Relative Search
A relative search finds text in a ROM when you do not have a table yet.
You type a word that the game shows. In most fonts the letters are stored in
order, so B is one more than A and C is one more than B. mapchar looks
for bytes that differ from each other by the same amounts as the letters of
your word. For each match, it reports which byte is A.
Open Search ▸ Search Window… (Ctrl+Shift+F). The search covers the whole file that is open in the window.
Type a word that you know the game shows, and press Enter.
Use a long word with no repeated letters. KITANA is a good word. OK is not:
a word of two or three letters matches in too many places.
The word can contain:
- letters,
A-Zora-z - digits,
0-9 - kana, あ-ん or ア-ン, in gojūon order and without dakuten. For example, type
ハwhere the game showsバ. -
?, which matches any one character
No other characters are allowed. If the word contains a space, a comma or an
accented letter, the search is refused with a message. Leave these characters
out. For example, for ROUND 1, search for ROUND or for 1.
Upper case and lower case letters are separate sequences, so a word such as
Hello is allowed.
Width is the number of bytes in one character. Start with 8-bit. If nothing is found, try 8 and 16-bit. This setting is slower.
Case gap controls how upper case and lower case relate. When it is on, the
two sequences can be any distance apart. When it is off, a must be exactly 26
more than A. Leave it on.
Limit is the maximum number of results to keep. When the search reaches the limit, it stops and shows a message. A common word reaches the limit quickly. In that case, choose a better word instead of raising the limit.
Stop ends a long search and keeps the results found so far.
| Column | Meaning |
|---|---|
| Offset | The address where the match starts, in hex. |
| Width | The number of bytes per character. For 16-bit, also the byte order. |
| Bytes | The bytes that matched. |
| Bases | The byte of the first character of each sequence: upper is A, lower is a, digit is 0, hiragana is あ, katakana is ア. |
Bases is the result you need. upper=41 means that A is 41, B is
42, and so on.
Click a row to see its bytes in the raw view.
Most results are false matches: bytes that are not text but differ by the same amounts. To find the correct result, check two things:
- The same Bases value appears in several results.
- The bytes around the match also look like text.
For example, upper=41 in four results is the font. upper=9C in one result
is a false match.
Select the correct result and click Build Table from Hit.
A dialog asks which alphabets to add. Choose the sequences that your word identified, or choose Custom… and type the characters in the order the ROM stores them. Each character becomes a table entry, numbered upward from the base.
If a table is already open, mapchar offers to add the entries to it. Click No to create a new table instead.
The new table is not complete. Punctuation, the space, and the byte that ends a string are not part of any sequence. Add them in the Table Editor.
- Try another word. The game may draw that word as a picture, or compress it.
- Try 8 and 16-bit.
- A relative search cannot find compressed text. Use Search ▸ Scan for Text… instead.