TI-73 Link Protocol Guide v1.1 - File formats

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File Formats

The TI-73 Graph Link software stores variables in several types of files. Single variables are stored in files that have an extension that corresponds with their type. Groups of variables are stored in files with the extension ".73g". However, all of these file types have a common format.

The different file types and contents that the TI-73 Graph Link software can read and write are shown below.

Extension | Description
--- | ---
.73g | Multiple TI-73 variables of varying types (group)
.73i | TI-73 picture (image)
.73k | TI-73 FLASH application
.73l | TI-73 list
.73n | TI-73 real number
.73p | TI-73 program
.73q | TI-73 FLASH certificate
.73t | TI-73 table setup
.73u | TI-73 FLASH Operating System
.73w | TI-73 window settings (Window or RclWindow)
.73y | TI-73 Y-Variable (equation)
.73z | TI-73 zoom (saved window settings)

### The TI-73 variable file format

The TI-73 variable file format has two parts: a header and several variable entries.

The header appears at the beginning of the file and takes the following format:
Note - All 2-byte integers are stored little-endian Intel-style (least significant byte first).

Offset | Length | Description
--- | --- | ---
0 | 8 bytes | 8-character signature. The signature is always "`**TI73**`".
8 | 3 bytes | 3-byte further signature. These three bytes always contain {1Ah, 0Ah, 00h} = {26, 10, 0}
11 (Bh) | 42 (2Ah) bytes | Comment. The comment is either zero-terminated or padded on the right with space characters.
53 (35h) | 2 bytes | Length, in bytes, of the data section of the file. This number should be 55 (37h) bytes less than the file size.
55 (37h) | n bytes | Data section - consists of a number of variable entries (described below).
55 (37h)+n | 2 bytes | File checksum. This is the lower 16 bits of the sum of all bytes in the data section.

Each variable entry follows this format:

Offset | Length | Description
--- | --- | ---
0 | 2 bytes | Always has a value of 11 (Bh).
2 | 2 bytes | Length, in bytes, of the variable data.
4 | 1 byte | variable type ID byte (see variable type ID's)
5 | 8 bytes | Variable name, padded with NULL characters (0h) on the right.
13 (Dh) | 2 bytes | Length, in bytes, of the variable data. (This is a copy of the value in offset 2)
15 (Fh) | n bytes | Variable data. Click here for variable data formats.

### The TI-73 backup file format

The TI-Graph Link software for the TI-83 does not have backup capability. However, the calculator itself does. The following format is not readable by TI's software.

Here is the format for backup files that TiLP uses (it's the same format than the TI82/83 one):

Offset | Length | Description
--- | --- | ---
0 | 8 bytes | 8-character signature. The signature is always "`**TI73**`".
8 | 3 bytes | 3-byte further signature. These three bytes always contain {1Ah, 0Ah, 00h} = {26, 10, 0}
11 (Bh) | 42 (2Ah) bytes | Comment. The comment is either zero-terminated or padded on the right with space characters.
53 (35h) | 2 bytes | Length, in bytes, of the backup header and the data sections. This number should be 17 (11h) bytes more than the sum of the lengths of the three data sections as reported in the backup header.
55 (37h) | 11 bytes | The backup header (format described below).
66 (42h) | 2 bytes | Length, in bytes, of the first data section.
68 (44h) | x bytes | First data section.
68 (44h)+x | 2 bytes | Length, in bytes, of the second data section
70 (46h)+x | y bytes | Second data section.
70 (46h)+x+y | 2 bytes | Length, in bytes, of the third data section
72 (48h)+x+y | z bytes | Third data section
72 (48h)+x+y+z | 2 bytes | Checksum. This is the lower 16 bits of the sum of all bytes from offset 55 (37h).

The backup header has this format:

Offset | Length | Description
--- | --- | ---
0 | 2 bytes | Offset to data length: Always has a value of 9.
2 | 2 bytes | Length, in bytes, of the first data section.
4 | 1 byte | Type ID: Always has a value of 19 (13h).
5 | 2 bytes | Length, in bytes, of the second data section.
7 | 2 bytes | Length, in bytes, of the third data section.
9 | 2 bytes | Memory address

###

The TI-73 FLASH file format

It's the same as the TI83+ FLASH file format. You will find it here.

Variable Formats | Table of Contents | Tokens and Characters

Site maintained by Romain Liévin (roms@lpg.ticalc.org) and Tim Singer (tsinger@gladstone.uoregon.edu)