The User Guide provided by Acorn to go with the Master 512 includes very little about many of the support and utility programs on the supplied DOS-Plus boot disk. Most of them are described quite adequately though in the two books produced by Dabs Press, namely the Master 512 User Guide by Chris Snee and the Master 512 Technical Guide by Robin Burton.
However, on the disk which goes with Version 2.1 of DOS-Plus there is one program for which the function is not described anywhere. This is the file called FIDDLOAD.COM. To be fair, it is referred to in the Acorn User Guide, and Chris Snee's book does mention it, but simply to state that it has something to do with using installable device drivers. No practical details are given as to how to use it.
I found it irritating to have a file on the system disk about which I knew nothing. It might turn out to be useful! But how could I use it? I decided to examine FIDDLOAD carefully to try and find out what it was really for. This is a summary of my investigation. FIDDLOAD does not, in fact, turn out to be the most useful of the DOS-Plus support programs! Read on, though, if you would like to know what it does, and why most users would be better off without it.
FIDDLOAD has been included on the boot disk because of a difference between DOS-Plus and MS-DOS. When an MS-DOS PC boots up, the system looks for a file called CONFIG.SYS. This file contains information about how DOS is to configure itself. CONFIG.SYS is always a text file, so it can be edited with a word-processor or text-editor. It will contain lines like:
which tell DOS to allow space for up to 30 open files, and to load as a "device driver" a file called "MOUSE.SYS".
DOS-Plus, on the other hand, does not use a CONFIG.SYS file. It has a fixed allowance of open files; it does not use installable device drivers; etc.
What FIDDLOAD does is to cause DOS-Plus to read a CONFIG.SYS file. You do not need to do anything to cause FIDDLOAD to work except to have it present on the disk. If your boot disk contains FIDDLOAD.COM and a file called CONFIG.SYS (both in the root directory) then the contents of CONFIG.SYS will be acted on automatically when the 512 is booted up.
Don't get too excited, though! The way that CONFIG.SYS is acted upon is very limited. You are still stuck with a fixed number of open files, for example. Only four kinds of lines mean anything at all. Other lines are ignored.
The lines that have a meaning are:
|DEVICE = <file-name>|
|This causes an MS-DOS-format device driver to be loaded. Do not expect many of these to work with the 512, however. Device drivers always access the hardware directly, and the Master 512's hardware is quite different from that of a genuine PC compatible. The only drivers that have any hope of working are "pseudo-drivers" which do not refer to anything except normal memory or the screen contents. Nothing else stands a whelk's chance in a supernova. And even with things that might work (like, for example, a RAM-disk program) there are problems. Only a few of the normal device driver entry points exist, and there are bugs. Device drivers are actually of two types, known as "character devices" and "block devices". For character devices only one function (initialization) is supported. More functions are supported for block devices, but these always seem to give an "Out of memory" error, even when there is plenty of memory to play with.|
|COUNTRY = <decimal number>|
|This defines the current country of operation. Acceptable values are: 1 (USA/Canada), 30 (Greece), 31 (Netherlands), 32 (Belgium), 33 (France), 34 (Spain), 39 (Italy), 41 (Switzerland), 44 (U.K. – the default), 45 (Denmark), 46 (Sweden), 47 (Norway), 49 (Germany), 61 (Australia), 358 (Finland), 972 (Israel). Application programs can read this information, and some of them might use it to set up a default currency symbol, for example. If you want to convince yourself that it really does something, then you could try setting COUNTRY=1. Doing a DIR when you have set the machine up like this will give you file times and dates in American format. In practice, though, very few programs do use the country information directly. If they require it at all you will usually need to enter it as a command line parameter or else define it within the program itself.|
|SWITCHAR = <character>|
|This sets the switch character. The switch character is the character used by programs (including COMMAND.COM for internal DOS commands) to identify command line switches (ie options). Its default value is "/" and so, for example, with the DIR command you can use "/W" to give a wide display, or "/P" to give a paged one. This configuration option allows you to change the switch character. However, once again there are serious limitations. Only two characters are valid: "/" (the default) and "-". Also, very few applications take any notice of the specified switch character. Many expect you always to use "/", some insist on "-", others will accept either.|
|LASTDRIVE = <drive letter>|
|This specifies what is supposed to be the number of logical block devices (ie logical disk drives) in the system. The given drive letter must lie between A and P (inclusive)."A" means 1 logical block device, "B" means 2, etc. This is somewhat misleading, though. Master 512 DOS-Plus actually recognizes four block devices (two floppy drives, one hard drive, and a memory disk) and nothing can change this. Despite such reality, the default "number of logical block devices" is 5. The value specified can be read by programs, though I have come across very few that use the information.|
If you have read through all the above, you will probably feel, as I do, that FIDDLOAD.COM is a pretty useless program. However there remains one useful thing you can do with it. That is: Delete it!
If FIDDLOAD.COM is present in the root directory of the boot disk then it will be loaded every time you boot the system and it will then search for a CONFIG.SYS file. If you are booting from a floppy disk this process takes about 5 seconds, assuming no CONFIG.SYS file exists. So if you delete FIDDLOAD.COM from your boot disk, then system boot will take about 5 seconds less time to complete. The improvement is quite noticeable.