The code ADDA is an open-source implementation of the discrete dipole approximation (DDA), which is a numerically exact method based on the volume-integral formulation of the Maxwell equations in the frequency domain. It can simulate interaction of arbitrary electromagnetic fields with finite scatterers having arbitrary shape and internal structure. ADDA can run both on CPU or GPU, but can also employ a multiprocessor distributed-memory system, parallelizing a single DDA calculation. Moreover, computational complexity of ADDA scales almost linearly with number of discretization voxels (dipoles), which allows one to consider large system sizes and/or fine discretization levels. ADDA is written in C99 and can be used on almost any operating system. It provides a complete control over the scattering configuration, including incident beam, particle morphology and orientation. ADDA can be used to calculate a wide variety of angle-resolved and integral scattering quantities. In addition to far-field scattering by various beams, this includes near fields as well as excitation by a point dipole or a fast electron. Moreover, ADDA can rigorously and efficiently simulate the scattering by particles near a plane homogeneous substrate or placed in a homogeneous absorbing host medium. It also incorporates many DDA improvements aimed at increasing both the accuracy and computational speed. This contribution describes the main features of ADDA and presents several simulation examples.