Game Genie code format

Here is the decryption process for game genie codes so once you decrypt a game save you know what to change. All the known game codes are at game genie's web site.

Standard Code types 0/1/2: Write Code

0TXXXXXX 000000YY
1TXXXXXX 0000YYYY
2TXXXXXX YYYYYYYY
  XXXXXX = Address / Offset to write to
               YY = 8-Bit value to write
             YYYY = 16-Bit value to write
         YYYYYYYY = 32-Bit value to write
 T = Offset Type
     0 = From start of the data
     8 = From found from a search

Code Type 3: Increase / Decrease Code

3TXXXXXX YYYYYYYY
 XXXXXX  = Address
         YYYYYYYY = Bytes to Add/Sub
 T = Byte Value & Offset Type
     0 = Add 1 Byte  000000YY
     1 = Add 2 Bytes 0000YYYY
     2 = Add 4 Bytes YYYYYYYY
     4 = Sub 1 Byte  000000YY
     5 = Sub 2 Bytes 0000YYYY
     6 = Sub 4 Bytes YYYYYYYY
     8 = Offset from Pointer; Add 1 Byte  000000YY
     9 = Offset from Pointer; Add 2 Bytes 0000YYYY
     A = Offset from Pointer; Add 4 Bytes YYYYYYYY
     C = Offset from Pointer; Sub 1 Byte  000000YY
     D = Offset from Pointer; Sub 2 Bytes 0000YYYY
     E = Offset from Pointer; Sub 4 Bytes YYYYYYYY

Code Type 4: Multi Write/Value

4TXXXXXX YYYYYYYY
4NNNWWWW VVVVVVVV
  XXXXXX = Address / Offset from Pointer
         YYYYYYYY = Bytes to Write / 8/16/32-Bit value
 NNN = Number of times to repeat Write
    WWWW = Increases address by (in bytes)
         VVVVVVVV = Increases value by
 T = Bit Size of YYYYYYYY
     0 =  8-Bit Address / Start of the data
     1 = 16-Bit Address / Start of the data
     2 = 32-Bit Address / Start of the data
     8 =  8-Bit Pointer / Offset from a search; 1 Byte  (Writes 000000YY)
     9 = 16-Bit Pointer / Offset from a search; 2 Bytes (Writes 0000YYYY)
     A = 32-Bit Pointer / Offset from a search; 4 Bytes (Writes YYYYYYYY)

Code Type 5: Copy/Paste Bytes

5TXXXXXX ZZZZZZZZ
5TYYYYYY 00000000
  XXXXXX = Offset to copy from
  YYYYYY = Offset to copy to / Paste bytes
         ZZZZZZZZ = Number of bytes to copy
 T = Offset Type
     0 = Address / Start of the data
     8 = Pointer / Offset from a search

Code Type 6: Pointer codes

6TWX0Y0Z VVVVVVVV
 T = Data size of VVVVVVVV
     0 =  8-Bit Address / Start of the data
     1 = 16-Bit Address / Start of the data
     2 = 32-Bit Address / Start of the data
     8 =  8-Bit Pointer / Offset from a search; 1 Byte  (Writes 000000YY)
     9 = 16-Bit Pointer / Offset from a search; 2 Bytes (Writes 0000YYYY)
     A = 32-Bit Pointer / Offset from a search; 4 Bytes (Writes YYYYYYYY)
  W = operator:
      0  = Read "address" from file
      1X = Move pointer from obtained address ?? (X = 0:add, 1:substract, 2:multiply)
      2X = Move pointer ?? (X = 0:add, 1:substract, 2:multiply)
      4X = Write value: X=0 at read address, X=1 at pointer address
     Y = flag relative to read add (very tricky to understand)
       Z = flag relative to current pointer (very tricky to understand)
         VVVVVVVV = Data

Code Type 7: Add Write

7TXXXXXX YYYYYYYY = Add Write (T: 0=1byte/1=2byte/2=4byte)
 T = Bit Size
     0 = 8 bit (1 byte)
     1 = 16 bit (2 bytes)
     2 = 32 bit (4 bytes)
  XXXXXX = Address
         YYYYYYYY = Value to add

Code Type 8: Search / Pointer Command (Use Bytes to Search with)

8TFFGGGG HHHHHHHH
 T = Offset Type
     0 = Normal
     8 = Offset from Pointer (Can essentially stack pointers)
  FF = Amount of Times to Find until Write
    GGGG = Size of data to be found
         HHHHHHHH = Raw data to search for, use Multiple Lines if Needed

This command is followed by another pointer command (08*, 18*, 28*, 58*, 48*, 49*, 4A*, 9*, A8*, etc)

Example 1:

80030002 FFFF0000 - Searches for 2 bytes FFFF Three Times Until Writes
18000000 00007FFF - After the Searched Value is Found, Replaces FFFF with 7FFF

Example 2:

80040006 FFFF0000 - Searches for 6 bytes FFFF0000FFFF Four Times Until Writes
FFFF0000 00000000 - Search Code Extended
4A000000 7F7F7F7F - After the Searched Value is Found, Writes 4 bytes 7F7F7F7F two times
40020008 00000000 - Multi Code 2nd line - repeat 2 times, increase address by 8, increase value by 0

Code Type 9: Pointer Manipulator

9Y000000 XXXXXXXX
 Y = Operator
     0 = Move pointer to offset in address XXXXXXXXX
     2 = Step forward
     3 = Step backward
     4 = Step back from end of file
         XXXXXXXX = Amount to Offset

Put this after the Pointer Commands (8*, C*) and it will offset from the Pointer.

Code Type A: Mass Byte Write

ATXXXXXX YYYYYYYY
ZZZZZZZZ ZZZZZZZZ
 T = Offset Type
     0 = Address
     8 = Offset from Pointer
  XXXXXX = Writes to this Address
         YYYYYYYY = Amount of Bytes to Write
  Z = Bytes to Write (GOES FROM LEFT TO RIGHT, Does Not Flip the Values)

Example:

A0004510 0000000F - Write 15 bytes to address 4510
11223344 55667788 - First 8 bytes to Write
99AABBCC DDEEFF00 - Remaining 7 bytes to Write

Code Type C: Search / Pointer Command 2: (Use Bytes from Offset to Search with)

CTFFGGGG HHHHHHHH
 T = Offset Type
     0 = Search Forwards from Address Given
     4 = Search Backwards from Address Given
     8 = Offset from Pointer; Search Forwards from Address Given
     C = Offset from Pointer; Search Backwards from Address Given
  FF = Amount of Times to Find until Write
    GGGG = Amount of Bytes to Search
         HHHHHHHH = Bytes to Search, use Multiple Lines if Needed