HELP!

AUTOBOOT FOR CASSETTES

In ANTIC, Oct. 83, page 78, the additional information will clarify properly procedure. Just prior to "Step 6" add this:

You should now remove the program: tape and insert the tape on which AUTOCAS has written its short program (the header). Then CSAVE your BASIC program to this tape. If you have done it right, it should be immediately behind the header.

MAKE A FACE

In the article "Make A Face" (ANTIC, October 1983) there is an error in Figure 1 on page 54. The numbering on the second row of pins on the leftmost DB9 jack is reversed: the order should be 6, 7, 8, 9. The signal ground should be connected to pin 8, which is the third pin from the left in the second row. If pin 7 is used, damage to your printer and/or computer may result. We deeply regret any difficulty this may have caused.

SPACE CASE

In "Binary Autoload" (ANTIC, p. 86, September 1983), the spacing in line 3030 of the listing is misleading. For the program to work correctly, there should be twelve spaces after D: and before the final quote sign in line 3030.

+45 = -45?

"3-D Fuji"(ANTIC, August 1983) is the most interesting article I have ever read. However, it tends to be a bit confusing. The example in Fig. 1 shows the Z axis at -45 degrees (rather than at +45 degrees as stated in the article). In addition, the X projection (TX) would actually use the cosine, and the Y projection (TY) the sine; this keeps the signs straight.

Joseph A. Gillis, Jr.
Annapolis, MD

You're right. Plotting 3-D graphics on a two-dimensional screen can be confusing! Unfortunately, many computers - including the Atari - make the confusion worse by setting up screen co- ordinates in a different way than standard mathamatical graphs. The Atari makes Y values larger as you move from the the top of the screen towards the bottom; standard graphs make Y larger going from the bottom to the top. Atari also uses due "south" on the screen as 0 degrees for plotting trig functions; conventional usage has 0 degrees at due "east." Thus, -45 degrees in a conventional system is equivalent to +45 degrees on the Atari. Since the equations in the article were part of a program written in Atari BASIC, we used Atari's conventions. --ANTIC ED