Tandy's Little Wonder (1993)(Farna Systems).pdf - TRS-80 Color ...

As I began to develop ADOS, I was faced with the problemof what features to include. I knew I had a limit of 2K ofspace to work in. Two K does not sound like very much—amodest-sized BASIC program takes up more space thanthis—but I rapidly discovered that many BASIC enhancementscould be accomplished using surprisingly few bytes.My addition of RUNM to the command set required only 18bytes; allowing COPY to took37 bytes. This economy was made possible by the fact thatmany pre-existing ROM routines could be called to accomplishparts of the task, and I made maximum use of suchroutines to squeeze as much as possible into my 2K.During the early phases of development, I did not feelsqueezed for space at all; after putting in various enhancementsto BASIC that had occurred to me early on, I still hadquite a bit of space left, and began to wonder if I would be ableto fill it. I began casting around for suggestions on Compu-Serve and in a Miami CoCo users’ group I was then attending.Pretty soon, I had more than enough to fill 2K. I found myselfporing over already-written routines, modifying the code tosave a few bytes here and there in order to squeeze in this orthat additional feature. The original Microsoft ROM codeprovided me with an excellent model to imitate; it is extremelyeconomically written with regard to accomplishingtasks using a minimal number of bytes. The code for theCoCo 3’s Super Extended BASIC, written much later atMicroware, is much less efficient.In April, 1984, when I had a preliminary version of ADOSready, I sent a copy to Dennis Kitsz, hoping that the tie-inbetween his Lowerkit and ADOS’ support of lowercasecommands might lead to some sort of commercial collaboration.I heard nothing for months and then got a call fromhim. This was something of a thrill for me, since I had in myvery early CoCo days been an eager reader of his CoCoarticles in 80 Micro. We wound up sharing a booth at anumber of RainbowFests, beginning with the September,1984 Princeton one at which ADOS officially debuted.When the CoCo 3 appeared, I wanted to have a version ofADOS that supported its features, and so began work onADOS-3. There was very little room to add any featuresbeyond those present in ADOS, since the ADOS enhancementsentirely filled my available 2K. But I managed to makea little room by taking advantage of the fact that BASIC runsout of RAM on the CoCo 3, which allowed certain routinesto be rewritten. Also, ADOS’ ON ERROR GOTO and RAMcommands were no longer needed, so that gave me someextra bytes to work with. I was particularly interested thatBASIC should support the CoCo 3’s double-speed mode,and modified disk and printer routines while adding FASTand SLOW commands. I also allowed ADOS-3 to be configuredto boot up in 80-column mode. ADOS-3 was introducedin January, 1987 at the Color Expo in Anaheim,California.One thing that disappointed me about the CoCo 3 was that itsinternal ROM was soldered in. Had it been socketed, I wouldhave strongly considered having ADOS-3 reside there, sincethe internal ROM contains plenty of free space (6K of whichis taken up by the infamous "Three Stooges" graphic). Toremove that ROM and install a socket would require somedelicate soldering, which struck me as a highly undesirablerequirement for a commercial product. Still, after releasingADOS-3, I was itching to include quite a number of additionalenhancements—I had a backlog of ideas and suggestionsby this time—and so began to consider a secondpossibility for where to place the required code.From the outset of ADOS, I had been aware that a diskcontroller could accommodate an EPROM with 16K ofspace rather than 8K. The problem was that this could onlybe done with controllers having a 28-pin ROM socket due tothe fact that the only suitable EPROM was the 27128, whichhad 28 pins. All Tandy controllers had 24-pin sockets. Asolution was to offer a 24-to-28-pin adapter for the Tandycontrollers, and I had a source of these, a fellow by the nameof Jim Smith that I had met at a meeting of the Miami CoCousers’ group, who made them by hand. These were originallyoffered to ADOS users simply as a convenience, since 28-pin EPROMs were cheaper and easier to obtain than 24-pinones, and since some CoCo EPROM burners were incapableof handling the 24-pin type. Since requiring an adapter madethe product less attractive, I had decided to confine ADOSand ADOS-3 to an 8K EPROM, even though that limited meto 2K worth of enhancements. With the passage of time,though, two developments occurred that rendered an adapterunnecessary for many CoCo users to use a 28-pin EPROM.First, third-party controllers became considerably morepopular, especially with the more experienceed CoCo usersthat ADOS primarily appeals to. These third-party controllersall had 28-pin ROM sockets. Second, Tandy came outwith the FD-502 controller, which contains a 28-pin ROMsocket, although a minor modification is required to use a27128 EPROM. Therefore, I began to develop ExtendedADOS-3 to fit together with ADOS-3 in a 16K EPROM.After having had to squeeze everything into 2K, watchingevery last byte, having another 8K to work in seemed like thelap of luxury, sort of like moving from a closet to a mansion.When I began, I never felt I would come anywhere near tousing the whole extra 8K, even though I had quite a few thingsI wanted to add. These included a RAMdisk, which MartyGoodman had been begging me to put in for some time; amenu-driven utility for selecting files to execute, kill, load,copy, etc.; fast BACKUP and DSKINI; wild-card copy; filedatingthat supported real-time clocks; block move and copyof BASIC program lines; and various other miscellaneousgoodies. As things turned out, I came a lot closer than Iexpected; less than 1K was left unused, and I had includedpretty much everything on my "wish list". Extended ADOS-3 debuted at the Chicago RainbowFest in April, 1989.page 42Tandy's Little Wonder