The Hex Files

Ferris The Hex Files Programmer at work - part 3 by Ferris Welcome again, and before we start I'll just give you the solution to the little teaser I posed at the end of the previous article. The modified routine should look like this: *= $0900 LDX #$00 LDA #$03 To change the character LOOP STA $0400,X INX CPX #$0B To change the number of repeats BNE LOOP RTS Okay, lets have some fun with a loop shall we? One of the most common things in demos (and in fact most games too) is the scrolling message and what we are going to do is a simple one with some limits. As we have seen from the example last issue it's possible to put characters on the...

Ferris The Hex Files Programmer at work - part 2 by Ferris Hello all and welcome to the second part of our course for budding programmers. Last issue we introduced a few of the commands our C64 can understand and this issue I intend to bring a few more in to play. LDA and LDX have both been covered independently last issue, but they can work together. Lets get things off to a start with the first example: LDX #$00 Set the X register to zero. LDA #$01 Set the A register as well. STA $0400,X Store A to $0400+X. RTS Exit. If we were to run this a letter A would appear at the top left corner of our screen. Nothing exiting so far eh? Well, if...

Ferris The Hex Files Programmer at work - part 1 by Ferris A lot of people out there have expressed an interest in learning machine code. And after all, if you want to write successful games, demos or utilities it is the best language to learn, albeit a bit unfriendly. The main problem with machine code is its simplicity. There, I bet that confused you a bit eh? What I mean is that almost anything can be done in a single BASIC command can take a bit more work in machine language but at a greatly increased speed. Right, that's the intro over with so lets start looking at some commands. The first one I've decided to explain is RTS. RTS is ...