The module BlockCalc provides OpenSCADA with the mechanism for creating user calculations, based on the formal language of the block schemes. Languages of the block programming based on the concept of block schemes and functional blocks. Moreover, depending on the block nature, block scheme can be: logic circuits, relay logic circuits, a model of technological process and others. The essence of the block scheme is, that it contains the list of blocks and links between them. From a formal point of view, the block — is an element (function), which has inputs, outputs and an algorithm for computing. Based on the programming environment concept, the block is a frame of values associated with the function object. Inputs and outputs of blocks are to be connected to get the whole block scheme.