DREAM: the tool behind the fast games

Why machine code

BASIC is easy to write but slow. Machine code is direct orders to the 6809 processor: dozens of times faster, but harder. DREAM does three things: an editor to write the program, an assembler that turns it into code the processor understands, and running it straight away.

Loading from tape

First reserve some memory: CLEAR 200,12000 and ENTER. Then CLOADM, and when OK appears, type EXEC. When it asks OLD TEXT?, press N and the screen clears.

A first program

This program fills the screen with the letter A and waits for a key. Type each line followed by ENTER. A line that starts with a space must start with a space: a word at the start of a line is a label (like LOOP), and the instruction comes after a space.

@ LDX #$0400
 LDA #'A
LOOP STA ,X+
 CMPX #$0600
 BLO LOOP
KEY LDX $A000
 JSR ,X
 BEQ KEY
 RTS

What each line does

LDX #$0400 points at the start of screen memory, and the @ marks where the program starts. LDA #'A takes the letter. STA ,X+ puts it on the screen and moves one place on. CMPX #$0600 and BLO LOOP go round until the end of the screen. The next three lines check for a key press, and RTS returns to the editor.

Assemble and run

BREAK, A, ENTER	Assemble: the code appears beside each line
BREAK, X, ENTER	Run: the screen fills with A
Any key	Back to the editor
BREAK, Q, ENTER	From the assembler back to the editor, to fix errors
BREAK, T, ENTER	Back to text mode after a graphics program

A first experiment

Change 'A to another character, say '*, and run it again. This is the moment you feel how fast machine code is: the screen fills in an instant.

This guide is in our own words, for Dragon owners who have the original program. We do not host the program or its original manual. We tried every step on an emulated machine with the same chips.