Products in Review

The first review is on Scientific Software’s TS100/ZX81 Assembler Debugger (ZXAD) (See the unclassified ads for ordering info) While I have used, both for enjoyment and on engineering jobs, many assemblers, debuggers, and monitors; I have only tried two on my Sinclair. Note my comments in an early issue on the serious shortcomings of the first one I tried. Well, Scientific Software’s version has turned things around. The ad pretty well describes its features, and the inclusion of ‘normal’ pseudo ops makes this assembler well worth the money. A few words about the REL pseudo op, which is not featured in all assemblers. It allows you to assemble and inspect your machine language program in one area of memory and then use REL to move it to another. It takes care of all the address changes, etc. Since ZXAD is resident during program development, you cannot put your object code in a 1 REM …. statement. You can move RAMTOP and put it there originally and then when debugging is complete you can delete ZXAD, use REL, and put your code in a 1 REM. I put mine in the ‘hidden’ memory above 8k in my 64k memory. As for using ZXAD, it was a dream to use and only one problem was encountered. It requires a space after the REM if no label is used. The space you get ‘for free’ when you enter REM does not count, you have to add one more. The debugger is a rather ‘primitive’ one as debuggers go and I am in the market for a better one. It allows you to examine & change memory contents and to set a breakpoint. Unless I screwed things up, to execute the code assembled with ZAD, you enter PRINT USR (start address). Well, knowing my code had bugs but not knowing where, I put in a breakpoint and tried to run it. The program began to chase rabbits and I had to hit reset to regain control. This puts you back to square one! Most monitors I have used sort of artificially run your code and you can usually return to the monitor without reloading everything. As for program storage, I simply saved a copy of ZXAD with my source code in REMs (starting at the end of ZXAD). As for documentation, it consists of 21 half pages, is well done and thoroughly explains ZXAD. Missing is a nice simple example for the novices that are just moving into ‘serious’ machine language programming. However, if you will stay tuned to Qzx I will come up with some and will be working with my S A S sort routines converting them to machine code. In summary, I highly recommend this one and am looking forward to using it a lot more.

Here’s a brief ‘review’ of the Mule Electronics (444 Lincoln Blvd., Venice, Calif.90291) keytop symbols, sent to us from Bob (WA6DLI). He was extremely well pleased with them as was George (N3CHT) who sent a nice letter along with several articles. The colored keytop symbols, with pressure adhesive are a real bargain at $9.95. They come with clear concise instructions and even have two sample keytops for you to experiment with. If you are too feeble to put the samples on, or if they won’t fit your keytops, you can return the ‘kit’ for a refund. By the way, these keytop symbols are for the surplus add-on keyboards, such as the $19.95 one I described earlier. The ‘kit’ also contains useful info on choosing and wiring an add-on keyboard. In summary, it looks like Mule Electronics has a winner for the add-on keyboard buffs. Its a shame they weren’t around when I cut the black & white ones out of my Sinclair manual and spent hours taping them on.