PRC (Palm OS)
PRC (Palm Resource Code) is a container format for code databases in Palm OS, Garnet OS and Access Linux Platform. Its structure is similar to PDB databases.[1] Usually, a PRC file is a flat representation of a Palm OS application that is stored as forked database[clarification needed] on the PDA. PRC files are also used by the Mobipocket e-book-reader (here sometimes referred to as MOBI format[2]). The AZW format of Amazon's Kindle reading device is in turn a DRM-restricted form of the Mobipocket format.
On Palm OS, PRC files are used for applications, localized resources (overlays) and shared libraries.[1]
Structure of PRC file
In its essence, a PRC file is similar to a classic Mac OS application. It contains a PRC header, PRC resource headers and PRC resources.[3]
| PRC Header |
| PRC Resource Header |
| PRC Resources |
PRC Header
The PRC header is located at the beginning of the file and contains meta-information on the file:[3]
| Offset | Name | Type | Size |
|---|---|---|---|
| 0x00 | name | char | 32 Bytes |
| 0x20 | flags | integer | 2 Bytes |
| 0x22 | version | integer | 2 Bytes |
| 0x24 | creation time | 32bit integer - PDB Datetime | 4 Bytes |
| 0x28 | modification time | 32bit integer - PDB Datetime | 4 Bytes |
| 0x2c | backup time | 32bit integer - PDB Datetime | 4 Bytes |
| 0x30 | mod_num | integer | 4 Bytes |
| 0x34 | app_info | integer | 4 Bytes |
| 0x38 | sort_info | integer | 4 Bytes |
| 0x3c | type | integer | 4 Bytes |
| 0x40 | creator | integer | 4 Bytes |
| 0x44 | unique_id_seed | integer | 4 Bytes |
| 0x48 | next_record_list | integer | 4 Bytes |
| 0x4c | num_records | integer | 2 Bytes |
PRC Resource Header
For every resource (specified by num_records), there is a resource header containing:[3]
| name | type | notes | size |
|---|---|---|---|
| name | char | Name of the resource | 4 bytes |
| ID | integer | ID number of the resource | 2 bytes |
| offset | integer | Pointer to resource data | 4 bytes |
PRC Resources
Every application contains al least a Code #0 resource with size information and jump tables, a Code #1 resource with executable code and data resources containing pre-initialized values of global variables in compressed form.[3] Other resources that may be contained are forms, form objects, alerts and multimedia data, e. g. images and sounds.
References
- ↑ 1.0 1.1 N. Rhodes, J. McKeehan. Palm OS Programming, Second Edition, O'Reilly, 2001, ISBN:1-56592-856-3.
- ↑ MobileRead Wiki: Reference for the MOBI format
- ↑ 3.0 3.1 3.2 3.3 Theodore Ts'o (2000) The PRC Format. Accessed on 2009-03-07
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