A DCOMP software system is developed for calculating a set of composite effective properties from the properties of components and micromechanical parameters. Effective properties of particulate composites, fibrous composites and laminates made from these plies are predicted by the software. Particulate composites containing solid, hollow, encapsulated particles and pores are included in the software. The effect of particle aggregation is also incorporated. Fibrous composites with unidirectional, random inplane or random volume orientation of continuous or short fibres are calculated. Various hybrids can be analysed using multistage calculation. The following set of properties is computed: elastic constants, thermal and moisture expansion coefficients, transport characteristics, dynamic moduli and loss tangents, creep functions, density and specific constants. Classical lamination theory and well-known methods for fibrous composite analysis are utilized in the system. In addition, methods for particulate calculation developed by the author are included. The software consists of the library of computational programs, a user's developed database on material properties and service programs combined with a user-friendly interface. The last has a hierarchical menu system for data flow monitoring, an extensive window system for information display and data entry templates for the user formatted input collection. The software is written in the C language for IBM PCs and compatibles. Executable code requires 190K RAM. The capabilities of the system are illustrated by examples.