So you want to be a ROM Hacker? Now's a great time to learn. We're at what is most likely the tail end of the SNES hacking era. Things are only going to get more complicated from here. If you intend on getting in on the fun the 32 bit era promises, learning the 16 bit basics now would probably be a good idea.

What I'll be doing over the next few weeks is writing a tutorial while hacking Genjuo Ryodan. At the moment I don't intend to do a full translation of the game. If some random good samaritan from Japan who is fluent in Japanese and English decides to offer his or her assistance, I would be extremely grateful, but I won't be actively seeking a translator. Instead, I'll be releasing all my work as I go along, and perhaps someone will decide to contribute. Yes, basically, this is an "open source" translation project.

Getting Started:

Acquire the following:

Naga
Hexecute
Hex Workshop
Genjuo Ryodan Rom

We won't be using all of these right now however. This week we'll be going over the basics. The VERY basics. Many of you will want to go read cnn or something until next week when we'll be getting into the "fun" stuff. The rest of you who are absolute newbies will want to pay close attention to what follows.

The Basics of Bases

How many fingers is the normal human child born with? 10.

How many fingers is your computer born with? uh.... ?

Believe it or not, your computer does not count with the same number system you do. Neither do consoles. Unless you're in posession of a Setun computer or some such, your computer counts using two numbers. 0 and 1. On and Off. This my friends, is called the Binary Number System. You will NEED to know how to convert between binary and decimal numbers if you intend on getting down and dirty in some hot and heavy hacking action.

So how does this mysterious numbering system work?

It's easy as pie my friends.

Do you remember in grade school going over the difference between the ones, tens, and hundreds place in math class? They'd draw these little boxes to help you count and identify how many hundreds there were in 347. Binary works the same way. You've got different places, and the places matter. Big time. Just like you can't reorder 347 to 437 and have it be the same number, you cant just move around binary numbers and have them hold the same meaning. Lets look at the decimal number 205 in binary.

As the above diagram shows, 8 binary digits are used to represent the number 205. The binary digits, just like the decimal numbers you're used to, go from left to right with the digit with the greatest value to the left and the smallest value on the right.

This brings us to an important excersize. Exactly how do you convert between decimal and binary?

Well, first off, lets go from binary to decimal. See that binary number in that graphic above? 11001101. As the graphic shows, each of those binary "bits" or digits equates to a decimal number. The value to the far left equates to 128 or 2 raised to the 7th power in exponential notation. In fact, each of those binary digits equates to a power of 2. That's why it's called the "Binary" system. Bi being a prefix meaning 2 (Dec coincidentally is the prefix for 10 even though December is the 12th month of the year. For this we have a bunch of pompus Roman Emperors to thank. Yay Augustus and Julius!). In any case, to convert binary numbers to decimal numbers, we work from the right to the left, multiplying the binary digit by a power of 2. Here's how it works out in this case:

1*1=1
0*2=0
1*4=4
1*8=8
0*16=0
0*32=0
1*64=64
1*128=128

Now we add the numbers togeather.

1+4+8+64+128=205

Wow! What a suprise! 205. Who would have predicted that number would result from that string of binary bits! Now that I'm done being a sarcastic smartass, lets learn how to convert 205 back into binary. Pretend like you don't know the answer. It's more fun that way.

To figure out what the binary representation is of a decimal number, we're going to have to devide by 2 until we hit 0, paying particular attention to remainders and ignoring any numbers after the decimal place that result from our division, as such:

205/2=102 remainder 1
102/2=51 remainder 0
51/2=25 remainder 1
25/2=12 remainder 1
12/2=6 remainder 0
6/2=3 remainder 0
3/2=1 remainder 1
1/2=0 remainder 1

Now we read the remainders from the bottom of the list to the top and write them left to right, as such:

11001101

Low and behold, we're back where we started!

Well, what about hexadecimal. I always here some random loser romhacker talking about hexadecimal. How does that work?

Yo, dis shit id phat. It be da bomb yo.

Hexadecimal is rather easy. Before we get into converting back and forth between decimal and hex, let me introduce you to the new way of counting. Ever hear of new math? This is nothing like that.

0 1 2 3 4 5 6 7 8 9 A B C D E F. Those right there are your new numbers. Learn them well and never forget them. How about we count in hexadecimal up to 30 and watch the progression of numbers.

0 1 2 3 4 5 6 7 8 9 A B C D E F 10 11 12 13 14 15 16 17 18 19 1A 1B 1C 1D 1E

Well now. That wasn't too hard, was it. What? You don't believe me that 1E is 30 (even if you do, please play along. It makes this so much more fun)? Lets convert 1E to decimal and find out. Converting hexadecimal to decimal is done pretty much the same way converting binary to hexadecimal was done.

1E

The digit on the far right is said to be in the "0's place" and the digit to the left of the 0 is in the "1's place". Just like we did with the binary conversion, we're going to be multiplying by a power of some number. What would that number be here? In the case of binary (base 2) it was 2. So in the case of hexadecimal (base 16), I suppose it would be 16, ne?

E * 16^0

1 * 16^1

E is the hexadecimal equivalent of 14. (A=10, B=11, C=12, ...) Anything to the 0 power is 1. And anything to the 1st power is itself. Therefore:

14*1=14

1*16=16

16+14=30. Tada. Ladies and gentlemen, we have just converted a hexadecimal number to decimal! Yay for us.

Well now, how would I convert a decimal number to hexadecimal? How about we try that division stuff that worked so well before for binary? Sounds like a plan to me. Lets try again with 30.

30/16=1 Remainder 14
1/16=0 Remainder 1

Now we read from the bottom up, remembering to convert remainders larger than 9 to their Hexadecimal digit equivalents. So we've got 1 and 14 which is E. 1E. Yay. Another successful conversion!

Tune in next week for a rousing lesson on fonts where we'll actually get into hacking Genjuo Ryodan.