Machine Language for Beginner's Part 1

In the following issues I am going  to use this as a ML For Beginners  course. By the time you finish it, you  will have enough knowledge to do  almost anything you want in ML.  Including some rudimentary special  effects as used in software pirate's  demos.

For this month we are going to go  over the most basic commands in ML,  and I will show you how to use these  to write your first ML routine.

Although most people view ML as  the 'complex' language, it is really  much simpler than BASIC. It is just  that you need a number of simple  commands to equal one command from a  high-level language such as BASIC.

First we will learn about the most  important register in ML-the  Accumulator. Different ML instructions  allow you to copy the accumulator to a  memory location and vice versa, modify  its contents, and other useful tasks.  This may not seem like much but this  is where 50% of a program is  accomplished. In addition, the  accumulator is the only register that  has math instructions.

    Now we will learn our first ML  instruction. LDA. You may have guessed  it stands for LoaD the Accumulator and  is arguably the most used of all  commands. 

Putting a '#' after LDA tells the  computer that you want to LoaD the Accumulator with the value after it.

A '$' following the LDA simply  tells the computer that the number  following is in hexadecimal form. (For  more info on HEX see the preceding 
file.)

With this knowledge you should  know that:

LDA #$05 

tells the computer to LoaD the Accumulator with $05. Make sense?  Good. This is very simple to grasp but  is required to perform many things.

Our next command is STA. It stands  for Store The Accumulator. This  command takes the value in the  accumulator and transfers it to to any  memory location you wish. 

Before we can write our first  routine we need to know one more  command. BRK. It is the Break command  and is needed because in ML, if there  is no BRK at the end-it will just lock  up.

 Now we can write our first  routine. It is very simple and changes  the screen color to Cyan.

To type it in a ML monitor you  need to follow this format.

.A 1400 LDA #$03

    The .A tells it that this is an  accumulator instruction. Afterwords,  the monitor will automatically number  and place the correct beginning on the 
lines.

.A 1402 STA $D020

    $D020 is the equivelant to 53280  in decimal.

Last but not least...

.A 1404 BRK

Now press return until you are on a  clean line and type G 1400.

Bingo! If you did everything right it  will change your screen to Cyan.

 Congratulations. You have now  created you first program. Play around  with those commands and see how much  else you can accomplish with that  little bit of info.

Unfortunatly I was in a bind for  time this issue so it is semi small, 
but next issue I will have a immense  column to help you further into the 
world of ML.