An enhanced keyboard and screen mode for Color Computers; Tandy gram. Jake Commander.
First I'd like to say a big "thanks" to those of you who have taken the time to write to me with your ideas regarding this column. Forgive me for not being able to personally reply to all of you; there are simply too many letters to answer. Nevertheless, any that are of general interest, I'll address in this column. Your suggestions range from programs to reviews to more specific interests. In other words everyone would like to see everything. Ah well, nobody said it would be easy, and I'm happy to note that TRS-80 users are as enthusiastic as ever about their machines.
This month I'm devoting the column to a 6809 machine-code program for the Color Computer which I've entitled Chroma-Key. It is a utility that allows you to use the keyboard and screen in an enhanced mode something like (dare I say it?) the Commodore 64. Model I/III/4 users needn't feel left out though; a similar program for Z-80 people will follow in this column next month if space permits. This program is on the large side so it is split in two--half this month and half next. (Remember, too, the CompuServe subscribers can download the program from Creative Computing Online (PCS-22).) When you have the whole thing typed in and assembled, the following functions are available:
* Repeating keys with lowercase on Shift.
* Twenty-seven predefined keys. Shifted A to Z and Shift/right-arrow are all defined as various Basic commands.
* Redefinition of keys so that a single keystroke can enter a whole word or sequence of words. The whole definition table can be saved to or loaded from tape.
* A screen editor with allows entry and editing of characters on the video display. A special graphics sub-feature allows easy entry of low resolution graphic characters.
When the output feature is invoked, the keyboard definitions are saved on tape as a file named KEYDEF. I'm afraid I never did find time to add the disk save feature, so if anybody wants to volunteer, I'll be happy to include it in a future column. The list of predefined keys will appear next month after the end of the listing.
For those of you who have never tried your hand with EDTASM+ on the Color Computer, now is your chance. I should point out that this listing appears as output from the assembler during the assembly process. The first three columns printed by the assembler simply show addresses in memory followed by the bytes that are to be loaded there. As data-entry operator, you need to type in only the information that appears after each line number. If you are crazy enough, you can use the first three columns to key in the machine code in hexadecimal. (Does anybody still do that these days?) However, the more sane among you will fire up to EDTASM +- or whichever is your favorite editor-assembler--and start off by entering I10.
The line numbers in the listing are stepped in tens from 10 to 4820, so you have only 482 lines to enter without making a mistake. Dead easy. Now you see why this is in two parts.
Note that the version listed is for a 32K machine. To get the program working on a 16K machine, you will have to alter line 130 from 7C00 to 3C00; it's that simple. The comments in the listing serve to illustrate how the program works. I don't intend to go into further detail on that score, unless there is a demand for it, as this project already seems to be occupying the greater part of two columns.
Next month you'll have the second half of the listing along with the instructions to enable you to use the utility.