ITS PDUMP format
The ITS PDUMP, or pure dump, format was made to allow ITS programs to share virtual memory pages between files, other jobs, and the system.
CREATING A PDUMP FILE
The HACTRN :PDUMP command writes a core image file in PDUMP format.
OVERVIEW
A PDUMP file consists of three sections:
- Page map.
- Data pages.
- Symbol table.
All pages are 1024 (decimal) words.
PAGE MAP
The page map is the first page of the file. The first word is 0 to differentiate it from SBLK files.
After this follow 256 (decimal) page map words.
| 0-27 | 27-35 |
| Access | Absolute or shared page number |
Access bits:
| Bit | Meaning |
| 0 | Absolute (system page) |
| 1 | Do not share file page; make a copy to virtual memory |
| 2 | Shared |
| 18 | Writeable |
| 19 | Readable |
The accumulators are stored in locations 1000-10017 (octal) in the first page.
DATA PAGES
After the page map comes data pages mapped into the address space, in the same order they appear in the map. Absolute and shared pages have no data page. Writable or readable pages do.
SYMBOL TABLE
Just like the SBLK format, after the core image data comes a start instruction, then a symbol table, and last a repeated start instruction.
