CASIO container format¶

Multiple file formats by CASIO use what has been named a “standard header” by the community. Said header is 32 (0x20) bytes long, and is obfuscated by using bitwise NOT.

The format of this header is the following:

Offset	Size	Field name	Description	Values
0 (0x00)	14 B	File Type (FT)	Type of the file.	See the subsections below.
14 (0x0E)	1 B	Control 1 (C1)	First control byte.	Should be set to `(FS + 0x41) & 0xFF`.
15 (0x0F)	1 B	Reserved		Should be set to `\0`.
16 (0x10)	4 B	File Size (FS)		Big endian 32-bit integer.
20 (0x14)	1 B	Control 2 (C2)	Second control byte.	Should be set to `(FS + 0xB8) & 0xFF`.
21 (0x15)	7 B	Reserved		Should be set to `\0`.
28 (0x1C)	2 B	Obfuscation Options
30 (0x1E)	2 B	Object Count (OC)		Big endian 16-bit integer.

Some subtypes, mostly those for fx-CP and fx-CG models, have a “standard subheader”, which has the following format:

Offset

Size

Field name

Description

Values

0 (0x00)

4 B

Checksum (CS)

Big endian 32-bit integer.

4 (0x04)

1 B

File type (FT)

5 (0x05)

1 B

Target platform (FP)

Value set according to the targeted platform:

Value	Description
`0x00`	fx-CP.
`0x01`	fx-CG (Prizm).

6 (0x06)

4 B

Reserved.

Set to \0.

10 (0x0A)

4 B

Data Size (DS)

Big endian 32-bit integer.

14 (0x0E)

4 B

Control value (C3)

Big endian 32-bit integer.

This should be set depending on the platform to:

For the fx-CP, FS - 0x1000 - 4.
For the fx-CG, FS - 0x7000 - 4.

18 (0x12)

4 B

Reserved.

Set to \0.

22 (0x16)

4 B

Message Zone Size (MZS)

Big endian 32-bit integer.

Unreliable, may and should be set to 0.

26 (0x1A)

6 B

Targeted Add-in Platform (AP)

For C1A, should be set to GY437.

32 (0x20)

28 B

Title (T)

Title or language name.

60 (0x3C)

4 B

File Size (FS)

Big endian 32-bit integer.

64 (0x40)

11 B

Internal Add-in Name (IN)

75 (0x4B)

192 B

Language Labels

8 times a 24 bytes long string.

267 (0x10B)

1 B

e-Activity strip flag (EAS)

Available values are the following:

Value	Description
`0x00`	The e-Activity can’t be used.
`0x01`	The e-Activity can be used.

268 (0x10C)

4 B

Reserved

Set to \0.

272 (0x110)

10 B

Add-in version.

282 (0x11A)

2 B

Reserved.

Set to \0.

284 (0x11C)

14 B

Timestamp

YYYY.MMDD.HHmm-formatted date.

Known types for this container format are the following:

FT (StandardHeader)	FT (StandardSubheader)	Type
`CASIO\0\0\0c2p\0\0\0`	N/A	fx-CP picture
`Ly755 \x2C\0\x01\0\x01\0`	`0x02`	fx-CG f-key files
`Ly755 \x2C\0\x01\0\x01\0`	`0x04`	fx-CG language files
`USBPower\x12\0\x10\0\x10\0`	N/A	fx-9860G language files
`USBPower\x2C\0\x01\0\x01\0`	`0x01`	fx-CG add-ins
`USBPower\x31\0\x10\0\x10\0`	N/A	Main memory archives (fx-CP)
`USBPower\x49\0\x10\0\x10\0`	N/A	e-Activity files
`USBPower\x62\0\x10\0\x10\0`	N/A	Main memory archives (fx-9860G)
`USBPower\x75\0\x10\0\x10\0`	N/A	Main memory archives (fx-CG)
`USBPower\x7D\0\x10\0\x10\0`	N/A	fx-CG picture
`USBPower\xF3\0\x10\0\x10\0`	N/A	fx-9860G add-ins

Todo

Document the \xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF case, in which we need to use the extension instead of the format within the file.