One of the features of the message passing layer is the assignment of the identity (id) number to the processes. Each process that participates in the parallel computation is assigned an unique identity number to identify each other throughout execution of the parallel application. Processes use the identity number to send and receive messages from other processes. The master is assigned an id number of 0. The other processes are assigned increasing id numbers 1, 2, ... N-1 (N processes). This identity assignment is done by the initiator processes. When the initiator starts the processes on the remote machine, it gives the identity as a command line argument, which the message passing layer assigns to the processes.