Commodore's port. (column) John J. Anderson.
First off, keep those cards, letters, and especially manuscripts rolling in. I have been quite favorably impressed by the overall quality of the Commodore submissions we have been getting. At this rate, the Creative Commodore programming books will be among the strongest available for any micro around. Keep up the good work, folks.
Let's make a brief diversion to the mailbag. Mike Steed, of Provo, UT, wrote in with the following fix:
"In the July 1983 issue on page 176, Eric Luce and James Wheeler presented an excellent program using redefined characters, they moved the start of Basic to $1801 (6145 decimal). This is very handy, except for one thing. The RUN command without a following line number, and NEW, will return an error message.
"This can be prevented quite easily. For some strange reason, Vic-20 Basic requires a zero byte at the start of Basic minus one.
"So, to remove the error message after those strange POKEs, and POKE 6144,0 to line 30 in listing 1, preferably before the NEW. Also, add the same command to both of the immediate-mode sets of POKEs."
Okay, Mike, we will do so. Still Seeking Resolution
We have also received many responses to our piece on Commodore 64 video resolution. A few monitor owners wrote in with the same fix as Mark Kuene, of Eau Claire, WI. Mark stated the following:
"I recently bought a Commodore 1701 color monitor for my Commodore 64. Unfortunately, when I used the two-cable jack supplied with the monitor, light vertical lines appeared on the picture. This problem is described in the August 1983 Commodore's Port.
"The problem can be remedied by using a three-jack cable connected to the optional three-jack input on the back of the 1701 monitor. The same five-pin DIN jack can be used to plug into the 64, but the cable will have a separate luminence line added.
"Connect the luminence output of the C-64 (pin 1) to the jack labeled LUMA, the video output (pin 4) to the jack labeled CHROMA, and the audio output (pin 3) to the audio input jack. A pin-out diagram is shown on page 142 of the Commodore 64 User's Guide.
"Through the addition of the luminence output, a much sharper picture is obtained, the colors are purer, and the troublesome vertical line are eliminated completely."
Thanks, Mark. Speaking of the Commodore 1701 monitor, I recently saw a retail price of $240 for the unit. This has got to be one of the best prices around for a quality NTSC monitor. And if you have C-64, it is the only logical choice. What a difference it makes in video quality.
Nonetheless, we have gotten many letters from disappointed owners of C-64s, some with color monitors, suffering from a problem Compute magazine recently christened "sparkle." This glitch results in a distracting glitter effect across the screen. One of the 64s we have here at the lab has a really bad case of the sparkles, for which Computer faults a ROM problem. It makes certain programs very hard to watch, and certainly spoils many graphic effects. Even text screens are affected. At press time, Commodore had yet to officially acknowledge the problem or state when a fix would be available.
Rest assured we will keep a close eye on the Commodore video story and update it again soon. As soon as a sparkle fix is available we shall report on it. The Key to the Commodore Keyboard
When you take your new Vic-20 or Commodore-64 computer out of the box, the keyboard of the machine immediately offers a challenge. Staring at it, you can almost hear it say "I dare you to make me do something."
Of course you can make it do things without learning much about the keyboard. You might choose to learn only the commands that load prepackaged software into the machine and get your C-64 or Vic-20 to do some neat things. But if you want to do more, you will have to learn more about the Commodore keyboard layout.
The keyboards of these machines are easy to learn, but have their little tricks. Sometimes something works one way, then later in another, leaving you perplexed as to why you can or cannot get certain keypresses to work.
Another aspect of the keyboard that can be confusing is the concept of special graphics characters. They have their own special meanings and are sometimes hard to find on the keyboard. This kind of problem often surfaces when you are typing in a listing from a printed source. You know what the character is, but you don't know how to get it to appear.
Boston Electronic Systems Training has released a keyboard tutorial, called Best Keyboard Coach, for the C-64. It uses an audio cassette, along with animated color graphics programs, to provide painless familiarization with the Commodore keyboard. A second program offers interactive drill and practice.
At $20, I can't think of any beginning C-64 owner who would want to do without it. As I have said, getting past the keyboard is the first real hurdle. For more information, contact Boston Electronic Systems Training, Inc., 24 Munroe St., Newtonville, MA 02160. (617) 969-2378.
About the most common questions we get about Commodore computers concern keyboard problems. Let's hold a short tutorial on the subject right now. Even if all that follows seems utterly simple to you, try reading it through. It might help clarify things in the long run.
When you turn on your Commodore machine, it defaults to the caps mode. In this configuration all letters are printed out as capital letters. Shifted characters print out as special graphics shapes, as depicted on the front righthand side of each key. Make sure you are always in this mode when programming. Otherwise you can end up making things tough on yourself or others later.
The other mode you can choose is lowercase, which is turned on and off by pressing the SHIFT and Commodore logo keys simultaneously. The screen characters will then resemble those on an ordinary typewriter, with capital letters appearing when SHIFT if pressed.
To get the graphics characters on the lefthand side of each key front, press the Commodore logo key along with the key that depicts the shape you want. That's all there is to it.
But not every graphics character is depicted on the keyboard itself. There are some mysterious but especially powerful ones you should get to know, and you will, quite soon.
Why problems occur if you program in the lowercase mode will become obvious if you look at mixed caps and lowercase text from the caps mode. All the capital letters will have reverted to graphics characters. I once wasted a great deal of time trying to load a file name with caps that had been entered from the lowercase mode. File names with graphics characters in them are rather inconvenient to type.
This problem may also drive you crazy looking for graphics characters when typing in a program. Stay in the caps mode, unless there is a very good reason to go to lowercase. A good rule of thumb is to use the lowercase mode only when running, as opposed to editing a program. If you are editing lowercase text, shift back regularly.
You may also have noticed that something funny happens after you type a quotation mark. When the Commodore editor sees a quote, it puts the computer into what in other machines is called an "escape" mode. That means that rather than executing a keyboard command, it puts the message to execute that command into a print statement within the very program you are typing. If it sees a second quote, it returns to normal.
Outside a quote, CTRL-BLK will turn the cursor, and all subsequent characters, black. Inside a quote, a special character will be inserted, which tells the machine upon execution of that line to turn the cursor black.
This is where all the mysterious special characters come into play when typing program listings. It takes more than just a little while to get to know these characters when you see them, let alone what they mean and how to obtain them. But my suggestion is to work on it. There are only 22 really important ones. At the least, learn to recognize them.
Figure 1 is a listing of the prevalent ones, and how to get them to happen on the keyboard. Consider cutting out Figure 1, gluing it to some card stock, and keeping it near your computer.
You will also notice that the last column in Figure 1 gives a special numerical code for each character. In some program listings, these CHR$ numbers are used rather than special graphics characters. For example, instead of printing an inverse heart to clear the screen and home the cursor, you might say PRINT CHR$ (147) accomplish the same task.
Although this technique avoids the use of graphics characters, it makes program listings harder to understand--unless you know which codes are which. I think it is easier to associate a graphics character with a special command than a number. For that reason I avoid this approach in my own programs. However Figure 1 is a good reference to consult when you see CHR$ commands in other programs.
So you see, he secrets of the Commodore keyboard are not difficult at all once you learn what they do and why. My advice is to start experimenting.
Next month, among other things, we shall examine wedge programs for the Vic-20 and the 64, and see how they can make life much easier for the Commodore computer owner. See you then!