8087
8087 = ON
8087 = OFF

A>8087=ON
8087=OFF

(The 8087 does not exist and can't be turned on)

(DR definition only – see notes)

8087 not installed
The 8087 is not installed. Most programs do not require the 8087, but those that do will use it if present, or simply run slower if it is not.

8087 in use
A background program is using the 8087. Do not run another program which requires it.

This command is only included for compatibility with other versions of DOS Plus. As there is no provision for a maths co-processor in the 80186, this command always returns the message:

8087=off            (DOS+ V1.2)

or

8087 not installed  (DOS+ V1.2a/V2.1)

A>ADDMEM=0
Additional Memory Allocation = 0
A>

Allocates all available memory to the foreground EXE program.

A>ADDMEM=333
Additional Memory Allocation = 333
A>

Allocates 333k to the foreground EXE program.

A>ADDMEM
Memory Allocation = 333
A>

Returns the present memory allocation

This command is only included for compatibility. It has no effect, but is recognised to prevent batch files converted from other machines from crashing.

IMPORTANT: Note that what is being simulated in this command is CTRL-BREAK on a PC, not CTRL-BREAK on a BBC micro. The key combination on a PC causes termination of the current program, like ESCAPE in the BBC micro. The same effect can be obtained on a PC by CTRL-C. The equivalent of the BBC's CTRL-BREAK is achieved on a PC by simultaneously pressing CTRL-ALT-DEL. Just to confuse you even further, CTRL-ALT-DEL doesn't function on the Master 512 – to reset the system, press CTRL-BREAK.

C>CD C:\dir1

Change current directory to \dir1.

A>CD dir1\dir2

Change current directory to dir1\dir2.

A>CD ..

Change current directory to parent of current directory.

A>CD ..\..

Change current directory to parent of parent directory.

C>CD A:\dir1

Change the current directory of another drive.

C>CD N:=A:\dir1

Assign floating drive N: to a:\dir1.

A>C:CD
C:\dir1

Display current directory (in this case \dir1).

C>CD A:
A:\

Display current directory of another drive.

A>CLS

Clears the screen and moves the cursor to the top-left corner of the screen and displays the current DOS Plus prompt.

A>COMSIZE
Memory allocation = 0

Displays the current memory allocation.

A>COMSIZE = 0
Memory allocation = 0

Allocate all available memory.

A>COMSIZE = 200
Memory allocation = 200

Allocate 200k to COM files.

COPY {/A}{/B} {d:}<filespec> {/A}{/B}{/S} {+<filespec> {/A}{/B}} ... {<filespec>} {/A}{/B}{/V}

The filespec may be substituted with a device. For example:

     AUX:     CON:     PRN:     NUL:

A>COPY TEXT.DOC B:

Copy the file TEXT.DOC from the current directory on drive A to the current directory on drive B.

A>COPY A:text.doc B:letter.doc

Copy the file text.doc from drive A to drive B, naming the new file on drive B letter.doc.

A>COPY B:text.doc

Copy the file text.doc from drive B to the current directory on the current drive.

A>COPY CON GO.BAT

Copies keyboard input to the file GO.BAT until a CTRL-Z character is typed.

A>COPY text.doc letter.doc

Copies text.doc on drive A to a file called letter.doc, also on drive A.

A>COPY txt1.doc+txt2.doc+txt3.doc b:letter.txt

Copies the three files, txt1.doc, txt2.doc, txt3.doc in sequence from drive A into a single file called letter.txt on drive B.

Never include spaces in a destination file name. There is a bug in DOS Plus (1.2 and 1.2a) such that failure to observe this rule can result in a destination file length of zero, with no error reported. Worse still, if you supply no destination name, DOS Plus first assumes that the destination name is all spaces but then also uses the source name for the destination as normal, setting the file length of the new file to zero before writing to it. If this is the same name as the source, the file by then zero length, is copied to itself, resulting in a zero length file and no error.

If you meant to type

COPY *.EXE *.BAK

but just typed

COPY *.EXE

you would lose all the EXE files in that directory on your disc – permanently! At this stage you do not have a destination file copy, and the source file is lost too!

DATE {dd-mm-yy}

Note that the dash delimiters (-) may be replaced by full stop (.) or back slash (/).

The BBC Master has a real-time battery backed clock (RTC). The DATE command refers to the DOS system clock which is not always the same value as the RTC. The date and time are only read from the RTC (if available) at initialisation.

If the Master 512 is used without an AUTOEXEC.BAT file, initialisation is automatically requested during start-up (see page 14). Manual entry is required. Some third party alternative RTCs, such as Genie Watch (which supports the correct system calls) can also be used, or you could write your own RTC code as a Sideways ROM program on the BBC micro.

A>DEL File.*

Delete all files with the name 'file', on the current drive, but any extension is acceptable.

A>DEL B:*.BAK

Delete all files with the extension BAK, on drive B: but any filename is acceptable.

A>DEL *.*

Delete all files! This will cause the reponse:

Are you sure (Y/N)?

Only if you respond with Y will the operation take place. Any other key aborts the deletion.

Deleting a file only removes the name from the directory. By using the correct method (a disc sector editor, or an appropriate utility) it is possible to recover a deleted file.

DEL does not delete files with access permission set to read-only.

This command is functionally the same as ERASE.

A>DELQ B:*.DOC

Erase all files with the DOC extension in the current directory of drive B. As each filename is presented deletion is queried by:

filename.ext (Y/N)?

Answer Y to delete the file, or N to omit it from the delete operation.

A>DIR

Display the contents of the current directory.

A>DIR *.BAK /W

Display all files with a .BAK extension in the current directory using the wide display format.

A>DIR B:text.doc

Display information about the file text.doc on drive B.

If a DIR command can't find a file which matches the optional file specification the message displayed is:

File not found

The command DIR *.* is the same as DIR without any parameters.

C>ERASE *.BAK

Delete all files with the BAK extension in the current directory, any filename is acceptable.

Be careful with ERASE *.* when using a hard disc. Erasing everything from the root directory will result in the loss of COMMAND.COM, and the system will no longer be bootable from the hard disc.

This command is functionally the same as DEL.

A>ERAQ *.BAK

Erase all files with the BAK extension in the current directory of drive A. As each filename is presented erasure is queried by:

Filename.ext (Y/N)?

Answer Y to delete the file, or N to omit it from the erase operation.

A>MKDIR words

Create a new directory called words, subordinate to the current directory.

A>MKDIR words\letters

Create a directory called letters, subordinate to the directory called words, which must be subordinate to the current directory.

A>PATH C:\DOS;B:\UTILS

Tells DOS Plus to look for commands in the DOS directory on drive C, or the UTILS directory on drive B, if they are not found in the current directory.

When a command is issued, DOS Plus first looks for the command in its table of resident commands. If no such command exists DOS assumes the command to be a transient and next searches the current directory, looking for a filename the same as the command name with an extension of .CMD, .COM, .EXE or.BAT.

If the file is not found DOS next searches all the directories in order, as specified in the PATH command. If the file still cannot be found DOS finally searches the root directory.

If at any stage a file is found it is executed. If no such file could be found DOS reports 'Bad command or filename'.

By convention the transients are placed in a directory called \DOS and this is set in the PATH to be searched for unrecognised commands.

The characters below can be preceded by a $ in the PROMPT command to produce a new systems prompt. They will appear in the order specified, and will cause the following to be included in the new prompt:

The text string must not contain the following characters:

<, >, | or =

A>RENAME text.dta text.txt

Renames the file 'text.dta' to 'text.txt', both within the current directory. Note that the syntax is reversed from the original CP/M command.

If the new name already exists, the file can't be overwritten and an error message is displayed. The command is terminated on error.

The command is very similar to the BBC MOS *RENAME command.

A>RD dir1\dir2

Deletes the directory 'dir2', which is subordinate to 'dir1'.

A>RD B:\temp

Deletes the directory 'temp' from drive B.

A directory can only be deleted if it contains no files or sub-directories (even if these are empty). If you try to remove a directory which is not empty the error message:

Dir. not empty

will result. No alteration is made to the disc.

A>SET
PATH=
COMSPEC=A:\COMMAND.COM
OS=DOSPLUS
VER=1.2
PROMPT=$u$n$g

A>SET COMSPEC=B:\COMMAND.COM

A>SET PROMPT=$p$g

A>SLICE 10

Allocate 10 time units to foreground for every unit allocated to background.

A>SLICE
Foreground time slice = 16

Display current slice value:

Invalid Slice Specification (1- 255)

SLICE has been followed by a number which is not a number between 1 and 255.

System help suggests that time-slicing is on the basis of 16 units. This contrasts with the error message shown above, which suggests that slices may be defined in 255ths.

In fact SLICE does accept values up to 255, but if a value greater than 127 is supplied in 2.1 a subsequent SLICE request (without parameters) shows a corrupted value.

DOS plus allows certain tasks to be run in background mode. The system shares processor time between the main (foreground) task and any background tasks, based on the time-slice set by this command. The default setting is 16, which means that 16 time units are spent executing foreground tasks for every single unit spent on each background task.

A>TIME
Current time is 15:24:07.44
Enter new time:

If no time is entered then the existing time is retained.

The time is set using the 24 hour dock. On a Master TIME is automatically initialised to the value given by the micro's real time clock. The seconds and hundredths are optional when manual amendment is requested, or when booting the system on a micro without an RTC.

See also the notes on page 14, concerning the AUTOEXEC.BAT file

A>TYPE text.doc

Display the file text.doc on the screen.

A>TYPE text.doc /P

Display the file text.doc, pausing at each screenful (24 lines).

The keys CTRL-S and CTRL-Q pause and re-start the TYPE command during execution. CTRL-C abandons the command, and CTRL-P toggles the printer on and off. To print a file use CTRL-P after entering the TYPE command, but before pressing RETURN. At the end of the display, which still echos to the screen, press CTRL-P to disable printer output again.

Unlike MS-DOS, DOS Plus will accept a wildcard argument when typing files, so if you issued TYPE FILE?.DOC and two files existed in the current directory, FILE1.DOC and FILE2.DOC, they would both be typed, in alphabetical filename order, each file's output being preceded by it's name in inverse video.

A>USER
User number=0

Displays the current user number.

A>USER 1
User number=1

Changes the current user number.

VOL A:
Volume in drive A: is MASTER 512

Displays disc volume label as set by the formatting or copying of a disc, or by the transient LABEL. (Version 2.1 only.)