Abstract: A method and apparatus for storing files on a computer file storage device. The files are organized into an hierarchical directory structure. The directory structure comprises directory entries and file entries. The file entries and directory each contain a primary and a secondary pointer. The secondary pointer is initially set to a predefined value. When an entry is to be updated, the secondary pointer is overridden with a value that points to the superseding entry. This directory structure is especially suitable to be used in a write-once computer memory.

Abstract: A system for monitoring combustion of coal in a boiler detects coal composition and heating value using a bulk material analyzer and determines an air/fuel mixture so that when the coal is burned oxygen is available throughout the boiler and the wall temperature of the boiler is maintained below the metallurgical limit and the surface temperature below the ash fusion temperature of the coal where slagging is not desired. The temperature and pressure of steam in the boiler, fuel and air flow rates and temperature and oxygen content of the stack gases are supplied to a boiler model. The boiler model predicts how varying the air supply rate affects sensible heat loss. Periodic measurements of unburned carbon in the ash produced by combustion of the coal are correlated with the operation of the boiler at the time that the ash was produced to provide a basis for estimating unburned coal loss.