By FelixWright and Nodever2
Hello, and welcome to our current guide for HxD and hex editing in general.
The main goal of this guide is to teach newbies how to edit ROMs with hexadecimal.
Let's get started.
HxD is a hex editor, disk editor, and memory editor developed for Windows. HxD can open files larger than 4 GiB and open and edit the raw contents of disk drives, as well as display and edit the memory used by running processes. Among other features, it can calculate various checksums, compare files, or shred files. The most recent version was created in 2009 by Maël Hörz.
HxD 2.0 RC can be downloaded from mh-nexus.
What is Hexadecimal?
To understand hexadecimal, you need to understand decimal. Decimal (also called base-ten, and occasionally called denary) is the standard system for denoting integer and non-integer numbers. Decimal is called base10 because it uses ten values: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9. Because it is the de-facto standard number system, it does not have any denotation.
Example: 100 in Decimal is 100.
Hexadecimal is a positional numeral system with a radix, or base, of 16. This means it uses sixteen symbols, in this case 0–9 to represent values zero to nine, and A–F to represent values ten to fifteen. In the romhacking scene, hex values are denoted with $ or 0x. Less commonly, you may also see a hexadecimal number denoted by a trailing h, although it is not recommended to write it this way yourself unless you know what you're doing, as it is lesser known.
Example: 100 in Hexadecimal is $64, 0x64, or less commonly, 64h.
More examples:
DECIMAL = 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 HEX = 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 1F
There are many online resources for converting hex to decimal, but in this tutorial I will explain how to convert hex to decimal and decimal to hex using windows calculator. Before we begin, run calc.exe and press Alt + 3. This will put the calculator in programming mode.
Select the “Hex” Bubble.
Paste in your hex value (Ctrl + V) or type it in. Select the “Dec” Bubble.
Ctrl + C to copy converted value to clipboard.
Select the “Dec” Bubble.
Paste in your dec value (Ctrl + V) or type it in. Select the “Hex” Bubble.
Ctrl + C to copy converted value to clipboard.
Keyboard Shortcuts
Before we get into hex editing you should learn keyboard shortcuts. For ROMHacking, here's what you will need to know:
| Key Combination | Description |
|---|---|
| F3 | Find Again |
| F6 | Next Difference (File Compare) |
| Delete | Clear Selection (Note: This shortens filesize!) |
| CTRL + A | Select All |
| CTRL + E | Select Block… |
| CTRL + G | Go To… |
| CTRL + K | File Compare… |
| CTRL + N | New file (Empty) |
| CTRL + C | Copy Selection |
| CTRL + X | Cut Selection |
| CTRL + V | Paste Insert (Note: This increases filesize!) |
| CTRL + B | Paste Write (Overwrite) |
| CTRL + Z | Undo |
| CTRL + Y | Redo |
| CTRL + O | Open a file… |
| CTRL + R | Find & Replace… |
| CTRL + S | Save a file |
| Shift + F3 | Find Again (Reverse) |
| Shift + F6 | Previous Difference (File Compare) |
| Ctrl + F4/Ctrl + W | Close file |
| Ctrl+Number (0-9) | Goto bookmark |
| Ctrl+Shift+Number (0-9) | Add bookmark |
| Left and Right Arrow keys | Move to next/previous byte |
| Up and Down Arrow keys | Move to next/previous row |
| Shift + Up/Shift + Down | Select next/previous row |
| Shift + Left/Shift + Right | Select next/previous byte |
WARNING: Changes in filesize could destroy your ROM if you're not careful!
Going forward, Let's say you want to disable the low energy alarm in Zero Mission. 0x52888 = 1D 2F to 14 E0
Open Zero Mission in HxD, and use Goto… (Ctrl + G)
As you can see, by default HxD assumes you want to put in a hex address, and the address above is hex so that is fine. If you run into a decimal or octal address though, you can select the dec or oct bubbles and then paste in the address.
So we're at address 0x52888. The text cursor should be blinking to the left of 1D. Select 1D, and type 14. Your cursor should now be blinking to the left of 2F. Select 2F, and replace it with E0. Save your changes with Ctrl + S. You have just performed a hex tweak! Open your ROM in an emulator, and reduce samus' energy below 30. There should no longer be a low energy alarm.
SNES roms are divided into banks, which are $8000 bytes long (32,768 bytes in decimal). Super Metroid is of the rom type LoROM, so it can address banks from bank $80-$FF. Because HxD uses PC addresses, and the majority of documentation for SNES games is written with SNES addresses, it's important to know the distinction between the two. PC addresses start at $000000, while SNES addresses start at $80:8000. Every SNES bank starts at $XX:8000, where XX is the bank number. The game reads addresses in this LoROM format. In a LoROM address, the bank is number separated by a colon.
Examples:
| PC address | SNES address |
|---|---|
| $4000 | $80:C000 |
| $9500 | $81:0500 |
| $791F8 | $8F:91F8 |
| $7FFFF | $8F:FFFF |
Looking at the LoROM addresses, we can see these addresses are referring to locations in banks 80, 81, 8F, and 8F (again), respectively.
It is not necessarily important to know how to convert between PC and LoROM addresses, since there is a program called Lunar Address which is highly recommended to use for this purpose; it's just important to understand the difference.
To know at a glance whether or not an address is a SNES or PC address, know that Super Metroid, as well as just about every other SNES game, never comes close to reaching $80:8000 in PC, so any address starting there or beyond is very likely a SNES address. List of SM's Banks at a Glance
From the SMMM:
Bank $## LoROM address PC address Bank description
---------------------------------------------------------------------------------------------------------------------
Bank $80 $80:0000-$80:7FFF $0-7FFF Game setup, intros, save station data, other important stuff.
Bank $81 $81:8000-$81:FFFF $8000-FFFF Map data, save data, sprite drawing routines, etc.
Bank $82 $82:0000-$82:7FFF $10000-17FFF Load areas, pause data, game states, HDMA, demo setup, Samus dying, room setup, etc.
Bank $83 $83:8000-$83:FFFF $18000-1FFFF FX Data, door data, FX 'Animated Tiles' and 'Palette Setup' setup.
Bank $84 $84:0000-$84:7FFF $20000-27FFF PLM setup, PLM data, probably other stuff.
Bank $85 $85:8000-$85:FFFF $28000-2FFFF Message boxes from PLMs and Samus's ship.
Bank $86 $86:0000-$86:7FFF $30000-37FFF Enemy projectiles, enemy drops setup.
Bank $87 $87:8000-$87:FFFF $38000-3FFFF FX graphics, golden boss statue graphics.
Bank $88 $88:0000-$88:7FFF $40000-47FFF DMA/HDMA stuff, power bomb explosions, Crateria scrolling sky, etc.
Bank $89 $89:8000-$89:FFFF $48000-4FFFF Item graphics, palette blends, FX color math stuff.
Bank $8A $8A:0000-$8A:7FFF $50000-57FFF FX tilemaps, free space.
Bank $8B $8B:8000-$8B:FFFF $58000-5FFFF Screen fades, OAM stuff, title setup, ending and credits stuff, etc.
Bank $8C $8C:0000-$8C:7FFF $60000-67FFF Intro & menu tilemaps, ending tilemaps, etc.
Bank $8D $8D:8000-$8D:FFFF $68000-6FFFF FX palettes, cheat for damage in heated rooms, etc.
Bank $8E $8E:0000-$8E:7FFF $70000-77FFF Main menu palettes and graphics, etc.
Bank $8F $8F:8000-$8F:FFFF $78000-7FFFF Room headers, PLM Set data, Background data, Room Scrolls data, etc.
Bank $90 $90:0000-$90:7FFF $80000-87FFF Samus's animations/movement/weapons, shinesparking, minimap, hitbox collision, etc.
Bank $91 $91:8000-$91:FFFF $88000-8FFFF Samus's movement transitions/frame delays, other Samus data, demo inputs, etc.
Bank $92 $92:0000-$92:7FFF $90000-97FFF Animation pointer tables, animation data, tilemaps, etc.
Bank $93 $93:8000-$93:FFFF $98000-9FFFF Samus's beam animation tilemaps.
Bank $94 $94:0000-$94:7FFF $A0000-A7FFF BTS collision, start of "Special GFX" in SMILE.
Bank $95 $95:8000-$95:FFFF $A8000-AFFFF "Special GFX" in SMILE.
Bank $96 $96:0000-$96:7FFF $B0000-B7FFF "Special GFX" in SMILE.
Bank $97 $97:8000-$97:FFFF $B8000-BFFFF "Special GFX" in SMILE.
Bank $98 $98:0000-$98:7FFF $C0000-C7FFF "Special GFX" in SMILE.
Bank $99 $99:8000-$99:FFFF $C8000-CFFFF "Special GFX" in SMILE.
Bank $9A $9A:0000-$9A:7FFF $D0000-D7FFF Grapple graphics, layer FX graphics, beam graphics, common sprite graphics, etc.
Bank $9B $9B:8000-$9B:FFFF $D8000-DFFFF Samus's graphics.
Bank $9C $9C:0000-$9C:7FFF $E0000-E7FFF Samus's graphics.
Bank $9D $9D:8000-$9D:FFFF $E8000-EFFFF Samus's graphics.
Bank $9E $9E:0000-$9E:7FFF $F0000-F7FFF Samus's graphics.
Bank $9F $9F:8000-$9F:FFFF $F8000-FFFFF Samus's graphics.
Bank $A0 $A0:0000-$A0:7FFF $100000-107FFF Lots of common enemy routines, enemy header data, free space.
Bank $A1 $A1:8000-$A1:FFFF $108000-10FFFF Enemy GFX pointer data, free space.
Bank $A2 $A2:0000-$A2:7FFF $110000-117FFF Enemy AI.
Bank $A3 $A3:8000-$A3:FFFF $118000-11FFFF Enemy AI.
Bank $A4 $A4:8000-$A4:7FFF $120000-127FFF Enemy AI.
Bank $A5 $A5:8000-$A5:FFFF $128000-12FFFF Enemy AI.
Bank $A6 $A6:8000-$A6:7FFF $130000-137FFF Enemy AI.
Bank $A7 $A7:8000-$A7:FFFF $138000-13FFFF Enemy AI.
Bank $A8 $A8:8000-$A8:7FFF $140000-147FFF Enemy AI.
Bank $A9 $A9:8000-$A9:FFFF $148000-14FFFF Enemy AI.
Bank $AA $AA:8000-$AA:7FFF $150000-157FFF Enemy AI.
Bank $AB $AB:8000-$AB:FFFF $158000-15FFFF Enemy AI.
Bank $AC $AC:8000-$AC:7FFF $160000-167FFF Enemy graphics.
Bank $AD $AD:8000-$AD:FFFF $168000-16FFFF Enemy graphics.
Bank $AE $AE:8000-$AE:7FFF $170000-177FFF Enemy graphics.
Bank $AF $AF:0000-$AF:FFFF $178000-17FFFF Enemy graphics.
Bank $B0 $B0:0000-$B0:7FFF $180000-187FFF Enemy graphics.
Bank $B1 $B1:8000-$B1:FFFF $188000-18FFFF Enemy graphics.
Bank $B2 $B2:0000-$B2:7FFF $190000-197FFF Space pirate hitboxes, also tilemaps(?), etc.
Bank $B3 $B3:8000-$B3:FFFF $198000-19FFFF Miscellaneous enemy/boss stuff (i.e, Botwoon's destroyed wall), etc.
Bank $B4 $B4:0000-$B4:7FFF $1A0000-1A7FFF Enemy Set pointer data, debug stuff, enemy instructions/weaknesses/drops.
Bank $B5 $B5:8000-$B5:FFFF $1A8000-1AFFFF Area map tilemaps, free space.
Bank $B6 $B6:0000-$B6:7FFF $1B0000-1B7FFF Graphics and tilemaps for the equipment/map/title screens.
Bank $B7 $B7:8000-$B7:FFFF $1B8000-1BFFFF Enemy graphics (Tourian enemies, Botwoon, etc.)
Bank $B8 $B8:0000-$B8:7FFF $1C0000-1C7FFF Free space (unused bank).
Bank $B9 $B9:8000-$B9:FFFF $1C8000-1CFFFF CRE graphics/table, Background pointer tilemaps.
Bank $BA $BA:0000-$BA:7FFF $1D0000-1D7FFF Background pointer tilemaps, tileset graphics.
Bank $BB $BB:8000-$BB:FFFF $1D8000-1DFFFF Tileset graphics.
Bank $BC $BC:0000-$BC:7FFF $1E0000-1E7FFF Tileset graphics.
Bank $BD $BD:8000-$BD:FFFF $1E8000-1EFFFF Tileset graphics.
Bank $BE $BE:0000-$BE:7FFF $1F0000-1F7FFF Tileset graphics.
Bank $BF $BF:8000-$BF:FFFF $1F8000-1FFFFF Tileset graphics.
Bank $C0 $C0:0000-$C0:7FFF $200000-207FFF Tileset graphics.
Bank $C1 $C1:8000-$C1:FFFF $208000-20FFFF Tileset graphics, tileset tables, etc.
Bank $C2 $C2:0000-$C2:7FFF $210000-217FFF Tileset tables, tileset palettes, level data.
Bank $C3 $C3:8000-$C3:FFFF $218000-21FFFF Level data.
Bank $C4 $C4:0000-$C4:7FFF $220000-227FFF Level data.
Bank $C5 $C5:8000-$C5:FFFF $228000-22FFFF Level data.
Bank $C6 $C6:0000-$C6:7FFF $230000-237FFF Level data.
Bank $C7 $C7:8000-$C7:FFFF $238000-23FFFF Level data.
Bank $C8 $C8:0000-$C8:7FFF $240000-247FFF Level data.
Bank $C9 $C9:8000-$C9:FFFF $248000-24FFFF Level data.
Bank $CA $CA:0000-$CA:7FFF $250000-257FFF Level data.
Bank $CB $CB:8000-$CB:FFFF $258000-25FFFF Level data.
Bank $CC $CC:0000-$CC:7FFF $260000-267FFF Level data.
Bank $CD $CD:8000-$CD:FFFF $268000-26FFFF Level data.
Bank $CE $CE:0000-$CE:7FFF $270000-277FFF Level data.
Bank $CF $CF:8000-$CF:FFFF $278000-27FFFF Music/audio setup.
Bank $D0 $D0:0000-$D0:7FFF $280000-287FFF Music data.
Bank $D1 $D1:8000-$D1:FFFF $288000-28FFFF Music data.
Bank $D2 $D2:0000-$D2:7FFF $290000-297FFF Music data.
Bank $D3 $D3:8000-$D3:FFFF $298000-29FFFF Music data.
Bank $D4 $D4:0000-$D4:7FFF $2A0000-2A7FFF Music data.
Bank $D5 $D5:8000-$D5:FFFF $2A8000-2AFFFF Music data.
Bank $D6 $D6:0000-$D6:7FFF $2B0000-2B7FFF Music data.
Bank $D7 $D7:8000-$D7:FFFF $2B8000-2BFFFF Music data.
Bank $D8 $D8:0000-$D8:7FFF $2C0000-2C7FFF Music data.
Bank $D9 $D9:8000-$D9:FFFF $2C8000-2CFFFF Music data.
Bank $DA $DA:0000-$DA:7FFF $2D0000-2D7FFF Music data.
Bank $DB $DB:8000-$DB:FFFF $2D8000-2DFFFF Music data.
Bank $DC $DC:0000-$DC:7FFF $2E0000-2E7FFF Music data.
Bank $DD $DD:8000-$DD:FFFF $2E8000-2EFFFF Music data.
Bank $DE $DE:0000-$DE:7FFF $2F0000-2F7FFF Music data.
Bank $DF $DF:8000-$DF:FFFF $2F8000-2FFFFF Unused songs, note length table, ASDR settings, tracker, etc.
Banks $E0-FF must be added by SMILE ("ROM" > "Expand ROM") before they can be seen in a hex editor.
Bank $E0 $E0:0000-$E0:7FFF $300000-307FFF Free space
Bank $E1 $E1:8000-$E1:FFFF $308000-30FFFF Free space
Bank $E2 $E2:0000-$E2:7FFF $310000-317FFF Free space
Bank $E3 $E3:8000-$E3:FFFF $318000-31FFFF Free space
Bank $E4 $E4:0000-$E4:7FFF $320000-327FFF Free space
Bank $E5 $E5:8000-$E5:FFFF $328000-32FFFF Free space
Bank $E6 $E6:0000-$E6:7FFF $330000-337FFF Free space
Bank $E7 $E7:8000-$E7:FFFF $338000-33FFFF Free space
Bank $E8 $E8:0000-$E8:7FFF $340000-347FFF Free space
Bank $E9 $E9:8000-$E9:FFFF $348000-34FFFF Free space
Bank $EA $EA:0000-$EA:7FFF $350000-357FFF Free space
Bank $EB $EB:8000-$EB:FFFF $358000-35FFFF Free space
Bank $EC $EC:0000-$EC:7FFF $360000-367FFF Free space
Bank $ED $ED:8000-$ED:FFFF $368000-36FFFF Free space
Bank $EE $EE:0000-$EE:7FFF $370000-377FFF Free space
Bank $EF $EF:8000-$EF:FFFF $378000-37FFFF Free space
Bank $F0 $F0:0000-$F0:7FFF $380000-387FFF Free space
Bank $F1 $F1:8000-$F1:FFFF $388000-38FFFF Free space
Bank $F2 $F2:0000-$F2:7FFF $390000-397FFF Free space
Bank $F3 $F3:8000-$F3:FFFF $398000-39FFFF Free space
Bank $F4 $F4:0000-$F4:7FFF $3A0000-3A7FFF Free space
Bank $F5 $F5:8000-$F5:FFFF $3A8000-3AFFFF Free space
Bank $F6 $F6:0000-$F6:7FFF $3B0000-3B7FFF Free space
Bank $F7 $F7:8000-$F7:FFFF $3B8000-3BFFFF Free space
Bank $F8 $F8:0000-$F8:7FFF $3C0000-3C7FFF Free space
Bank $F9 $F9:8000-$F9:FFFF $3C8000-3CFFFF Free space
Bank $FA $FA:0000-$FA:7FFF $3D0000-3D7FFF Free space
Bank $FB $FB:8000-$FB:FFFF $3D8000-3DFFFF Free space
Bank $FC $FC:0000-$FC:7FFF $3E0000-3E7FFF Free space
Bank $FD $FD:8000-$FD:FFFF $3E8000-3EFFFF Free space
Bank $FE $FE:0000-$FE:7FFF $3F0000-3F7FFF Free space
Bank $FF $FF:8000-$FF:FFFF $3F8000-3FFFFF Free space