Hex and Binary

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Binary and Hexadecimal (sometimes abbreviated to hex) are alternative numeral systems. Decimal, the everyday numeral system, is base 10, meaning that each digit represents 10 times the value of the digit to its right.

Overview

Binary is base 2, while hexadecimal is base 16. So "10" represents ten in decimal, but it represents 2 in binary, and 16 in hexadecimal.

Digits Binary Decimal Hexadecimal
"1" 1 1 1
"10" 2 10 16
"100" 4 100 256
"1000" 8 1000 4096
"10000" 16 10000 65536
"100000" 32 100000 1048576
"1000000" 64 1000000 16777216
"10000000" 128 10000000 268435456
"100000000" 256 100000000 4294967296
"1000000000" 512 1000000000 68719476736
"10000000000" 1024 10000000000 1099511627776


Binary

Binary is the basic representation for computers, because electric transistors can have (close to) zero charge or (close to) high charge.

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

Hexadecimal

Hexadecimal is used in programming instead of decimal because each hexadecimal digit expands exactly to four binary digits. Conversion between decimal and binary is much more complicated.

Hexadecimals on this wiki are usually either prefixed with "0x" or suffixed with "h". For example, "0x8F" or "8Fh".

The hexadecimal digits are (lowercase or uppercase):

Hex Decimal Binary
0 0 0
1 1 1
2 2 10
3 3 11
4 4 100
5 5 101
6 6 110
7 7 111
8 8 1000
9 9 1001
A 10 1010
B 11 1011
C 12 1100
D 13 1101
E 14 1110
F 15 1111


Binary, Hexadecimal and Decimal (unsigned) equivalents

Binary Hexadecimal Decimal
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

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 signed value: 0x80 (-128)
    Highest signed value: 0x7F (+127)
  • Half-Words:
    Lowest unsigned value: 0x0000 (0)
    Highest unsigned value: 0xFFFF (+65535)
    Lowest signed value: 0x8000 (-32768)
    Highest signed value: 0x7FFF (+32767)
  • Half-Words:
    Lowest unsigned value: 0x00000000 (0)
    Highest unsigned value: 0xFFFFFFFF (+4294967295)
    Lowest signed value: 0x80000000 (-2147483648)
    Highest signed 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