| ★ APPLICATIONS ★ PROGRAMMATION ★ HISOFT DEVPAC80 V2 ★ |
Devpac80 version 2 (Amstrad Action) | HISOFT DEVPAC80 V2 (Popular Computing Weekly) | DEVPAC80 v2 (Amstrad Computer User) | HISOFT DEVPAC80 V2 (Aktueller Software Markt) |
THE ASSEMBLER'S DREAM Tony Kendle reviews Devpac 2, the latest and most eagerly awaited of the “new wave” assembly language development systems. But does it live up to expectations? Regular readers will be aware that there is a veritable renaissance underway in the field of assembly language development systems. Suddenly the old reliable standards, familiar in zillions of extremely average programs that have been churned out by almost every software company you could name, have been left behind. The first of the 'new wave' was Laser Genius, written by Oasis for the Spectrum, Commodore 64 and Amstrad CPC. More recently there was Maxam II by Arnor for the CPC 6128 and Amstrad PCW. However, the one that has been most eagerly awaited by programmers everywhere has to be the upgrade of the evergreen Devpac, the tool that has bred a generation of Z80 machine code experts from the earliest days of the Spectrum. There can be no disputing that HiSoft is the master of almost every different programming language available on home computers, a sort of British Borland. More The result of its work, Devpac 2, is a programmer's joy, powerful, streamlined and easy to use. It is unquestionably the best thing available on most CP/M computers - Tatung Finstein and MSX owners in particular take note, this is the assembler package for those machines. On the Amstrad range there is more competition from Maxam II, and it was the Amstrad version of Devpac 2 which was sent for review, as much as anything because the PCW, with its fast memory drive is getting a reputation as an excellent program development tool. Maxam scores through having its own inbuilt file and disc copy and disc formatting routines which make it a complete self-contained package, although as we will see later this also causes problems. Devpac comes with a less comprehensive suite of Hisoft disc utilities (including a file conversion routine for CPC AMSDOS Devpac files) which allow much more flexible file copying and erasing, etc, than can be achieved with the standard commands. The original Dev-pac80 files are also included for anyone who wants to gain familiarity with the new modules one by one. The Maxam editor has the merit of being developed from the superb full featured word processor Protext, and therefore is very much better than anything seen before in assembler packages. Devpac's new editor has less features, but conversely the ones that are there are more closely integrated with the other parts of the development package such as a menu driven system that will call up the assembler and monitor and assemble the current edited file, or one stored on disc. The assembler can return direct to the editor once assembly is completed or aborted - it may not seem much but such small points of logisitics can take on inflated proportions when you are mid-way through an enormous programming project, and this feature is actually very rare. Best of all is the ability of the program to remember where errors were found on the first or second assembly pass, and return the user direct to the offending line in the source file with suggestions for what is wrong. Devpac's editor works with a wide selection of Wordstar compatible controls. For those who cannot abide Wordstar these control keys can be re-defined, but as it stands it will appeal to a myriad of die-hard programmers whose fingers are irredeemably locked into configurations such as Control-KD. Like Maxam, files much larger than can fit in the spare memory can be edited and assembled by using the disc as virtual memory. The Devpac assembler largely conforms to the usual Zilog standards but also has been designed to work with files produced by the Microsoft M80 assembler. The internal format of the files it produces are much more standard than Maxam's. Notable features include conditional assembly, a wide range of arithmetical and logical operators, multiple line comments and excellent printer control. Lines of assembly can be directly typed in at the keyboard and automatically inserted at the beginning, or elsewhere, into a disc file undergoing asssembly. This is designed to let you add options to a program which you want to use for test purposes without having to alter the original source code. Unlike many assemblers, Devpac 2 can be installed so that it does not abort on the first pass if errors are found. This allows any second pass errors to be found at the same time ready for editing or listing to the printer. The assembly process can be tested without an object code being produced. Symbol files can be passed to the monitor, or any other standard CP/M program, for symbolic dissassembly. A very nice touch is an extension of the CP/M plus virtual discing feature whereby different files can be named as being read from, or written to, different discs by specifying them as being on drive, B, C, D, etc, regardless of how many drives you actually do have fitted. As well as COM programs, Devpac produces highly standard CP/M REL (relocatable) object code files. These can then be used by any CP/M linker including those usually supplied on the CP/M system disc, and can also be linked to the code produced by other languages such as Pascal or C. Extremely powerful control is given over such files providing relative and absolute symbols and public symbol definitions, etc. Devpac can be used under either CP/M 2.2 or CP/M Plus and so memory bank switching commands are supported if the program senses that it is running in the latter environment. Devpac has always been noted for the quality of its macro handling, but this has now been expanded in various ways to allow the user to be able to define their own pseudo-instruction extensions to the standard Z80 opcodes. The monitor represents one of the most important advances over the old version. It can of course be used as a symbolic debugger and the disassembly can then be written to a disc file ready for editing etc. On the large PCW screen a very useful display of information can be presented, 29 lines of disassembly, a command line and an 80 byte hex and Ascii memory display. A range of the standard monitor commands are available such as fill memory range, compare memory with a given entry, set the memory bank, search for a given mnemonic etc. All of these are extended by a powerful range of arithmetic and logical operators for use in your expressions. Several types of breakpoint exist - hard breakpoints that terminate the code exce-cution when reached, warm boot breaks that trap any attempt by the code to restart CP/M, watchpoints which count the number of times a certain piece of code is executed, and conditional breakpoints that cause a break when a certain condition is met. The most notable aspect is that all of this has been accomplished in just 12K and with the aid of some memory switching you are left with a hefty 54K free for your program files (under CP/M plus). It is something like a third as large as Maxam's monitor which possibly is too user friendly, providing the full range of disc management commands instead of preserving every spare byte of memory for the user. Indeed the whole Devpac package is so compact that all three modules easily fit within the memory disc of an unexpanded PCW. There is no question that Amstrad owners now have two comparable and unprecedented^ good assemblers to choose from. Each has its own strengths, but in the end most people are likely to vote with their pocket. It is inevitable that the vast majority of potential customers already have assemblers of some sort. Whilst anyone with an ounce of sense will see the value of upgrading to one of these excellent releases it is hard to imagine that they will ignore the fact that Devpac is almost half the price of Maxam II. PCW |
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