SITS PDUMP format

The Pure Dump format of SITS is a core image file format amenable to paging. Most of the file is divided into 8Kbyte pages, suitable for PDP-11 Memory Management.

The overall structure is: one page with the page table and other metadata, pages with contents for the address spaces, and a symbol table.

Page table

The first page in the file starts with a zero word. This is what distinguishes it from an absolute loader file.

Next comes the page table: 16 words for the instruction space, and 16 for the data space.

The words have this format:

D=I	Absolute			File		Private	Execute	Write	Read				Page Length
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

After the page table comes four words: the starting address, the size of the symbol table in bytes, and the file position of the symbol table as a long word.

The rest of the page is empty.

Content pages

Only pages that are mapped and not absolute have content pages in the file. If a page is both in I and D spaces, the file only has the I copy.

Pages that are shorter than 8K are padded out to a 8K boundary.

Symbol table

After the last content page comes the symbol table. It does not have to end on a page boundary.