The *MAP command produces a rather cryptic list of the areas of the disc which

are free. If you issue a *MAP command you might get a table like this:

Address : Length

000002 : 00000A

00014A : 000043

0001E3 : 00013D

The list you see may be shorter or longer than this, and the numbers it displays

will certainly be different. Each entry consists of a disc address and the amount

of space free at that location. Both numbers are given in hexadecimal.

The ADFS keeps this free space list automatically, and updates it whenever

files and directories are created and deleted. Because free space is broken up

across the disc it is quite possible for sufficient space to be available to save a

file but for it not to be contiguous on the disc (which is a prerequisite of the file

structure). It may therefore be neccessary, on occasion, to compact the disc

and the computer may warn of this with the 'Compaction required' error.

Compaction shuffles the files around on the disc to close up the free space 'holes'

and leave the largest possible area of contiguous free space.

Just like the *COPY command, *COMPACT makes use of as much shadow

screen memory as possible. When you issue the command:

*COMPACT

the red drive light will glow, and may continue to do so for up to a couple of

minutes. When it goes out, you will find that a *MAP command reveals a few

large chunks of free space on the disc. You can then return to your previous

screen mode and continue with your work.

MOS Filing System commands

What follows is a discussion of some general-purpose commands that the MOS

operating system provides for use with any filing system; in the examples that

follow, use of the ADFS is assumed. These commands provide advanced

facilities which are likely to be employed mainly by experienced computer

users; you should not feel under any obligation to read this information on your

first pass through the Guide.

A note about the ROM Filing System

The reader should be warned that, because of the read-only nature of the ROM

Filing System (RFS), a proportion of what follows is not relevant to its use.

Specifically, the RFS does not implement any commands which attempt to

create or alter files, and thus does not support *SAVE, *SPOOL, *BUILD,

*CREATE or *APPEND.

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