Tandy gram; third-party DOSes make Color Computer programming easier. (evaluation) Jake Commander.

The following was sent to me from Sepctrum Projects in San Jose, CA. In true cloak-and-dagger style, there was no accompanying letter, so I'm assuming the sender is using me as a forum. It concerns a new version of the Color Computer and is reprinted exactly as I received it.

"Speaking of newer and newer versions of CoCo II: The very latest is 26-3136A and it has a totally revised board. Once again, Tandy has pulled the rug out from under third-party suppliers. For instance, non-standard Texas Instruments RAM chips are installed. The 16K computer uses TMS4416 chips which are 18-pin 4x16's so only two sockets are required, not the eight sockets that we are accustomed to. Because these chips require a 256 (versus a 128) cycle refresh, a new SAM chip is required--a 74LS785. (The previous one was a 74LS783.)

"The VDG (video display generator) is the same, but a new one with true lower case will be in the 26-3136B version of CoCo II and CoCo III. A new 28-pin ROM (the told version was 24-pin) is used for Color Basic and Extended Color Basic (yes, one chip for both Basics). Basic is now version 1.3 and is soldered in rather than socketed. If a non-extended 16K computer is made with this board, it will be supplied with a 24-pin Basic chip plugged into a 28-pin socket, or maybe soldered into the location. There are 12-pin connectors near the RAM chips and some jumpers marked '128K RAM' so we can expect some kind of a satellite board next year for that upgrade. (The 64K upgrade may be via satellite board as well.) The 74LS244 buffer has been changed to a 74LS623.

"Finally, the disk controller has been completely redesigned. The part number (AX7980) is the same but there are fewer chips used. They are: a new Western Digital 1773, which is a 28-pin floppy disk controller chip, and seven others (74LS74, 74LS14, 74LS139, 74LS02, 74LS273, and two 74LS16s). The new controller clock speed is 16 MHz rather than 10 MHz."

Thanks to Spectrum Projects for that information. It shows how difficult it can be for independent third-party suppliers to keep abreast of Tandy's intentions at the hardware level. The Color Computer continues to be rejuvenated--maybe Tandy hopes that it will become their Apple II

Motorola has had a chip set available for some time which allows a high-resolution display with 64 different colors. for a while rumors abounded that Tandy (whose Color Computer already contains a Motorola chip set) would release a 64-color computer. They denied it all as usual. But you can tell. There's a prototype or two somewhere. . . .

Now at last for the reviews I promised last month. I've taken a look at two disk operating systems for the Color Computer. The first is ADOS from SpectroSystems. The second is Spectrum DOS 1.0 from Spectrum Projects. The products share many similarities, but I'll go over each one separately rather than comparing side by side. ADOS

First, ADOS which describes itself as "an enhanced, ROM-able Disk Basic for the Radio Shack Color Computer, 64K required for RAM use." The statement about RAM use is interesting in itself. As the regular Tandy DOS is contained within the plug-in ROM cartridge at the side of the computer, there are two ways in which a new DOS can take over. The first involves switching to a memory map whereby 64K of RAM is addressed. This 64K contains the new DOS. The other way is to extract the ROM from the disk controller ROM pack and insert a different ROM containing the required DOS. So ADOS can be implemented either from RAM in 64K mode or from ROM if you have the ability get an EPROM burned in. The ADOS manual gives addresses of two services that can do the EPROM programming for a mere $20 including the chip.

Brief descriptions of ADOS features are listed in Table 1.

Also included on the latest version of ADOS is an ERROR command which provides error trapping within Basic. The manual for ADOS consists of 11 pages of clearly written text which I though was OK. This isn't glossy magazine stuff. It is a concise description of the DOS commands and how to use them written for someone who already understands Tandy's DOS.

I liked the repeat-command feature. I wish all operating systems (disk or otherwise) had this facility. How often have you typed in a long command line only to have the computer throw it back at you for a single typo? ADOS lets you edit the last command line using the Basic line editor. Simply entering a slash brings up the entire last line input with the edit mode invoked. You simply correct any typos and press Enter. The command is then handed back to the computer as if you had retyped it. This is a nice feature.

I found the lowercase entry of commands to be another nice feature which worked well with my lowercase mode. I use Dennis Kitsz's lowerkit and constantly find myself in lowercase simply because it is less ugly than the Tandy inverse uppercase. Hence, the computer keeps complaining about syntax errors just because of the case I happen to be in while typing. ADOS brings some sanity back to that scenario by happily working in either case.

For those of you who are still limping along in uppercase only, a high-resolution text screen utility is provided. This lets you choose 42.51 or 64 characters per line. I wish 32 characters per line had been included so you could have a simulated low-resolution lowercase driver. However, this is only a barebones utility which doesn't react visibly to a CLS command or the Clear key.

The PRT ON/OFF command, which lets you concurrently send output to both screen and printer, is another goody. This is always useful. You can capture the printed output of an entire program without having to change all the PRINT statements to PRINT #-2 statements. The PRT ON option is apparently used when using the DIRP and CATP commands. DIRP sends the output of the DIR command to the printer and CATP sends the output of a CAT command to the printer. DIR is the same as the Tandy DIR command except that the number of free granules is printed at the end. CAT gives a two-column directory, letting you get more information on a single line. Using CATP gives a printed directory suitable for attaching to a disk envelope.

The reason I say that DIRP and CATP both invoke the PRT ON command is that if you hit Break during the output of the directory, you must type PRT OFF to disable the printed output. I don't like that. I think it is the responsibility of the operating system to deal with such situations.

A similar situation arises when the SCAN command is used. This lets you list the contents of an ASCII file or gives you the addresses involved with a machine code file. However, interrupting a file scan with the Break key requires a CLOSE command to be issued to avoid a subsequent AD error. This is only a minor problem, but it seems such a pity to allow the hard work involved in writing a DOS to be compromised by simple Break-key trapping. (Maybe previous Tandy Gram columns will help!)

The last thing I'll have room to discuss is the monitor command. Invoked with the MON command, this lets you examine and change memory in a manner similar to the ZBUG monitor that comes with the EDTASM+ assembler from Radio Shack. Many operating systems are equipped with facilities for debugging and this simple version makes up for the omission in Tandy's DOS. Spectrum DOS 1.0

Next on the agenda is Spectrum DOS 1.0. This has many similarities to ADOS in that Radio Shack compatibility is maintained, some of the commands provide the same features (even using the same command names), and it, too, can be burned into an EPROM. Customizing utilities are also provided. The run-down of Spectrum DOS 1.0 commands is shown in Table 2.

First, a word about documentation. The manual is not a strong point, I'm afraid. I would never have dared turn anything like this over to my English teacher. Phrases like "bingo your in Spectrum DOS," "without the lose of your program," and "a inverse F" tend to lessen my confidence in any product no matter how high its apparently quality. Also, at a mere six pages, this DOS is ill served by its manual. A little more discussion of some of the commands would serve both to illustrate and encourage their use.

One thing I do like about this DOS is that it automatically searches all drives when looking for a program. I shouldn't even have to comment on a feature such as this which should be standard in any DOS whether it be for a Cray, a Color Computer, or a programmable calculator. Tandy was not thinking when they left if out. Spectrum DOS also lets you use any number of tracks on your drive so you can hook up an 80-track drive if you wish.

Along with other enhancements to life in the direct mode, DOS 1.0 lets you redefine both the cursor character and the READY prompt. A keyboard repeat feature is part of the package; to repeat a key, simply hold it down and the character shifts to second gear.

The high-resolution text screen is well integrated into the DOS. It doesn't feel like a separate software driver. The Clear key and the CLS command both work properly, and it is simple to revert back to normal low-resolution graphics with the NORMAL command. The Basic PRINT @ command is extended to work in any print density. However, no check is made for a PRINT @ where the character is off the screen, and I did manage to crash the DOS when I tried a PRINT CHR$(129) followed by EXIT to lo-res then LIST.

The LMOVE and LCOPY commands add a nice feature to Basic. Both commands allow you to copy Basic lines from one part of a program and place them in another. LMOVE deletes the old lines, whereas LCOPY leaves them intact. Another nice command is OLD. Have you ever had that flash of panic when you typed in NEW and realized you hadn't saved the program first? Nasty isn't it? Salvation is at hand with the OLD command. As long as you don't add any line numbers after your NEW command, OLD will restore the program you absent-mindedly erased.

Finally, I'll mention the HELP command. This is another command that should be available in any "real" DOS. Typing HELP brings to the screen a display of all the new commands along with the required syntax for their use. Summary

Both of these disk operating systems have much more to offer than I have room to cover here. As for which one is better, I find it difficult to decide. Spectrum DOS 1.0 may have a slight edge, but I'm not comfortable with the thought that I could crash it so easily. ADOS stayed intact during my wild forays into its commands. A scan through the features of each DOS versus your own particular requirements will be your best guide.

The manual of Spectrum DOS 1.0 ends with a quaint quote which I can't resist passing on as an epilogue:

"Every precaution has been taken to assure that this program is error free, but there is no program in existence that it totally bug free. So if one is encountered please let us know." So folks, if you find a bug-free program. . . .

Products: ADOS (computer program)
Spectrum Dos 1.0 (computer program)