MPI_SEND

MPI_SEND(buf, count, datatype, dest, tag, comm) 
[ IN buf] initial address of send buffer (choice) 
[ IN count] number of elements in send buffer (nonnegative integer) 
[ IN datatype] datatype of each send buffer element (handle) 
[ IN dest] rank of destination (integer) 
[ IN tag] message tag (integer) 
[ IN comm] communicator (handle) 

Code            int MPI_Send(void* buf, int count, MPI_Datatype datatype, 
                int dest, int tag, MPI_Comm comm)

MPI_Send specifies that a message containing count elements of a specified datatype starting at address buf is to be sent using the message tag tag to the process ranked dest in the communicator comm. MPI_Send will not return until you can use the send buffer. It may or may not block (it is allowed to buffer, either on the sender or receiver side, or to wait for the matching receive).