View source for Hex and Binary



==Binary==
Binary has two possible values:
*TRUE (1)
*FALSE (0)

==Hex==
Hex is base 8. Decimal, the format we use in everyday life is base 10. Base 8 is simply far more efficient for computer operations.

Binary, Hexadecimal and Decimal (unsigned) equivalents
 0x Represents an hexadecimal value

 00000000 : 0x00 : 0
 00000001 : 0x01 : 1
 00000010 : 0x02 : 2
 00000011 : 0x03 : 3
 00000100 : 0x04 : 4
 00000101 : 0x05 : 5
 00000110 : 0x06 : 6
 00000111 : 0x07 : 7
 00001000 : 0x08 : 8
 00001001 : 0x09 : 9
 00001010 : 0x0A : 10
 00001011 : 0x0B : 11
 00001100 : 0x0C : 12
 00001101 : 0x0D : 13
 00001110 : 0x0E : 14
 00001111 : 0x0F : 15
 00010000 : 0x10 : 16
 00011000 : 0x18 : 24
 00100000 : 0x20 : 32
 00110000 : 0x30 : 48
 01000000 : 0x40 : 64
 01100000 : 0x60 : 96
 10000000 : 0x80 : 128
 10100000 : 0xA0 : 160
 10110000 : 0xB0 : 176
 11000000 : 0xC0 : 192
 11010000 : 0xD0 : 208
 11100000 : 0xE0 : 224
 11110000 : 0xF0 : 240
 11111111 : 0xFF : 255

Each bit is worth twice more than the previous one. You simply add them all up to have your value in hex/decimal.

 1st bit: 1
 2nd bit: 2
 3rd bit: 4
 4th bit: 8
 5th bit: 16
 6th bit: 32
 7th bit: 64
 8th bit: 128
 and so on

==Bytes and Beyond==

Bytes, Half-Words, Words are composed of so many bits (a bit is a boolean value, TRUE or FALSE):
*Boolean: 0 or 1 (1 bit)
*Nibble: 0x0 to 0xF (4 bits)
*:unsigned: 0 to +15
*:signed: -8 to +7
*Byte: 0x00 to 0xFF (8 bits)
*:unsigned: 0 to +255
*:signed: -128 to +127
*Half-Word: 0x0000 to 0xFFFF (16 bits)
*:unsigned: 0 to +65535
*:signed: -32768 to +65535
*Word: 0x00000000 to 0xFFFFFFFF (32 bits)
*:unsigned: 0 to +4294967295
*:signed: -2147483648 to +2147483647

==Flags==
Flags are values that are usually one bit long, part of a byte, that it meant to literally be interpreted as TRUE or FALSE by the game.

For example, this byte is only composed of flags. They're technically Boolean values, but we call them flags to understand each other better:

0x??
    0x80 Male
    0x40 Female
    0x20 Monster
    0x10 Join After Event
    0x08 Load Formation
    0x04 ??? Stats
    0x02
    0x01 Save Formation

Now let's say this Byte has a value of 0x59, which in binary is 010011001 or 0x40 + 0x10 + 0x08 + 0x01. Meaning that "Female", "Join After Event", "Load Formation" and "Save Formation" are set.

==Byte Order==
Now you have to understand that MIPS r3000 will swap the bytes when handling Half-Words and Words.

What does this mean?

If the game wants to fetch a Half-Word, in the game's memory that value might be written as:
 78 5A
But because the game is trying to read a Half-Word through opcode instructions (see [[ASM Hacking]]), it will be stored in the registers as 0x00005A78. Registers are 32bit and are used to hold values that will be computed by the game. They are loaded, altered, compared, and saved back as necessary.

Similarly, if the game wanted to load a Word:
 9C B5 06 80
The value loaded would be 0x8006B59C.

Now if you see these values in the game's memory through a Hex Editor or an emulator's Memory Viewer:
 59 00 C8 00 74 01 66 01 12 00 B7 01 32 00
You can simply guess the format and say those all look like Half-Words, you'd likely be right. But be careful, it depends on the way the game loads and saves values that determines if they are Bytes/Half-Words/Words, and not what you, yourself see in just Hex.

==Unsigned VS signed==
Again, this is determined by the game's code. Unless you can figure it out through the game's code or through logic, you cannot tell if a value is signed or unsigned.
0xC0 can be +192 (unsigned) or -64 (signed)
0xFFF8 can be +65528 (unsigned) or -8 (signed)

*Bytes:
*:Lowest unsigned value: 0x00 (0)
*:Highest unsigned value: 0xFF (+255)
*:Lowest unsigned value: 0x80 (-128)
*:Highest unsigned value: 0x7F (+127)
*Half-Words:
*:Lowest unsigned value: 0x0000 (0)
*:Highest unsigned value: 0xFFFF (+65535)
*:Lowest unsigned value: 0x8000 (-32768)
*:Highest unsigned value: 0x7FFF (+32767)
*Half-Words:
*:Lowest unsigned value: 0x00000000 (0)
*:Highest unsigned value: 0xFFFFFFFF (+4294967295)
*:Lowest unsigned value: 0x80000000 (-2147483648)
*:Highest unsigned value: 0x7FFFFFFF (+2147483647)

Half the values are negative and the other half are positive when dealing with signed values (0 being positive).

Signed Values
 0x80000000 = -2147483648
 0xFF000000 = -16777216
 0xFFFF0000 = -65536
 0xFFFFFF00 = -256
 0xFFFFFFF8 = -8
 0xFFFFFFFF = -1
 0x00000000 = 0
 0x00000008 = +8
 0x000000FF = +255
 0x0000FFFF = +65535
 0x00FFFFFF = +16777215
 0x7FFFFFFF = +2147483647