Editing File Formats (section)

== PGX ==
This format is a simple, single segment executable, which can be loaded as low as $0200. A PGX is loaded using <code>pexec</code>. <code>pexec</code> treats PGX and PGZ in exactly the same way, and information on how PGZ is handled also applies to PGX.

PGX is similar in scale to MS-DOS’s COM format, or the Commodore PRG format. It consists of a single segment of data to be loaded to
a specific address, where that address is also the starting address.

PGX starts with a header to identify the file and the starting address:

* The first three bytes are the ASCII codes for “PGX”.
* The fourth byte is the CPU and version identification byte. Bits 0 through 3 represent the CPU code, and bits 4 through 7 represent the version of PGX supported. At the moment, there is just version 0. The CPU code can be 1 for the WDC65816, or 3 for the 65c02.
* The next four bytes (that is, bytes 4 through 7) are the address of the destination, in little-endian format (least significant byte first). This address is both the address of the location in which to load the first byte of the data and is also the starting address for the file.

All bytes after the header are the contents of the file to be loaded into memory.