These are parts of the code that do not work *incorrectly*, like [bugs and glitches](/docs/bugs_and_glitches.md), but that clearly exist just to work around a problem. In other words, with a slightly different design, the code would not need to exist at all. Design flaws may be exceptions to a usual rule, such as "tables of pointers in different banks use `dba`" ([one exception](#pic-banks-are-offset-by-pics_fix), [and another](#pokédex-entry-banks-are-derived-from-their-species-ids)) or "graphics used as a unit are stored and loaded contiguously" ([a notable exception](#footprints-are-split-into-top-and-bottom-halves)).
- [Pic banks are offset by `PICS_FIX`](#pic-banks-are-offset-by-pics_fix)
- [`PokemonPicPointers` and `UnownPicPointers` are assumed to start at the same address](#pokemonpicpointers-and-unownpicpointers-are-assumed-to-start-at-the-same-address)
- [Footprints are split into top and bottom halves](#footprints-are-split-into-top-and-bottom-halves)
- [Pokédex entry banks are derived from their species IDs](#pokédex-entry-banks-are-derived-from-their-species-ids)
- [`ITEM_C3` and `ITEM_DC` break up the continuous sequence of TM items](#item_c3-and-item_dc-break-up-the-continuous-sequence-of-tm-items)
[data/pokemon/pic_pointers.asm](/data/pokemon/pic_pointers.asm), [data/pokemon/unown_pic_pointers.asm](/data/pokemon/unown_pic_pointers.asm), and [data/trainers/pic_pointers.asm](/data/trainers/pic_pointers.asm) all have to use `dba_pic` instead of `dba`. This is a macro in [macros/data.asm](/macros/data.asm) that offsets banks by `PICS_FIX`:
```asm
dba_pic: MACRO ; dbw bank, address
db BANK(\1) - PICS_FIX
dw \1
ENDM
```
The offset is translated into a correct bank by `FixPicBank` in [gfx/load_pics.asm](/gfx/load_pics.asm):
## Pokédex entry banks are derived from their species IDs
`PokedexDataPointerTable` in [data/pokemon/dex_entry_pointers.asm](/data/pokemon/dex_entry_pointers.asm) is a table of `dw`, not `dba`, yet there are four banks used for Pokédex entries. The correct bank is derived from the species ID at the beginning of each entry. (This is the only use that species ID has.)
Three separate routines do the same derivation; `GetDexEntryPointer` in [engine/pokedex_2.asm](/engine/pokedex_2.asm):
```asm
GetDexEntryPointer: ; 44333
; return dex entry pointer b:de
push hl
ld hl, PokedexDataPointerTable
ld a, b
dec a
ld d, 0
ld e, a
add hl, de
add hl, de
ld e, [hl]
inc hl
ld d, [hl]
push de
rlca
rlca
and $3
ld hl, .PokedexEntryBanks
ld d, 0
ld e, a
add hl, de
ld b, [hl]
pop de
pop hl
ret
.PokedexEntryBanks: ; 44351
GLOBAL PokedexEntries1
GLOBAL PokedexEntries2
GLOBAL PokedexEntries3
GLOBAL PokedexEntries4
db BANK(PokedexEntries1)
db BANK(PokedexEntries2)
db BANK(PokedexEntries3)
db BANK(PokedexEntries4)
```
`GetPokedexEntryBank` in [engine/item_effects.asm](/engine/item_effects.asm):
```asm
GetPokedexEntryBank:
push hl
push de
ld a, [EnemyMonSpecies]
rlca
rlca
and 3
ld hl, .PokedexEntryBanks
ld d, 0
ld e, a
add hl, de
ld a, [hl]
pop de
pop hl
ret
.PokedexEntryBanks:
GLOBAL PokedexEntries1
GLOBAL PokedexEntries2
GLOBAL PokedexEntries3
GLOBAL PokedexEntries4
db BANK(PokedexEntries1)
db BANK(PokedexEntries2)
db BANK(PokedexEntries3)
db BANK(PokedexEntries4)
```
And `PokedexShow_GetDexEntryBank` in [engine/radio.asm](/engine/radio.asm):
## `ITEM_C3` and `ITEM_DC` break up the continuous sequence of TM items
[constants/item_constants.asm](/constants/item_constants.asm) defined the 50 TMs in order with `add_tm`, but `ITEM_C3` and `ITEM_DC` break up that sequence.
