Spectrum CP/M Plus + Mallard BASIC

Your Sinclair

Phil South

RAGE HARD! More hard software for Phil South to write home about, as he encounters not only a new Basic for the Plus 3 but also a whole new language. Locomotive Software [redacted] This month, before we get into doing some tricky little hardware things again, I thought we'd cover just one last bit of software. This is a very special disk for the Spectrum Plus 3, which turns your unassuming Speccy into not one but TWO new computers. Included in the package is Locomotive Software's Mallard Basic, a new version of Basic (surprise!), and CP/M Plus, a natty version of Digital Research's CP/M language (Note: interesting fact that CP/M stands for Control Program for Microcomputers!). Now then, people are always pretending to turn the Spectrum into a so-called 'serious' machine, so how does this obviously technical package took in the light of reality? Pretty flippin' good actually. Although the idea of turning my nice colourful Plus 3 into a monochrome CP/M machine filled me with dread, it's actually a rinky idea. I can now run programs for the Amstrad PCW and CPC machines on my Spectrum! Which opens up a whole new world of serious computing I can tell you, with a torrent of professional spreadsheeting and databasing programs at my disposal. There's games too, not the sort you'd find on the old Speccy in ordinary circumstances, but games nonetheless. CP/M PLUS CP/M is one of the most widely used operating systems in the world, apart from a thing called MS-DOS. If you don't know what an operating system is, then let me explain. An operating system is there in the computer to run programs and organise your data. There are lots of interesting things you can do, like telling a series of programs to execute one after the other, or telling a file to take its data from another file, or even from another computer down the phone line. Basically, your Spectrum becomes a blank sheet of paper, on which you can write anything you like, or make it become any kind of computer you need. This all sounds pretty heady stuff, but what does it mean in the real world? Before you run anything in CP/M, you've got to load the CP/M startup disk. You do this by simply slapping the system disk into the internal drive and pressing ENTER, to select the loader option on the Plus 3's starter menu. The operating system toads up automatically and presents you with the standard CP/M prompt: A* This tells you that the computer is ready to accept a command in CP/M, and that the current drive is drive A, or the internal drive. Each drive has a number where you assign to logical device names like a: or t: for drive A or Tape. (Notice the trailing colons or symbols. These indicate a logical device name). The same goes for CP/M. Oh, by the way, I was well wrong about this version of CP/M being in black and white. You can use all the colours that the Speccy can produce, but only two at a time. The other interesting thing about the screen display is that most CP/M programs run on machines with a 24X80 display. So to help you run other people's programs on your Speccy there are two alternate display modes to try. The first is a 24X51 mode, which prints up the screen in smaller characters, or the 24X80 mode, which gives you the full display in two overlapping slices. Also included with the disk are some utilities, which perform all kinds of interesting functions for you. Like LANGUAGE, a command which changes the character set to any international language, such as French, German, Danish or Swedish. ST SERIAL allows you to configure the serial port to do anything you like, and before you say it, YES, you can use the system for comms work (Even better than that, Spectre Communications has put a special offer coupon inside for its compatible comms package). There are also ways to define keys to do certain keystrokes for you, which could, for example, save you time in programs like Wordstar*, where you have to remember a load of control codes to format your documents. Now then, about running all this interesting software for other computers like the PCW and CPC ranges. Yes, you can run them, but they may not always do what you expect. They might not control the screen and the printer properly, and all kinds of other problems might befall you. So it's advisable to 'install' all software for use on the Plus 3. Don't panic, there is a special installation program which converts programs to work in the Plus 3 environment on the disk. Huh! And you thought you'd get away with just zapping a PCW disk in the drive and booting it up. eh? So all this is very well, but is it art? I ask myself. As an environment to work in, CP/M Plus is as good as most OSs and as a platform to launch interesting programs onto an unsuspecting world, it has no substitute in the Speccy community. MALLARD BASIC Basic is my own preferred language to get things done. Look, I know machine code is fast, and I'm sure that after a while learning C or Pascal I could turn the Speccy on a dime. But I've been programming in Basic for over 10 years now, and I think I'm just starting to become an expert. Speccy Basic was a good tool for getting the Speccy to show off what a spanky little colour computer it was, but for maths and business applications you could just forget it. You had to write these types of programs in machine code if you wanted to get the best out of your Speccy. Until now, you had to look a long way beyond the Spectrum Basic to get sleek, arithmetically fast programs. In short, you were looking at 'serious computers' (it's that word again!) But it's true. If you wanted to do something in Speccy Basic like, for example, calculate the number of stars above the horizon, plot their positions or draw a starmap, you would be greyer than my dad's dog before the first pixels began picking their weary way onto the screen. But now here's Mallard Basic, a program which runs under CP/M (which is kinda lucky since it appears on the CP/M Plus disk) and produces very favourable benchmarked results. Take a look at the comparison using the PCW standard benchmark programs: BENCHMARK 1 Mallard: 0.76 Plus 3 Basic: 6.46 BENCHMARK 2 Mallard: 2.92 Plus 3 Basic: 13.2 BENCHMARK 3 Mallard: 7.98 Plus 3 Basic: 24.7 BENCHMARK 4 Mallard: 8.23 Plus 3 Basic: 20.3 BENCHMARK 5 Mallard: 8.94 Plus 3 Basic: 27.5 BENCHMARK 6 Mallard: 15.6 Plus 3 Basic: 68.9 BENCHMARK 7 Mallard: 24.8 Plus 3 Basic: 102.9 BENCHMARK 8 Mallard: 28.9 Plus 3 Basic: 246.9 So, depending on the problem you're setting the computer, it could be running up to five times faster than the same program running on Plus 3 Basic! The other good feature about Mallard Basic is that it's a disk based interpreter, so it has some features which would not be available if it had to be resident in memory all the time. One of the key advantages of programs written in Mallard Basic, is that unlike Speccy Basic they can be moved across to a range of other computers, with little or no re-writing. This means you can write a program for any computer supporting Microsoft Basic, and it will run almost as it is. Alright, so the emphasis is on file handling and data processing, but this is it's advantage rather than a minus point. It's fast because it doesn't have any truck with all those pretty colour graphics that S Basic handles soooo easily. For those of you with a home business, you can write your own application programs with ease, and because of some unique facilities of Mallard Basic, allowing you to index data stored in a file, and automatically keep this data in alphabetical order. AND SO TO BED... This is a first rate piece of software. I've not seen such a well presented and powerful program for a very long time. The program works flawlessly, and the manual is beautifully laid out and easy to read, giving you access at once to the fabulously complex and powerful facilities the program offers No wading through yards of dry text. It's roll up your sleeves and get dirty time. If you're a hacker, like me, and I mean this in the old fashioned sense of the word, you'll love CP/M Plus. And for the asking price, I don't see how anyone who calls himself a serious Spectrum user can refuse. It's worth much more, so snap it up before Locomotive software changes its mind!

Crash

Simon N Goodwin

(Simon N Goodwin owns the copyright to this review. Please visit http://simon.mooli.org.uk to find original articles and updates, much new material and his contact details.) CP/M EMANCIPATION Despite its success in the specialist games market. the Spectrum has always been a general-purpose computer. Until recently it has been handicapped by an obscure operating system, no standard disks and a limited home TV display resolution. Locomotive Software have addressed all three of these problems with the launch of CP/M Plus for the +3. CP/M HISTORY When micros first appeared, models were all totally incompatible, like game machines today. After a while people decided it was a waste to rewrite programs for every new machine, so they dug out a program written in 1974 that would control disks and a simple display on ANY computer with an 8080 processor, or its souped-up successor the Z80. The program was called Control Program/Monitor, or CP/M for short. CP/M was important because it mean that programs could be written once and work on lots of different machines without changes. All the machine-specific bits were handled by calling the control program. This was a bit slow and restrictive - it ruled out graphics and sound - but it was worth it, because thousands of CP/M programs were written - programming tools, business software, and text games like adventures. Many programs are available at just the cost of a disk and duplication - just a few pounds-from legal 'public domain' software libraries like PD-SIG (Tel: 0896 63298). SPECTRUM CP/M Spectrum CP/M only runs on the +3. It consists of a single three inch disk, brimful with 346K of files on both sides, and a hefty manual. It loads from the +3 'loader' option in about ten seconds, plus another ten while it automatically configures the serial port and an 111( RAM disk (drive C). Once CP/M is loaded you have about 81K of fast memory free for programs, with no need for 'paging'. Usually on a +3 the screen and ROM mean you only have about 40K free in one space, plus a 64K RAM disk. In CP/M up to 15K of otherwise unused memory can work as a fast but small simulated disk - useful when copying small files with only one drive. The rest of the 128K contains the code of CP/M. which runs entirely independently of the Spectrum ROM. CP/M COMMANDS Spectrum CP/M Plus has 37 standard commands, but there's no maximum - the package includes facilities to make your own commands, in BASIC, machine code or by chaining together existing ones. If you type a word CP/M doesn't know, it automatically looks for a file of that name and either executes it - if it's a program or reads commands from it as if you typed them - if the file contains text. This simple scheme is very powerful. +3 CP/M initially recognises 15 'housekeeping' commands. The simplest is TYPE, which shows a named file on the screen, waiting for a key between pages. You enter DIR to find the names of disk files. DIR takes about 3.5 seconds to read and display a directory of 27 files - plus an extra eight seconds if you've just changed the disk, and the computer needs to update its record of the disk structure. DIR (SIZE) uses the separate DIR utility program, and takes nine seconds to load that 15K program, read the same directory, sort it into alphabetical order and display it over 31 lines. DIR work on +3 DOS disks, but TYPE - like most commands - can only decipher the data on CP/M disks. It just plaintively prints PLUS3DOS if you ask it to look at a file created by +3 BASIC. SHOW tells you the amount of space in a drive. DATE lets you read and set the date and time, used to mark files. The rather rudimentary +3 hardware means that the clock loses time when the disk is accessed. The date reverts to Christmas 1982 whenever you reset the system. ERASE and RENAME let you remove files from a disk or change their names. SET can protect a file from ERASE. Names can include 'wildcard' characters, as in +3 DOS, so you can use one command to process several files with similar names. DISCKIT copies disks. It takes about two minutes to copy a 173K disk on a single drive computer - a minute to read and write the data, plus another minute for you to swap the disks back and forth eight times. PIP is the rather clumsy 'Peripheral Interchange Program'. It lets you copy files back and forth between disks, the screen, serial and parallel ports - but not MIDI, which did not exist when CP/M was designed. OTHER COMMANDS There are ten configuration commands. For example, the PALLETTE command lets you set the foreground and background colours; the default is white on blue. The other 12 commands are only briefly mentioned in the manual - they are 'advanced programming tools' - well, they were when CP/M was invented, but today they seem a bit crude. ED is the standard CP/M line editor, and is horrible; not much better is RPED, a screen-editor for up to 200 fines of text, written by Amstrad in protected BASIC. It's simple to use but very rudimentary, and won't let you copy or move information between lines. RPED is alright if you just want to write a few command-files, but it's not much good for programming. You get two assemblers - for the 8080 processor rather than the Z80 - and can try them out by assembling the well-commented RAM disk source code provided. All the 8080 instructions run on the Z80, but they have different mnemonic names so the source looks pretty odd! To make things even stranger, the program uses Z80 codes which the 8080 couldn't handle, and these are 'defined' as bytes and words in the program. Even so, it's an interesting example. KEYBOARD Like ZX BASIC, CP/M is usually controlled by typing commands at the keyboard. However, CP/M lets you change the characters produced by every key, and there's a massive character set, including foreign accents and loads of weird squiggles. Some commands use the square and curly brackets, which Amstrad didn't mark on the keyboard. Locomotive have positioned these sensibly on unused ;pairs of symbol-shifted keys. BREAK is the equivalent of CP/M's 'Escape'. and EDIT usefully recalls the last list entered for editing - try doing that in GEM or on an Apple Mac! EXTEND works as a 'control' key so, for example, Control S and Control Q stop and start scrolling, the TRUE and INVERSE VIDEO keys give the same effect more conveniently. You can divert input and output to any device with commands. If you've got a printer connected, Extend P is a convenient way to copy all display output to it. Keys repeat, without over-running, when you hold them down for a while, but there's no key-click, and on this early review version the cursor disappeared annoyingly when the arrow keys were held down. At first, Locomotive Software excused this on the grounds that they tried to make the screen display fast, and no-one complained about this bug on earlier Amstrad CP/M machines. Since then, Locomotive have relented and the latest versions of CP/M do not have this cursor problem. You can 'type ahead' while commands are running. Sometimes the characters you enter get lost, but usually they appear on the next command-line. The effect depends on what the computer is doing, but it's a useful feature when you get used to its quirks. The line editor lets you move back and forth through up to 239 characters of command and 'parameters, adding and deleting at will. Unfortunately you can't edit characters unless they're on the same display line as the cursor. MALLARD BASIC Mallard BASIC is a 28K code file, it loads from the CP/M command level in about 5 seconds, leaving just over 30K for file-buffers, variables and your program. Mallard BASIC is aimed at serious programmers, and is very like IBM's GW BASIC or Microsoft's MBASIC. You enter program lines of up to 255 characters, but the syntax isn't checked at once, as it would be in ZX BASIC, if a mistake is found when the line is executed, you are then thrown into the line editor. The BASIC editor works like the CP/M command editor, with extra tricks to move up and down between screen lines, search for a specific character, and delete or overwrite chunks of text. You must tell it the width of the screen line with the WIDTH command before it will work in 32-column or 80-column mode, or strange things can happen! In BASIC, the keyboard functions are sadly inconsistent with the CP/M command level - a common problem with early operating systems where every program has its own conventions. EXTEND A works like EDIT in CP/M, recalling the last line as long as you have not yet started to enter a new command. BREAK is ignored, but EXTEND C will stop your program unless you've protected against it. Control G is the only way to make a sound, unless you resort to OUT instructions to control the speaker directly. Type Control G in BASIC, to hear a simple 'beep' sound. In CP/M this only makes a sound when you print the character - not when you type it. Display control is rudimentary, with no graphics commands at all. You have to print control characters to change colours, move the cursor or clear the screen. In ZX BASIC you'd type CLS, but in Locomotive BASIC you must use terminal control codes: PRINT CHR$(27); "H"; CHR$(27);"J" . This gibberish means your programs will work on most other CP/M machines. and suits the IBM PC or Amstrad PCW, both of which run Mallard BASIC and use the same control codes. Mallard BASIC allows four different data-types. Integers - whole numbers between -32768 and 32767 - are more concise and slightly faster than other numeric types and are particularly useful for array subscripts. Maths functions like SIN and LOG use the default seven-digit floating point 'single precision', and real number-crunchers can add, subtract, multiply and divide 16-digit 'double precision' numbers. You pay for the precision in time and memory. Variable names can be as long as you like, but strings are limited to 255 characters, unlike ZX BASIC. Locomotive BASIC has the big advantage that you don't have to tell the system the maximum length of string array variables. Like Microsoft and ZX BASIC, but unlike more modern BASICs, Mallard BASIC is not well-suited to structured programming. There's IF... THEN... ELSE, which can be nested but must be on one line, and WHILE... WEND for loops that start with a test. Unlike +3 BASIC, Mallard has proper file-handling and lets you trap errors, mask the bits of integer values, search strings and trace the current line-number. Overall it's much more like Fortran than Pascal, although when it comes to program development it has the edge over both those languages in that it is interpreted, and you can edit and test the code very quickly. Sadly, there's no compiler aVallable. Locomotive say, unconvincingly, that their interpreter is as fast as other people's compilers. Methinks they expect people to use other languages if they need the speed of compiled code. Three file-handling schemes give you most of the traditional data-processing options, including sophisticated ISAM (Indexed Sequential Access Method) files, usually only found on big multi-user systems. You can manipulate normal text files, printing lines then reading them back, one by one, in order. Alternatively you can use 'random access', dividing a preset file space into fixed-sized sections, called 'records'. Later you can tell the system to GET or PUT collections of text and numbers in any section in the file, just by supplying the appropriate record number. ISAM files come in two parts - one file contains the data, as in a random file, and another file, the 'index', contains labels or 'keys' used to access the data. You no longer need slot numbers, as you can associate any number of keys - strings of up to 31 characters - with any record in the data file. You can use up to eight independent indices with one file. ISAM files can save a lot of work, but it takes a while to get the hang of them and they tend to be wasteful of disk space. You can't write a shoot 'em up in Mallard BASIC, but it's still a valuable addition to the Spectrum programmer's armoury. CAN IT BE TRUE? CP/M is no use unless the implementation is genuinely compatible with the thousands of programs available for the system. Spectrum CP/M has quirks, as you might expect, but it runs most CP/M programs. The disks, at 173K, are small by modern standards, but many CP/M machines had even smaller drives - 88K was not unknown! CP/M software is often sold on 5.25 inch disks, but conversion is not too much of a problem, as lots of firms and interest groups can convert CP/M stuff for CPC and PCW computer users with three inch drives. Spectrum CP/M seems to work fine with 173K Amstrad disks. Pro Pascal and Pro Fortran, for the PCW 8256, just plugged in and worked, although they were short of space for files on my single-drive +3. Most CP/M systems had two drives. The +3 can run a plug-in drive B, but most people won't want to spend that much. Locomotive provide useful two-drive emulation on drive A - the system lets you use two disks in one drive, telling you when to swap them. But beware: this can get very tedious if the program is copying a file, one line at a time, from one disk to another! An optional status line, at the bottom of the screen, says which disk should be in the drive at any time. Spectrum CP/M can display a maximum of 51 characters per line, or 32 per line with full colour control. Most CP/M packages expect an 80-column display. To get around this, Locomotive provide a simulated 80-column mode, showing 80 columns in two overlapping 51-column sections. There's a marker on the status line to show which side you're on. Flicking back and forth can follow the cursor, or be manually controlled. Either way it works with most packages, but makes some very hard to use. Text output is slow: screen updates are about a third the Speed of ZX BASIC, in both sizes: scrolling is about 60% of ZX BASIC speed in 51-column mode, but - bizarrely - only 44% of Sinclair's speed when scrolling a 32-column display. CP/M uses two characters to mark the end of a line. Some printers only expect one, and give double-space output when you use them from CP/M. You can cure this by adjusting a switch inside your printer, unless you've got a really cheap and nasty model. You must use the serial or parallel ports - ZX and Alphacom printers won't work at all from CP/M. DOCUMENTATION The manual is in three sections: the first 100 A5 pages explain how you use the system - entering and editing commands, performing 'housekeeping' tasks such as copying and editing files and disks, and 'configuration' - customising the system to your favourite key-layout, language or printer. This part of the manual shows the benefits of CP/M's 14-year life and Locomotive's long experience of the system - it's clearly written, although a long and wordy read for anyone who doesn't like books. It's packed with little comments that show that the authors have actually done what they are writing about. The next section, 160 pages long, covers Mallard BASIC. It's a tutorial introduction to the language - incomplete but quite a good 'taster'. The tutorial is no substitute for a proper reference guide, so the £10 Mallard BASIC Reference Manual is probably a vital purchase if you're serious. It starts with a similar tutorial, followed by an extra 300-odd pages methinks there's a frustrated blockbuster novelist at Locomotive Software. The CP/M manual ends with over 100 pages of appendices, covering disk contents, keywords, machine code system calls, detailed device specifications and error messages. My pre-release copy lacked an index, which Locomotive will add in the final version. They recommend that techies buy the Digital Research CP/M Plus Manual, for further information about the programming tools and the design of the system. VERDICT At £30 for CP/M Plus, utilities, and Locomotive BASIC, this package is a bargain if you're at all interested in computers for their own sake. CP/M Plus transforms the +3 from an ingenious but ageing games machine into an old-fashioned but useful non-specific computer SYSTEM. Like many others, I've found such systems a fascinating kind of general-purpose tool and toy to have around the house. It's fun, but it takes hundreds of hours to learn your way around such a system, and not everyone can be bothered. Even if you don't want to be a hacker, you can be a 'power user' with CP/M, using whatever parts of it appear to run a customised computer system for work, business or fun. Suddenly there's more to be read in computer magazines, because you can run all the CP/M packages reviewed in CRASH, Amstrad magazines and multi-format titles like Computer Shopper.