# Particle Data Commands

The particle data commands are outlined in this chapter.

There needs to be at least one PARTICLE_SEED command. As many PARTICLE_SEED commands as necessary are allowed. Each unique PARTICLE_SEED command defines a distinct set of particles. A USER_EQUATION_INITIAL_CONDITION command is allowed only for pairings of particle seed groups and user equations. Each of the pairings defined by the particle seed commands and the user equations specified by the user_equations parameter in the EQUATION command requires a corresponding USER_EQUATION_INITIAL_CONDITION command. If no equations are specified by the user_equations parameter in the EQUATION command, no USER_EQUATION_INITIAL_CONDITION commands are needed.