¢THE ATARI 8-BIT BOOKSHELF¢¢ADVANCED PROGRAMING TECHNIQUES FOR YOUR ATARI by Linda M. Schreiber¢1983 Tab Books Inc.¢¢Reviewed by Joseph E. Hicswa¢Ol' Hackers A.U.G.¢March 16, 1996¢In the Public Domain¢¢ I got Advanced Programming Techniques for your Atari about 8 years ago and read it several times. From this last particular reading I learned to translate machine code into a BASIC language program. BASIC, especially TURBO BASIC is my preference because of easy-to-read structure. High level languages meant learning something hard, like Latin, Polish, or some other hard language. But I'm happy with ATARI BASIC. The BASIC language programs permit myself and others to list, examine, improve and share with other ATARI users.¢¢ Linda wrote about, and explains programming techniques in easy-to-read understandable format. She reinforces her topics with 64 programs, REM statements and line by line explanation. Familiarity with BASIC language is helpful but not critical as she guides you through the BASIC programs. The book is replete with easy programs for the reader to enter into the computer and see the marvels on screen. With a little ingenuity readers can alter and improvise those programs that fascinate ATARI users.¢¢ Programing makes me feel like a demigod, whereby I get an idea then program it to become reality on the computer screen. What a happy accomplishment!¢¢ Linda's book teaches people to write outstanding programs and make their ideas a reality also. In her introduction Linda explains she wrote for the person who wants to get more special effects, more sounds and more graphics from an ATARI computer. She does this in fourteen chapters.¢¢ Starting with an explanation of the binary system, the reader is guided through all of the following, such as ANTIC (text & graphic displays), animation, how to speed up a program, machine language subroutines, display list interrupts, scrolling, page flipping, sound, keyboard magic, memory locations to do fancy screen displays, workings of a disk drive to make boot disks, voice (audio) programs for Cassette users.¢¢ Linda explains where the character set is located, how to copy from ROM into RAM and alter it for fascinating color displays on screen by simply pressing computerboard keys. (An altered character set was used to program EASTERN FRONT--WWII battles in¢Europe).¢¢ For years I had wanted to learn about the numbers programmers used in their DATA lines. People who knew and understood them had tried explaining, but I couldn't grasp it. Then I discovered something in chapter 7 - DISPLAY LIST INTERRUPTS - using machine language subroutines. It came through loud and clear. The numbers are machine language codes poked into computer memory to speed up the program and make it run smoothly. The codes are tokens (the alphanumeric characters in an ATARI-ATASCII-list. Depending upon instructions, a computer treats a number as a token or number. As tokens, 72 represents UPPER CASE H, 198 is a graphics character and 162 is inverse quote marks. When told there is a machine code token in the memory location, the computer performs that certain function.¢¢ Dec Code Mach Code¢ 72 = PHA ;Push accumulator¢ on the stack.¢ 138 = TXA ;Transfer index X¢ to accumulator.¢ 162,100 = LDX #100 ;Load index X¢ with 100¢¢ Now I don't understand the mnemonics, but it was a revelation non the less. All I have to do is make a list of decimal codes and respective machine language codes. The list would then be used to translate machine language programs into my BASIC language program to poke machine code numbers into computer memory.¢¢ A=USR (address). USR tells the computer it is a machine code routine. The address is where it begins. The book reveals memory locations.¢¢ DATA 72,138,162,100¢ FOR L=n to n+3:READ D:POKE L,D:NEXT L¢ A=USR(n)¢¢ If you are unable to find a copy of this book then check your local library. They also might have other ATARI books available. After reading Linda's book to discover ATARI secrets, why not tell us about it in an article? Happy reading and programming.¢
