Ticker Tape Messages

Eric Martell and Chris Murdock

The large text modes, [GR. 1, GR.2] are very convenient. With text like this available, the Atari can become a useful and eye-catching message presentation device. The following program makes use of some simple string manipulations, to move text across the screen in a manner reminiscent of ticker tape or a marquee sign. The actual text movement is done by line 50 in the following manner:

The first 19 characters of the message string [A$] are printed at position 1.5 [the vertical center of the screen]. A temporary string [C$] is set equal to the second through the 20th characters in A$. Then A$ is added [concatenated] to C$. Since C$ and A$ are dimensioned to be the same length, this has the effect of attaching the first character in A$ to the end of C$. A$ is then set equal to C$ and printed once again.

The variable K is set up to check for any key being pressed. This action will terminate the program in line 55. A delay loop is inserted in line 55 to increase readability, since the string manipulation is so fast that the letters become blurred unless slowed down.

The rest of the program contains enough remarks to be self-explanatory.

Listing: Display card symbols in graphics 1 and 2

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