byte

length of the file is increased by one. If the file is

then too long for the allocated sector length, the file is extended by adding to it as

many free sectors as possible. This will fail if the file has already reached the end

of the volume or the start of another file's data sectors.

The buffer is a 256-byte area in memory in which is held a copy of the sector from

which the last byte was read, or to which the last byte was written. If the next byte

to be read or written is in the same sector, the filing system need not actually

transfer the sector to or from disc, but can use the buffer copy instead. This

considerably speeds up access to files.

Of course, when a new sector is required, the filing system will have to flush the

buffer (that is, update the old sector to disc if it has been changed), and then read

the new sector into the buffer. The filing system will also have to flush the buffer

when the file is closed, and the user may explicitly flush a buffer at any time.

Sequential Access and Random Access

A file is sequentially accessed when it is read or written from the first to the last

byte in order. Sequential file access does not require the explicit use of the

pointer, as the pointer is automatically incremented after each access. Sequential

access is the most efficient way to exploit the buffer.

Any other mode of access is random access. The pointer is used to explicitly

control which byte is accessed. The data bytes may be accessed in any order,

possibly more than once or not at all. A random access file is similar to a single

dimension BASIC array, except that a random access file can be extended beyond

its original size.

Random access is appropriate when the next byte to be accessed is determined

by the input from the keyboard. A typical random access program would be the

implementation of a spreadsheet.

Fast as disc access is, badly-designed random access files can be very

inefficient to access. Thus in the spreadsheet example, if the file were divided into

columns, and then each column into rows, the program would run orders of

magnitude slower than if the file were divided into rows and then columns. This is

because a spreadsheet will normally compute and display all the results for a

given row before moving onto the next.

File Types

The filing system does not distinguish- between sequential and random access

files. Indeed the same file can be accessed in both ways. More generally, the filing

system does not distinguish between the different uses made of files. It considers

a file to be a collection of data bytes, and some catalogue attributes.

However, a file is usually useful only if a particular interpretation is placed on the

value of its data bytes. The appropriate interpretation for a given file is known as

the file type, of which there are a few standards.

A text file is a sequential file of printable characters and cursor movements such

as space, tab, backspace and newline in the ASCII character code.

Such files are commonly known as 'ASCII files', but this is less accurate than 'text

files' since the term 'ASCII' refers to a particular interpretation of ANY value in the

range 9 to 127, which includes some characters which are not printable on the

BBC computer.

A Basic program file is a sequential file of BASIC tokens and text that represents a

Basic program. Tokens are described in chapter 43 of the User Guide.

A Basic data file is a sequential file of Basic data items (integers, reals, and

strings) generated using the PRINT# Basic statement. Such a file can be read

using the INPUT# Basic statement. A random access Basic data file also requires

the use of the PTR# Basic statement.

A Binary program file is a sequential file of machine code instructions and/or

binary data that, when loaded into memory, forms a working machine code

program, or some part of one.

A binary data file describes any file other than one of these defined types. Its

interpretation depends on the programs that access it. In Basic, a binary data file

is generated using the BPUT# statement and read using the 13GET# statement. A

binary data file can be interpreted sequentially or as a random access file.

4 Getting Started

Formatting

Before you can store any information on a disc it is necessary to format your new

discs. With Acorn DFS the program for formatting a disc is not present in the ROM

which was installed in your BBC when the disc interface was fitted, and must be

loaded from disc. Opus DDOS and CHALLENGER both contain the formatting

program in the ROM installed in your BBC with the disc interface. If you are using

Acorn DFS take your master utility disc which was supplied with your disc drive,

and ensure that it has a write protect label on it. If it does not have a write protect

label on it, put one on, you do not want to accidentally erase your only master disc!

Insert the master disc in drive Q, this is the top drive of a dual system. If your disc

drive is a 49-80 switchable, ensure the 40-80 switch is set to the 80 track position.

Type in the command:

*FORMAT

Press the RETURN key at the end of the line. The disc drive will whirr and the

indicator light will come on. In a moment the formatting program will be loaded

and will ask you some questions. Remove the master disc at this point.

If you have Opus DDOS or CHALLENGER you do not need to insert a master disc,

just type the command as above.

The formatting program will ask you which drive you wish to format the disc in, use

drive Q in this case, and how many tracks you wish to format. If you are using an

80-track drive select 89, if you are using a 40-track drive select 40. If you are using

DDOS or CHALLENGER you will also be asked which density you wish to use,

select single density in this case.

When you have answered these questions insert a new disc in drive 0 and when

the formatting program says 'are you sure' answer 'y'. The formatting program

asks for this confirmation because when you format a disc all previous

information is erased.

Saving and Loading BASIC programs

Whenever a computer language is used on the BBC, it uses the current filing

system for saving and loading programs, and for all file handling. A BBC which

does not have a disc interface fitted uses the tape filing system to load and save

programs. When a disc interface is fitted the disc filing system is automatically

made the current filing system, and all the commands which were used with the

tape filing system can still be used,

but now programs are loaded and stored to disc and files are opened to disc. It is

not necessary to change your programs provided that you have used file names

which are also legal disc file names.

Type NEW to clear the BBC of any previous programs, and then type in the

following program.

10 CLS 20 PRINT"Programs are quicker from disc" 30 END

Save the program on your newly formatted disc, calling it ---FIRST-by placing the

disc in drive 0 and typing

SAVE "FIRST"

The indicator light on drive 0 will come on and the program will be saved onto

disc. You can now check that it is there by typing

*CAT

which will show you the files on the disc. Remove the disc from your disc drive and

switch off the BBC; you should never switch your BBC off or on with discs in the

disc drive, or the discs can become corrupted. Switch the BBC back on and insert

the disc into the disc drive. To reload the program ---FIRST-type

LOAD "FIRST"

You may now type LIST to see that it has reloaded properly.

You can see that the statements in BASIC for handling files on disc are the same

as those used with tape, with some extra commands allowed. The complete list

of BASIC statements, described in the BBC User Guide, which work with the disc

filing systems in the same way as with tape is:

BGET#, BPUT#, CHAIN, CLOSE#, EOF#, INPUT#, LOAD, OPENIN, OPENOUT,

PRINT#, SAVE

The BASIC statement OPENUP is not described in earlier User guides, and is not

available with BASIC version 1. It has the same syntax as OPENIN, and

OPENOUT, but the file is opened for update. OPENOUT performs the same action

in BASIC version 1.

The EXT# and PTR# statements are described in the BBC User Guide, but are not

available with the tape system. EXT# returns the byte length of an open file. PTR#

either returns the pointer of an open file, or resets the

pointer to a user specified value. The PTR# statement enables the BASIC

programmer to use random access files.

Transferring from tape to disc

If you have had your BBC for some time you will have some programs stored on

tape, and will probably prefer to have these stored on disc. If these are

commercial programs which use machine code this is not always easy, and we

would recommend you use one of the programs sold especially for doing this. If

the program which you wish to transfer is written in BASIC and is not too large,

then it will transfer to disc quite easily using the following procedure.

Type

*TAPE

this selects the tape filing system. Now load the program in the usual way, if the

program is the next one on the tape you may type

LOAD " "

press play on the tape recorder, and wait for the program to be loaded. When it

has loaded reselect the disc filing system by typing

*DISC

Acorn DFS and Opus DDOS both require memory for their operation, and lift

'PAGE' from &0E00 to &1900. This reduces the memory available for programs

and will prevent those programs which use nearly all available memory, and

those which use machine code in fixed positions from working.

Using Text Files

The filing systems provide some simple utilities to manipulate text files. To create

a text file called, say,---NIIVIZO-from the keyboard, type

*BUILD NIMZO

and save the program to disc. Make sure that the name of the file is only seven

characters long. If you wished to call the program ---FRED-you would type

SAVE "FRED"

and the filing system will behave just as if the four OS commands had been typed

in at the keyboard.

There is an even neater method of executing a sequence of commands. First the

commands need to be in a text file called $.!BOOT. There is no need to rebuild the

file - just change its name:

*RENAME START !BOOT

Now type the command

The filing system will now prompt with a line number for each line of text to be

entered into the file :0.$.NIMZO. When you nave typed all the lines you want, press

the ESCAPE key to terminate the file creation. The screen might now show:

To check the contents of NIMZO, you can type

*LIST NIMZO

to display the text in NIMZO with line numbers, or

*TYPE NIMZO

to display the text without line numbers.

Notethat *LIST and *TYPE are only suitable for text files. Another command

*DUMP should be used with non-text files. It displays not only the printed

representation of any text in a file, but also the hexadecimal coding of the

characters therein.

If you *LIST or *TYPE or *DUMP a long file, it is usually best to turn on the BBC

page mode first, by typing CTRL-N. If you want to stop listing before the end of a

file, just press ESCAPE at any time.

One common use of text files is to encapsulate an oft-repeated sequence of

commands, which can then be executed using the *EXEC command. So for

example:

This is a sequence of commands which you may always wish to execute when

you switch on the BBC. Now that they are captured in the text file START, you can

execute them all by typing

*EXEC START

*OPT 4,3

This sets the 'auto-start option' of the current default volume to be EXEC. (For

discs in single density format there is only one volume on each surface of the

disc.) What this means is that now, whenever you press SHIFT and BREAK keys

together, releasing the SHIFT key first, and the default volume is the same as the

volume written to above, and the current disc is in drive 0, then the file !BOOT will

be EXECed.

Text files can also be used for manipulating BASIC program files. Chapter 37 of

the BBC User Guide shows two ways of merging two BASIC programs. The first

uses the command *SPOOL, which sends all screen output to a file as well. The

other, rather confusingly, uses the *LOAD command, which loads files directly into

memory. Normally you should use the BASIC statement LOAD to load BASIC

program files into memory.

Ambiguous File Specifications

An ambiguous file specification is the same as a normal, unambiguous, file

specification, with two extra possibilities.

The character '#' can be used instead of the directory name, and/or instead of one

or more characters in the file name. It represents 'any character'.

The character '*' can be used instead of the directory name, and/or instead of the

last characters of the file name. It represents 'any sequence of characters'.

So the ambiguous file specification J### represents any file in the default

directory with a 4-character filename starting with 'J', and *JI* represents any file in

the default volume with a filename of 2 or more characters, starting with 'JI'.

Many filing system commands accept ambiguous file specifications, and the

interpretation is always 'perform the command action for all the files which match

the specification'.

>*BUILD NIMZO

1 Wherein lies the beauty of 3 P-K5. ?

2 Why is this move strong?

3 The answer is as simple as it is astonishing.

4 The move is strong because it is weak!

>*BUILD START

1 -TV 0,1

2 -FX 6,0

3 *FX 12,3

4 -DIR0

Displaying Catalogues

The *CAT command lists all the entry names in a volume catalogue, together with

information about the volume and the disc. It requires a volume to be specified:

* CAT

will display the catalogue of the default volume, whereas

*CAT 2

will display the catalogue of the default volume on drive 2.

The *INFO command displays the byte length and the load and execution

addresses of all the files matching an ambiguous file specification. Thus:

*INFO * . *

lists the attributes of all the files in the default volume.

Copying Files

When the file START was renamed to !BOOT above, only the catalogue entry was

changed to show the new name. To move the file to another volume or disc, or to

make a second copy of it, one of the filing system copying commands must be

used.

All the filing system copy commands will replace existing files of the same name,

and they all use memory as a buffer while copying files, so you will lose the

current program if you have not first SAVEd it.

The *COPY command makes a copy of a file to a different volume (a different drive

for single density) with the same entry name. So:

*COPY 0 1 f.fred

creates a file A f.fred on the lower drive from the file :0.f.fred on the upper drive.The

command syntax requires a source and target volume, and the entry name of the

source file which will be given to the target file.

If the source and target drives are the same, *COPY assumes that the files are on

different physical discs, and alternately asks for the source and target discs to be

loaded into the drive. This is useful when you have only one drive and want to copy

from one disc to another.

A powerful feature of *COPY is that it will copy more than one file at a time, if an

ambiguous file specification is given.

-COPY 1 0 ##2

will copy all files with the 3-character file names ending with '2' in the default

directory on drive 1 to the default volume on drive 0.

-COPY 0 2 -.

will copy all files from the default volume on drive 0 to the default volume on drive

Earlier the inherent vulnerability of data on floppy discs was pointed out. To protect

your valuable programs and data, you should take frequent copies of all your

discs, and keep copies well away from the masters and the computer.

The simplest way to do this is to use *BACKUP, which makes an exact copy of a

complete disc. Thus

-BACKUP 0 1

copies the disc in drive Q to that in drive 1. The target disc must already have been

formatted to the same density and number of tracks as the source disc, and any

information on it will be overwritten.

e, you can still use *BACKUP:

With only one driv

-BACKUP 0 0

directs the user to alternately insert source and target discs, just like *COPY.

Note that *BACKUP uses all available memory as a buffer, and you will lose your

current program if you have not previously saved it. If you are performing a

*BACKUP on a single drive system, the number of times you will be asked to

swap the source and target discs will depend upon the amount of free memory.

You are advised to select screen mode 7, which provides the maximum free

memory, and hence the least number of disc swaps.

Deleting Files

The converse of copying files is deleting them. The *DELETE command will

delete a single file, providing its lock is not on (*ACCESS is used to manipulate

file locks).

*WIPE and *DESTROY both accept an ambiguous file specification. *WIPE asks

the user if each matching unlocked file is to be deleted, whereas 'DESTROY lists

all the matches and asks the user if they should all be deleted or not.

5 Commands

The commands described in this section all relate to the manipulation of discs

and disc files, but they fall into three categories: operating system commands,

filing system commands and utility commands.

Operating system (OS) commands are available on all BBC computers, and

under any filing system. However, the interpretation of the command is supported

by the active filing system and therefore may vary depending on which filing

system is active. Thus the *CAT command is an operating system command

which is interpreted somewhat differently by a disc filing system from the tape

filing system.

Filing system (FS) commands are supported by the disc filing system, and are

specific to the disc operations performed by the disc filing system. They are

unlikely to be meaningful, or to be interpreted in the same way, when another filing

system is active. Thus *DESTROY is a disc filing system command which is

meaningless to the tape filing system.

Utility commands are supported by the disc filing system, but will function correctly

whatever fillng system is active. Thus * LlST is a disc fillng system utility which can

be used to list the contents of a disc or a tape text file.

The syntax of the commands is described in a similar style to that used in the BBC

User Guide (see p.199). Unlike BASIC, however, the disc filing systems do not

distinguish between upper-case and lower-case letters. Thus *DELETE fred and

*delete FRED are interpreted as the same.

All commands are of the form:

* <command> {<parameter>}

<command> is from three to seven characters. Usually a command may be

abbreviated to a leading substring followed by a full stop. How short the substring

may be will depend on what other commands might share the same abbreviation.

Thus *DRIVE can be abbreviated to *DRIV. or *DRI. or *DR., but not to *D. which

would be interpreted as *DISC.

For filing system commands there is an additional complication in that any

sideways ROMs fitted to the BBC will be given the chance to service the

abbreviated command before the filing system. Therefore, the shortest

abbreviation given with each command may not be appropriate for your BBC.

Each parameter must be preceded by at least one space, and should not contain

embedded spaces except within string contents. Some syntactic

items that occur in the parameters of several commands are defined here.

<drv>

<drvsp>

<sch>

<dir>

<dirsp>

<fi1e>

<entsp>

<fsp>

<asch>

<adir>

<afi1e>

<aentsp>

<afsp>

drive name

drive spec

spec char

directory name

directory spec

fi1e name

entry spec

fi1e spec

ambiguous

spec char

dir . name

fi1e name

entry spec

fi1e spec

0 | 1 | 2 | 3

[ : ] [<drv>]

Any character but

<sch>

<drvsp> [<dir>]

{<sch>}x7

[<dir>.]<file>

<drvsp> <entsp>

When any part of a drive or directory spec is omitted, the corresponding current

default is substituted. Thus if the current default drive number is 1 ' and the current

default directory is $, then the file spec JOE specifies the file A.$.JOE.

*ACCESS <afsp> [L]

Abbreviation: *A.

Type: FS

If the -L- is included, all files matching the ambiguous file spec are locked. If the -L

is omitted, all files matching the ambiguous file spec are unlocked.

A locked file cannot be deleted, overwritten, or written to until the file is unlocked.

The *CAT and *INFO commands display whether a file is locked or not.

Example

>*ACCESS A.TEST L

locks the file A.TEST

>*ACCESS $.*

<sch> | #

<asch> | *

{<asch>}x7 1 {<asch>}x6

[<adir>.] <afile>

<drvsp> <aentsp>