DISK Structures

PLATO/CYBIS structures are generally similar but have some important differences. Understanding how these structures fit together is an important first step in how the system works. Some of the most important structures are examined in this section.

NOS Disks contain PLATO/CYBIS structures, wrapped in the form of a NOS Direct Access Permanent File (a.k.a. Masterfile).

NovaNET Disk structures are similar to PLATO/CYBIS structures, with some notable differences.

With the relatively large word size of 60-bits, substructures can be found at the bit level. Most of the significant structures are collected here.

Regardless of the “Container” structure, there are special-purpose packs supported by PLATO/CYBIS.

The following is a list of the known/supported PLATO Pack types and their respective single-letter types (T).

  Filetype   T Description
  ---------- - -----------
  master     a Contains "Master" (operational) copies of PLATO files 
               usually system and published files.
  backup     b Contains "Backup" (non-operational) copies of PLATO files 
  general    c Contains "General" files (usually operational, non-system)
  binary     d Contains system "binaries" (condensed lesson binaries ready for execution)
  archive    e Contains "Archives" of files managed by the archive system.
  

When a user searches for a file, PLATO searches type master and general packs in “Load Order” sequence. This means that files of the same name can reside on multiple packs at the same time and PLATO will simply stop searching once it finds the file on the first pack on which the file resides. The order of this search is managed by the systems programmer and may be viewed using lesson ldr.

The distinctions between these packs and how they are used is operational/semantic in nature. They are, effectively, structured the same with differing operational purposes.

The lesson operator may also be used to view the pack table directly:

1. PLATO Files