Scor­pio News

This article briefly discusses the software available to improve CP/M and suggests some simple CBIOS modifications that the user can carry out, that will give additional system flexibility. These modifications apply to CP/M Version 2.

Only a day of two ago an acquaintance who is still using NASDOS and POLYDOS rang me and said ‘You use CP/M don’t you – I have heard that its as friendly as [expletive deleted] so I don’t know whether to upgrade’. My reply was to the effect that since he was a Nasbus/​80-BUS user, he could progress to what is probably one of the best implementations of CP/M available.

Certainly, to the average user of microcomputers, the mouse and window approach as exemplified in the Mackintoeh is very attractive and easy to use. However I think that moat readers of this newsletter are probably more aware of the inner workings of the machine than the average user, and would find the relative inaccessibility of the modern machine extremely frustrating.

The NASBUS/​80BUS system is geared to the engineer, scientist or enthusiast who needs to be able to alter his hardware systems and associated software. The system may look a little old fashioned when compared with the sleek plastic machines around now, but it lives on whilst many others fall by the wayside. The enormous range of available CP/M software (and our investment in it), and the flexibility of systems like ours make it worthwhile to stay in the 8 Bit world.

Of course standard CP/M is rather unfriendly. It evolved in a world where TTY terminals, Tape readers and Punches were still common, this is still reflected in software like ED.COM and MBASIC.COM, where the line editing features are truly as unfriendly as a hungry wolf. Fortunately, it is not necessary to remain locked in the embraces of standard CP/M. There is a lot of software around, much of it in the public domain, that can transform CP/M into a much more sophisticated system, and the various CBIOS’s available on Nasbus/​80-BUS systems make system extremely friendly when compared to many other system. Above all, it is the ‘ON SCREEN’ EDIT feature, starting back in the good old Nascom days, that is so useful.

CP/M consists of three modules, namely the CCP, the BDOS and the BIOS. These modules are much more fully described in the CP/M manuals, various books and some of the references in appendix 2.

The CCP (Console Command Processor) is the part of CP/M that sits showing the A> prompt and waits for your command. It is 2k bytes long.

The BDOS (Basic Disk Operating System) is the interface between the CCP or currently running program and the BIOS. It is 3.5k bytes long.

The BIOS or CBIOS (Customized Basic Input Output System) holds the software that actually controls the system hardware. The CBIOS therefore varies from machine to machine. It can be any length up to about 4k Bytes long. Obviously the longer the CBIOS, the better the system (ought to be) in terms of hardware support and user friendliness.

It is not intended to describe in any detail the implementation or modification of advanced module, which is usually well described in any accompanying documentation, but merely to describe what is available, or to indicate the main features. Readers who wish toobtain a more detailed understanding of CP/M or modifying it may find some some assistance in articles referred to in Appendix 2.