Microdrive Utility System

MICRODRIVE UTILITY SYSTEM


by JB Souter


from Sinclair User, October 1984





EASY ACCESS





Interface 1 and the microdrives have been criticized


frequently as they are difficult to use. J B Souter shows


how to make them flexible friends.








THERE IS GOOD NEWS and bad news for Spectrum owners who have


upgraded their micros by adding the Sinclair Interface 1 and


microdrives. The good news is that several new powerful


commands are available. The bad news is that syntax of those


commands is both unfriendly and unwieldy.





For example, it takes 22 keystrokes, not counting shift


keys, to merge a BASIC program which has a 10 character


filename. Although the Interface 1 contains an RS232 port to


which a serial printer can be connected, the commands "COPY"


and "LLIST" which do screen dump and listing to the ZX


Printer either do not work or require additional commands


first. In the case of "LLIST", a subroutine is required as


follows:





9000 REM: list to printer subroutine, set baud rate first


9010 FORMAT "t" ; baud rate


9020 OPEN #3; "t"


9030 LLIST


9040 CLOSE #3


9050 RETURN





That gets tedious after a while, so a better solution is needed.





What is required is a set of utilities that can be loaded


and accessed easily, which enhance the operating system


provided by Sinclair and which can be customised by the user


to suit their individual needs.





The first requirement is easily met, since Sinclair provided


the facility to save one auto-loading BASIC program on each


Microdrive cartridge. That is done by saving the program


with the name "run"; the file can then be loaded and run


with one keystroke - simply press the RUN key - at power-on


or after a complete reset - typing NEW or RANDOMIZE USR 0.


The demonstration cartridge provided with the Microdrive by


Sinclair utilises this technique.





My own system grew as I either thought of new things to add,


or became irritated with the long-winded syntax, or both.


Loading, erasing, merging and producing a cartridge


catalogue are the commands used most often and also the ones


which require you to hop on and off the shift keys in a very


unfriendly manner. So they were my first choice for a simple


utilities system.





A utility to load a program of any sort saves typing:





LOAD *"m";1;"... your filename





each time - ten keywords/characters, seven of which require


the shift key. The utility is in lines 8000-8099 of Listing


1. A similar utility for erasing a file saves nine


keywords/characters, and is given in lines 8700-8799. I will


leave file merging until later as that has other implications.





My first catalogue facility simply did a plain CAT 1, which


can only display 22 filenames before the SCROLL? prompt


appears and consequently a cartridge with many files cannot


be catalogued on one screen. Printing a catalogue list


requires a stream to be opened, as for the LLIST example


given above. Lines 8200-8299 of Listing 1 give a routine


which tries to present you with the best of both


alternatives; either a simple printed list or a routine


called "neat catalogue" from the book Master Your ZX


Microdrive by Andrew Pennell. The "neat catalogue" routine


formats the output on the screen into two filenames per line


and adds titles to make it less cryptic. However, the


machine-code element of the latter, stored in a microdrive


cartridge file called "stream14z$", is missing, as Pennell


retains the copyright of this. So you have two choices:


either replace lines 8220-8290 by:





8220 CAT 1: PAUSE 0: GOTO origin





or buy the book.





You will have noticed several things about the listing which


need explanation. A variable called "origin" has been used


at the end of all the main menu option segments to redirect


control to the main menu. That has been done for two reasons


of which the most important is flexibility. The variable


"origin" can be reset before calling the segment by a simple


LET statement. The second reason is because I have used


GOTOs rather than GOSUBs as some routines cannot be RETURNed


gracefully. Note that the CLEAR statement at line 7005 will


cause "origin" to lose its value, so always set it to 7010


rather than 7000.





Another point of style concerns the routine at lines


9941-9949 which is used for choosing input options. The


routine uses two parameters, "highest" and "lowest", which


must be defined before calling the routine to ensure that


only the required range of numeric keys can be used. All


other keys, except BREAK, are inoperative, which should


prevent unnecessary crashes and other odd things from


happening. The third point is that a variable called "baud"


is set in line 7120. That can be altered if your printer


will accept a higher baud-rate than mine.





Returning to the main-menu options, an early challenge after


I bought the Interface 1 was to link it to my printer via


the RS232 port. As my printer is a Tandy Lineprinter VII,


that was not a simple task. I ended up experimenting with


ways of producing a pixel by pixel screen dump. Lines


8300-8399 give a routine which should work with the Seikosha


GP8O/GP100, the Epson MX8O/FX8O/RX8O and the ZX Printer.





The Epson routine has been tested on an Epson FX8O. The


Seikosha routine has not been tested, but as Seikosha makes


the Tandy printer and it seems similar in operation, it


should work. The ZX Printer version simply uses COPY.





I make no apologies for the appallingly slow speed of the


routines, but leave it as an exercise for the reader to


produce a quicker version, probably by resorting to machine


code.





After a menu asking which printer you have, you will be


asked which screen-file you wish to print. Since LINE INPUT


has been used, simply pressing the RETURN key will produce a


printed version of whatever is on the screen at the time.


Otherwise you must give the name of a SCREEN$ type file


stored on the cartridge and you will see from the listing


that I use a convention here which I have incorporated into


the program.





As the catalogue of a cartridge does not distinguish between


the various types of file - BASIC, CODE, DATA - I restrict


screen file-names to seven letters and add SCREEN$ to the


end of them. SCREEN$ is a token and therefore the suffix is


only three characters long. I recommend that you do


something similar as that has the additional advantage of


performing some validation of the input filename.





The remaining utilities are based on concepts borrowed from


Basicode and in a very modest way the idea of programming


support environments. The latter concept involves the


surrounding of your developing program code with tried and


trusted supporting utilities which can then be used either


as sub-routines for the program or called directly by the


programmer. Basicode is a system which enables software


written in a subset of common Basics to be broadcast by


radio by dedicating certain line numbers to tasks such as


clearing the screen, which are handled in different ways by


different systems. The Basicode will have lines like GOSUB


10; line 10 must then have the machine specific code - CLS


on the Spectrum.





What do these utilities offer? First, the ability to MERGE a


Basic program with the auto-run utilities software - see


lines 8100-8199. Once MERGEd, the program can be run with


the support of the utilities, provided care is taken not to


use line numbers greater than 7000, where the utilities are.


Then, if a screen dump is required, that can be done by


calling the utility in lines 8300-8399; return is achieved


by setting the value of the variable "origin" to the


following line number in your code.





For example:





440 ... your program code ...


450 LET origin=460: LET choice=2: GOTO 8340: REM screen dump


460 ... your program code continues ...





Note that the variable "choice", indicating the second


printer option from the menu given in lines 9921-9929 - that


is, the Epson - must be set first and the alternative entry


point at line 8340 used to prevent your desired screen being


replaced by a menu.





Listing to the printer is also available - see lines


8400-8499 - although I know of only a crude way to stop that


before the utilities section is printed - press the SHIFT


and BREAK keys. Do not worry about restarting gracefully,


because all the routines close the appropriate stream before


opening it, thus preventing a "stream already open" error.


Note that the routine opens stream 4 to channel "t"; all


other printer routines use stream 3 so that LPRINT can be


used instead of PRINT #3;.





Finally, a simple but invaluable machine code utility was


published in the November 83 issue of Sinclair User to block


delete BASIC program lines. I have modified that slightly


(lines 8600-8699) but I acknowledge David Maxwell as


original author. The inclusion of that makes up for a


glaring omission in the Spectrum interpreter/editor and of


course enables you to delete the utilities from around your


BASIC program if you do not need them. The routine asks you


to input the start and end line numbers and then deletes


those two lines and all lines between. An error will result


if you use the routine to delete itself, but it does not


crash the system so other program code is preserved.





I encourage you to extend the principle to your own


individual uses; some possible improvements have already


been indicated. Others that I have thought about for the


future are: 1 - use LIST to a stream, where the stream has


been opened to the microdrive channel; the resulting file is


then in data format and can be searched for keywords or


variable names - when you are debugging, for example; 2 -


set up a screen menu of commonly used programs on the


cartridge, so that programs can be run by two key presses,


one to auto-load the utilities and one to select the


program; 3 - add a line renumbering facility; and 4 - use


MOVE to produce printed listings of any BASIC program stored


on a microdrive cartridge.