ABSTRACT
The algorithms dealing directly with the inputting and outputting of analog and digital values are excluded from the group, since they belong to the system software as input-output driving functions. The algorithms are placed at control level of the system and are stored in the field stations or in individual programmable controllers. Algorithms are used in the classical control systems theory for solving control problems in the time or frequency domain. Adaptive control techniques, currently available, are based on measurement at system input and system output. The separate storage of software modules is due to the partitioning of completed application software into the read-only parts, implemented as system firmware, and the restorable and changing parts, pertaining to the process data and the parameters of individual algorithms. In the earlier process control computer systems, the fuctions have been known as input device drivers and have usually been a constituent part of the operating system.
