DATAMAX UV-1 Zgrass LESSONS
              (C) Copyright 1981 Real Time Design, Inc.
                          October 27, 1981


LESSON 0  READ ME FIRST


     Zgrass is a graphics programming language. It is probably closer to BASIC 
than any other language, yet it is much more flexible and general than BASIC. 
The presumption in these lessons is that you already know how to program BASIC 
(at least BALLY BASIC) and are familiar with loops, IF's, GOTO's, variables, 
and so on, and are ready to learn what makes Zgrass tick. The essential 
differences between Zgrass and BASIC are:

1. Zgrass allows any number of programs and subroutines, each named, and they 
can run in series or parallel. BASIC has one unnamed program and a lot of 
GOSUB's.

2. Zgrass has an interactive full-screen editor. BASIC edits with line numbers.

3. Zgrass has good ways of passing arguments to subroutines; BASIC has none.

4. Zgrass can construct programs and run them with string manipulation 
features; BASIC cannot.

5. Zgrass has excellent debugging aids: single step, run-time listing, and 
error trapping; BASIC doesn't.

6. Zgrass has fast, advanced graphics commands; most BASICs use peek and poke.

7. BASIC has FOR/NEXT. Zgrass does without.

     In order to learn Zgrass, you will have to explore it. Fortunately, this 
is not hard and is very rewarding. These lessons are to help you start 
exploring. They don't teach you how to program or write games, they just 
present the tools to you and encourage you to build your own. The first six 
lessons concentrate on defining the playing field. Pay close attention!

     If you find a word being used that you do not understand, consult the 
Glossary. Once you get through the lessons, read the Glossary in detail. You'll 
find yourself understanding some of the esoterica. Some of the advanced 
features you may never use or understand and it may take awhile for you to see 
why some of the diversions from BASIC were necessary. Before long, however, you 
will find going back to BASIC unbearable.

     Just to get you started, there's a test program called NB in the system. 
Press the red RST on the UV-1 front panel and answer Y. Then type the two 
letters NB and press the RETURN key. An image will appear. Type NB and press 
RETURN again. The image will undo itself. For more action, type NB.B and press 
RETURN. You can stop this by pressing the CTRL (called CONTROL on some 
keyboards) key, holding it down and simultaneously pressing the C key. Have 
fun!

End of Lesson 0.


All Lessons:

0 - Read Me First
1 - Getting Started
2 - Writing Macros
3 - Editing
4 - More on Macros
5 - Storing Macros on Tape and Disk
6 - Debugging
7 - Device Variables and Ports
8 - Arrays
9 - More on Graphics
10 - Swap Modules
11 - Advanced Concepts