PREFACE
Since you've picked this book up and started browsing through it, you probably own or have access to an ATARI computer and are interested in progressing beyond BASIC. As you already know, the ATARI computers are among the most impressive of all home computers, but many of their special features are not available from BASIC.
This book is designed to teach assembly language programming to anyone who understands ATARI BASIC. Yes, anyone! You've probably read other books and articles which create a mystical aura around assembly language, or else use the phrase machine language as if it were the secret code to unlock the door to the Thief of Bagdad's treasure troves. Of course, only the privileged get to look at this secret treasure.
Bunk! Anyone who has programmed in BASIC, or any other language for that matter, can learn to program in assembly language, given the desire and the correct instruction in the language. This book provides the tools you need. Each programming language – BASIC or PILOT or FORTH or, yes, even assembly language – has its own words which stand for certain operations. One example is PRINT in BASIC, which directs information to your TV screen. The combination of these words, and the way they must be strung together to make the computer do what you want it to do, is called the syntax of the language.
In this book, you will learn the syntax of assembly language, and you will also learn, by frequent examples, how to use assembly language to make your ATARI perform tasks which are either impossible from BASIC or 200 times slower in BASIC. The examples are fully documented both by frequent remarks and by a thorough discussion of the purpose, programming techniques, and theory, where appropriate, of each program. This discussion allows you to progress beyond the examples and to write your own subroutines or even whole assembly language programs for the ATARI. Furthermore, the routines in this book follow the "rules" established by ATARI for assembly language programmers, so they will work with any ATARI computer, from the earliest 400, to the most advanced 1450XLD, and everything in between.
Examples are given both in assembly language and, wherever possible, also in BASIC programs which incorporate these assembly language routines to perform tasks from BASIC. These routines can be used immediately in your own programs. In fact, you can use the enclosed order form to obtain on disk all assembly language and BASIC programs in this book. The disk is ready to run or modify for your own uses. Included on disk and here are such techniques as reading the joysticks, moving players and missiles, input or output to all possible devices such as printers, disk drives, cassette recorders, the screen and more, vertical blank interrupt routines, display list interrupts, fine horizontal and vertical scrolling, sound, graphics – in short, everything you've always heard the ATARI computers were capable of but had no idea how to program.
One entire chapter of the book is devoted to the use of assemblers and how to use this book with any of the many fine assemblers available for the ATARI computers. You'll need an assembler, just like you need BASIC to program in BASIC, and this book will interact with any of them.
If you've reached the point where BASIC is no longer enough, and you'd like to progress to a language which gives you absolute control over all functions of your remarkable computer, then begin with Chapter 1, and you'll see how easy it is. Who knows, maybe you'll be the one to write the sequel to STAR RAIDERS!
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