1. MPI_Bcast
Bcast stands for broadcast, and is used to send data from one process to all other processes.
The format for this function is: MPI_Bcast(&msg_address,#_elements,MPI_Type, ID, Communicator).
MPI_Bcast (&k, 1, MPI_INT, 0, MPI_COMM_WORLD)
Process 0 sends k to all other processes

2. MPI_Bcast
This function is best used when a some data that a process was using is changed, and it needs to get updated by all other processes in that communicator (ie: the next homework).
Note: A call to MPI_Bcast must be placed where all processes can see it, if not the sending process will block and hang, waiting for an acknowledgement.

3. MPI_Bcast Process 1 Data written, unblock Data Present Data Empty
Write data to all processes
Process 2
Process 3
Process 0
Data Present

4. Simple Program that Demonstrates MPI_Bcast:
#include <mpi.h>
#include <stdio.h>
int main (int argc, char *argv[]){
int k,id,p,size;
MPI_Init(&argc,&argv);
MPI_Comm_rank(MPI_COMM_WORLD, &id);
MPI_Comm_size(MPI_COMM_WORLD, &size);
if(id == 0)
k = 20;
else
k = 10;
for(p=0; p<size; p++){
if(id == p)
printf("Process %d: k= %d before\n",id,k); }
//note MPI_Bcast must be put where all other processes
//can see it.
MPI_Bcast(&k,1,MPI_INT,0,MPI_COMM_WORLD);
printf("Process %d: k= %d after\n",id,k);
MPI_Finalize();
return 0

5. The Output would look like:
Process 0: k= 20 before
Process 0: k= 20 after
Process 3: k= 10 before
Process 3: k= 20 after
Process 2: k= 10 before
Process 2: k= 20 after
Process 1: k= 10 before
Process 1: k= 20 after